Wikipedia talk:WikiProject Elements/Archive 47

Pentadiamond
Here.
 * I'm sorry. I do not expect to be given a blank homework task. -DePiep (talk) 01:00, 25 July 2020 (UTC)

Categorising copernicium
I propose that we change the colouring of copernicium (112Cn) on our table to "unknown chemical properties". This is because the previous result of copernicium being adsorbed onto gold is, according to this recent article, likely to be due to strong dispersion forces rather than really being a sign that it is homologous to mercury and forming a metal–metal bond. Therefore it is not conclusive as to categorisation after all and all we can really say now is "the experimental evidence is insufficient to tell us what it's really like".

I do not think this will be controversial enough to end up as a megathread. But you never know. ^_^ Double sharp (talk) 08:39, 10 July 2020 (UTC)
 * Hm. Is Cn really so different to Hg that it's best to categorize it neither as a post-transition metal or a transition metal, but as a new group of elements or something? Or is Cn likely either one of the other, but it hasn't been decided yet? Or is it possible that Hg and Cn will be in different categories once the dust settles?  ― Дрейгорич / Dreigorich  Talk  21:04, 10 July 2020 (UTC)
 * In my opinion copernicium is an excellent argument for scrapping our overly complicated and subjective categorisation system and going for blocks only like my userpage does. It appears to have similarities both to radon (as an element) and to transition metals including mercury (when you get it beyond the +2 state). But at the moment it's more that no one really knows yet experimentally what it is. Double sharp (talk) 04:31, 11 July 2020 (UTC)
 * Blocks only, hm. cue He-Ne arguments and a lot of questions about "why isn't He in the p-block?!" from non-technical users.  ― Дрейгорич / Dreigorich  Talk  09:09, 11 July 2020 (UTC) forgot to sign, so this is a... late signature. Oops.
 * Ouch. I've made a wallcovering PT for a highschool. First requirement: show-the-metalloids, and some more categories. I managed to do so while also showing the blocks (as every PT does: as steps). It is in the classroom now, 3.5 m wide. -DePiep (talk) 09:40, 11 July 2020 (UTC)
 * That's just it though. Depending on what you want to emphasise the line can go very far away indeed. Depending on context it may be reasonable to call lead a nonmetal(!). And also depending on context it may be reasonable to call selenium a metal(!). The trouble is that too many resemblances in the p block cut across the boundary. Obviously, it's one of those cases of a continuum. Bismuth is a bit more metallic than antimony, which is a bit more metallic than arsenic, which is a bit more metallic than phosphorus. What are the metalloids? Depends too much on what you want to emphasise. Well, where does metallicity start? I would say antimony because it's the first to have an aqueous cation (Sb3+ exists at highly acidic pH, As3+ does not), and because alloys of antimony with most elements are metallic (that's false for arsenic). But, again, for comparative chemistry of the nonmetals it doesn't make much sense to exclude Sb and Bi from group 15. You see the problem. I just dislike showing the kids something that looks like everything takes its allotted place that way when there are too many ways to move things around.
 * What I would be in favour of is something like Droog Andrey and his colleague's approach. You colour the blocks – which is important to emphasise helium – but you also draw a line separating metals from nonmetals. Of course we also tell the kids that the line is just a rough demarcation: on one side you have more metallicity, on the other side you have more nonmetallicity, but there is a continuum, don't be surprised to see the "wrong" behaviour also common. In which case the last metal in each period should for most average purposes be considered Be; Al; Ga; Sb; At; Og; (E171). (So period 1 has no metals and period 7 no nonmetals.)
 * But, again, I don't want to create another megathread right now. I just want to propose changing copernicium to "unknown chemical properties". Because new information has come in, the original categorisation seems to be questionable now, and we don't know enough to say for sure what it is anymore. Double sharp (talk) 10:09, 11 July 2020 (UTC)
 * I'm not proposing to change that now. We can always put He over Ne while simultaneously calling it s-block. But I think correcting Cn ought to come first. Double sharp (talk) 08:28, 11 July 2020 (UTC)
 * Yes, correcting Cn ought to be first. I still remember that it was colored when it was called Uub.  ― Дрейгорич / Dreigorich  Talk  09:09, 11 July 2020 (UTC)


 * I changed the header: "colour" is not the issue. This is about (what we call in enwiki): categorisation. -DePiep (talk) 21:33, 10 July 2020 (UTC)
 * So noted. Thank you! Double sharp (talk) 08:28, 11 July 2020 (UTC)
 * You guys spelling "colour" and "categorisation", thanks for outing me as an American.  ― Дрейгорич / Dreigorich  Talk  01:58, 11 July 2020 (UTC)

Since there haven't been any objections, I have started to change Cn's categorisation to "unknown chemical properties" across our periodic tables. Double sharp (talk) 06:26, 13 July 2020 (UTC)

I think I got most of them. Could I ask you to change Cn's categorisation to "unknown chemical properties" (so: same colour as neighbouring Rg and Nh) in File:Simple Periodic Table Chart-en.svg? Thank you! Double sharp (talk) 06:37, 13 July 2020 (UTC)
 * Will do. -DePiep (talk) 05:26, 14 July 2020 (UTC)
 * Done. -DePiep (talk) 19:50, 14 July 2020 (UTC)
 * Thank you! Double sharp (talk) 04:44, 15 July 2020 (UTC)

Ref error: IUPAC 2016
There's an error message on all articles transcluding Template:Periodic table because of a broken reference: Harv error: link from CITEREFIUPAC2016 doesn't point to any citation. Harv error: this link doesn't point to any citation. I can't track the problem because the template is nested at multiple levels. Perhaps someone more familiar with the design can sort it out. DrKay (talk) 13:04, 2 August 2020 (UTC)
 * Looking at it. No inline error msg found, not in preview either. Article listed in, harv or sfn cause apparently. -DePiep (talk) 13:28, 2 August 2020 (UTC)
 * In Periodic table legend/Atomic weight: removed . Less elegant, but no error.
 * However, while Periodic table is clean by now, Periodic table still in that category. Will have to research more; cannot do so today. -DePiep (talk) 13:49, 2 August 2020 (UTC)
 * Thanks. The error at Periodic table seems to arise in Template:Periodic table (32 columns, detailed cells). DrKay (talk) 14:01, 2 August 2020 (UTC)
 * Thx. Will take look this week. -DePiep (talk) 14:12, 2 August 2020 (UTC)
 * ✅ for Periodic table (32 columns, detailed cells) too. No errorcat in the article any more. Could be more elegant (use with single book ref). Just ping, User:DrKay, if you find more cases. -DePiep (talk) 11:34, 5 August 2020 (UTC)

Atom FAR
I did NOT nominate this article for FAR-- just doing the nominations that were not done by the editor who did.

User:Kurzon has nominated Atom for a featured article review here. Please join the discussion on whether this article meets featured article criteria. Articles are typically reviewed for two weeks. If substantial concerns are not addressed during the review period, the article will be moved to the Featured Article Removal Candidates list for a further period, where editors may declare "Keep" or "Delist" the article's featured status. The instructions for the review process are here. Sandy Georgia (Talk)  19:28, 14 June 2020 (UTC)
 * Thanks for this notification, User:SandyGeorgia. I'm sure nobody here will blame you for the FAR ;-) -DePiep (talk) 21:18, 14 June 2020 (UTC)
 * :) Sandy Georgia  (Talk)  21:46, 14 June 2020 (UTC)

Black nitrogen (high pressure)
Here.
 * Interesting! I note that helium has hcp, bcc, and fcc phases (last at high pressures), so unfortunately this doesn't shed much light on the question of where to place helium. Double sharp (talk) 03:19, 2 June 2020 (UTC)
 * "Black nitrogen" was ruled out in 2009:  Droog Andrey (talk) 06:28, 8 June 2020 (UTC)

Categorisation
Since polonium in the metalloids-category has been mentioned: actually increasingly I feel that any categorisation colour scheme is going to miss some important things. Just look at the metal-nonmetal boundary. Depending on what kind of comparative chemistry you are doing it may well be worth including even selenium as a metal or, on the other extreme, lead as a nonmetal. There's not a clear boundary. Antimony and bismuth are not true metals but are closer to metals than nonmetals physically; Sb alloys with most other elements are metallic, that is true also for Sn but false for Ge and As. Chemically Sb is about balanced and Bi is more metallic but still extremely weak. Tungsten is physically a great metal and chemically worse than even antimony, Sb3+ cations have more reality than W3+ ones. And then we have the strength of nonmetals which is also fraught. Holistically nitrogen and sulfur are pretty strong, it's more useful to put them with oxygen than not. But then what? Iodine is weaker than them by electronegativity, it is more metallic by far than either. But at the same time it has similar oxidising power to them! (Electron affinity of iodine is higher, but that metric has some issues anyway since negative electron affinity doesn't stop dianions from happily forming in salts: the lattice energy makes it worthwhile.)

So where's the sense in making students believe in a sharp divide? That is not even to mention what horrors we are going to end up with now that copernicium is probably a "noble liquid" held together mostly by dispersion forces like radon – yet chemically still ready to reach +2, +3, +4 using its 6d orbitals once it actually has been ionised.

So perhaps I would suggest colouring by s-p-d-f-g blocks only. Double sharp (talk) 14:28, 12 June 2020 (UTC)



My ideal periodic table for WP. If helium over beryllium is too much, move it to over neon, but still colour it as an s-element. Or maybe plead "positions following electronic structure" and the blocks as an excuse to leave it there. ^_^ Double sharp (talk) 08:42, 14 June 2020 (UTC)


 * "So where's the sense in making students believe in a sharp divide?"


 * We don't make students believe in a sharp divide. In fact, in our periodic table article, we say:


 * "Placing elements into categories and subcategories based just on shared properties is imperfect. There is a large disparity of properties within each category with notable overlaps at the boundaries, as is the case with most classification schemes. Beryllium, for example, is classified as an alkaline earth metal although its amphoteric chemistry and tendency to mostly form covalent compounds are both attributes of a chemically weak or post-transition metal. Radon is classified as a nonmetallic noble gas yet has some cationic chemistry that is characteristic of metals. Other classification schemes are possible such as the division of the elements into mineralogical occurrence categories, or crystalline structures. Categorizing the elements in this fashion dates back to at least 1869 when Hinrichs wrote that simple boundary lines could be placed on the periodic table to show elements having shared properties, such as metals, nonmetals, or gaseous elements."


 * We say effectively the same thing in our articles on metalloids, and nonmetals.


 * The power of boundary overlaps comes from recognizing the interesting chemistry that they flag rather than squabbling about where one class starts and another ends (Schultz 2010). They can be regarded as linch-pins, in addition to horizontal, diagonal, and vertical relationships, that hold together and affirm the facts and parts of the periodic table as a complex structure (Scerri 2012).


 * The key consideration is that our nine categories provide an economy of description and are beneficial to structuring knowledge and to our understanding of the periodic table landscape (Jones 2010, p. 169).


 * For the didactic advantages of organising the metals and nonmetals in this fashion see my article in Foundations of Chemistry (Vernon 2020) with 1,972 accesses, at time of writing.


 * Hinrichs GD 1869, "On the classification and the atomic weights of the so-called chemical elements, with particular reference to Stas's determinations", Proceedings of the American Association for the Advancement of Science, vol. 18, no. 5, pp. 112–124
 * Jones, B.W.: Pluto: Sentinel of the Outer Solar System. Cambridge University, Cambridge (2010)
 * Scerri, E.: A critique of Weisberg’s view on the periodic table and some speculations on the nature of classifications. Found. Chem. 14 (3), pp. 275–284 [282–283] (2012)
 * Schultz, E.: Reflections catalyzed by an assault on a favorite principle. Journal of Chemical Education. 87 (5), pp. 472–473 [473] (2010)
 * Vernon RE 2020, "Organising the metals and nonmetals", Foundations of Chemistry, vol. 22, pp. 217–233, open access

--- Sandbh (talk) 04:51, 19 July 2020 (UTC)

Metallization pressure
I guess Draft:Metallization_pressure should be wikified before publication. Droog Andrey (talk) 19:56, 5 June 2020 (UTC)
 * Maybe we could incorporate some old stuff from the Nonmetal article before it was rewritten, which I saved at User:Double sharp/Metallic nonmetals. ^_^ Double sharp (talk) 04:17, 6 June 2020 (UTC)
 * P.S. If this is about metallicity in the physical sense, then shouldn't Sb and Bi be there if we put C and As in? They are semimetals in that sense. Double sharp (talk) 04:22, 6 June 2020 (UTC)
 * I'm not sure about Bi. Droog Andrey (talk) 13:32, 7 June 2020 (UTC)
 * Bi becomes a semiconductor under pressure: Droog Andrey (talk) 15:15, 10 June 2020 (UTC)
 * P.P.S. The opposite phenomenon is also interesting. At 200 GPa Na becomes an insulator (10.1080/08957959.2010.508877). ^_^ Double sharp (talk) 04:27, 6 June 2020 (UTC)
 * But at higher pressures it turns to metal again :) Droog Andrey (talk) 13:32, 7 June 2020 (UTC)


 * That data would be nice to see in PT extract form.
 * Possible metallization of N > 280 Gpa: Gregoryanz, E., Goncharov, A. F., Hemley, R. J. and Mao, H.-K. (2001) Phase diagram of nitrogen at high pressures and temperatures. In 18th Int. Conf. High Pressure Technology (Joint Conf.: AIRAPT-18 and HPCC-11), Abstracts, p. 21; Phys. Rev. B, 64, 052103/1–4 (2001), ibid, 66, 22418/1–5 (2002)
 * Carbon: Vereshchagin, L. F., Yakovlev, E. N., Stepanov, G. N. and Vinogradov, B. V. (1972) Possibility of transition to metallic state in diamond. Pis’ma, Zh. Eksp. Teor. Fiz., 16, 382–383 Vereshchagin, L. F., Yakovlev, E. N., Vinogradov, B. V., Sakun, V. P. and Stepanov, G. N. (1973) Transition to metallic state in diamond. Pis’ma, Zh. Eksp. Teor. Fiz., 17,422–424 Yao, B., Ding, B. Z., Li, D. J. and Hu, Z. Q. (1994) A discussion on a new phase in polycrystalline diamond. In High Pressure Science and Technology-1993, eds. S. C. Schmidt, et al., pp. 507–509, N.-Y.: AIP Press Whittaker, A. G. (1978) Carbon: a new view of its high temperature behavior. Science, 200, 763–764
 * Argon: expected at 430 Gpa, Phase Transformations of Elements Under High Pressure – E. Yu Tonkov, E.G. Ponyatovsky, p. 209
 * --- Sandbh (talk) 23:41, 6 June 2020 (UTC)
 * Thank you! Droog Andrey (talk) 13:32, 7 June 2020 (UTC)
 * Any reliable sources about fluorine? Droog Andrey (talk) 15:47, 14 June 2020 (UTC)
 * is not a real prediction, but just a speculation that MP(F) should be much higher than MP(Cl). Droog Andrey (talk) 06:26, 15 June 2020 (UTC)
 * I'm aware, I put it as a placeholder figure as long as we can't find anything better. It may of course be removed as not being a really rigorous prediction. Double sharp (talk) 06:29, 15 June 2020 (UTC)

Kurushkin (2020): He over Be
"Helium’s placement in the Periodic Table from a crystal structure viewpoint" (open access) here.

Review This is a fine example of a boutique article. Short, to the point, and for its focus on just one consideration, nicely fleshed out.

Clever as it is, I feel Kurushkin does not do himself justice on several points.

1. He says:


 * "Whichever representation of the periodic system is argued to be the optimal one (Leigh, 2009; Scerri, 2009), consistency of representation is the criterion that has to be met."

It is debatable whether there is such a thing as an optimal representation of the periodic system, and whether consistency of representation needs to be met. For example, the chemistry of silver is largely that of a main group metal yet we continue to categorise it as a transition metal, simply because it’s in the d-block.

2. That the IUPAC Periodic Table has four blocks of chemical elements: the s-, p-, d- and f blocks, does not mean that, as Kurushkin, says, "its whole body is based on electron configurations."

I argue that the IUPAC table is based around practical chemistry, and the fact that four blocks can be discerned shows that chemistry has a pretty good basis in electronic configurations. There is nothing inconsistent about placing He above Ne on a chemistry basis. Equally, in this context, there is nothing so egregious about a 15-element wide f-block.

3. Kurushkin’s questions about (a) state of matter; (b) temperature; (c) pressure and (d) allotropes, are distractions. To compare physical and chemical properties, the table can be based on the most stable form of the elements in ambient conditions. On this point I note that white P is taken as the representative form of P, even though this is its most unstable form. So, there is another fly in the ointment that has hardly ever raised any concerns about inconsistency. Of course, now that black P can be easily prepared, there’s no longer any fundamental reason to regard white P as the standard form.

4. He goes on to to ask if, in the solid state, would we still support the idea of putting helium above neon because they are both noble gases?

The answer is, we would since He as a solid is a monatomic, close-packed, soft, easily crushed insulator held together by London forces, as is the case for all the noble gases.

5. He says:


 * "Next, it might be considered surprising that solid helium, beryllium and magnesium all have the same crystal structure...which is hexagonal close packed (h.c.p.); while neon, argon, krypton and xenon all have a face-centred cubic (f.c.c.) crystal structure."

The relevance of this observation is underdone. Equally, we do not move Be and Mg in group 2, over Zn and Cd in group 12 because all four metals are hcp, and they all have s2 valence electrons. Clearly, the noble gas nature of helium and the position of He-Ne as the extreme diagonal counterparts of Cs-Fr are taken to mean so much more.

6. While Kurushkin relies on hcp helium, there are three known forms of solid helium:
 * alpha (hcp): low-temperature form at ~0.95 K and > 25.3 atm
 * beta (bcc): lower density, higher temperature form at 1.47 to 1.76 K and 26 to 29.75 atm.
 * gamma (fcc): high-temperature high pressure form at 14.9 K and 1106 atm.

How does one decide which is the benchmark form of solid helium? I’d like to see some clear air between these options.

7. Mention of Na2He does not help, nor do purported entities such as FeHe, FeHe2, FeO2He. Many things become possible in exotic conditions. There is no loss of electrons, hybridization, or bonding by helium.

For He in Be, Bakai et al. (2011) find, using ab initio methods of simulation, there is some hybridization of electron states between helium and the nearest beryllium atom. The helium binding energy is about 5.6 eV. This is well within the range of chemical bonding energies, as I understand it. As they say, "A cloud of electron density formed between helium and beryllium indicates a covalent character of the chemical bonding."

This was news to me. It didn't seem to have registered with the chemistry establishment.

A reservation about He in Be is whether or not It could be regarded as an isolable compound. Without a surrounding matrix of Be atoms, I presume it would break apart. How do would you measure its properties etc.

According to Yang et al. (2016), the solubility of helium in beryllium is very low. A possible reason may be the fairly high atomic density of Be which makes interstitial helium energetically unfavourable. I don’t know how this accords with Bakai et al.

8. If helium (Z =2) was to be moved over Be, does that spell the end of H (Z =1) over C as advocated by Cronyn, or over F as Sacks (2006) championed (https://link.springer.com/article/10.1007/s10698-005-9003-5)?

9. I’m reminded of Jensen’s critique of Hg as a transition metal based on the purported isolation of HgF4 (never confirmed):


 * "...what is the proper ontological status in a descriptive inorganic course of highly reactive transient species formed under extreme conditions and how should one evaluate their importance relative to the periodic table?"

*         *          *
 * "From the statistical point of view, we note that only one of the three important members of Group 12 shows a possible involvement of the (n-1)d subshell in its chemistry and then for only 1/1000th of its known chemistry under extremely atypical conditions. Our choice then is between labeling this group as transitional and treating the behavior of 2/3 of its members and of 99.9% of their known chemistry as exceptions to this label or continuing to treat this group as main-group with only 1/1000 of the known chemistry of one of them as an exception. I think the optimal choice is rather obvious."

*        *          *
 * "In short, whether this synthesis is or is not confirmed, for the present at least (since history teaches us that chemistry always has its unpredictable surprises), its practical consequences for how we view and use the periodic table are essentially negligible."

I still like Kurushkin’s article, even so. --- Sandbh (talk) 01:21, 16 June 2020 (UTC)
 * I have no problem with He over Be spelling the end of H over C or over F because I consider those placements undesirable in the first place: H should be over Li due to electronic configurations. Those, taken across all chemical compounds, should be considered the important thing, because otherwise there are too many considerations and it is hard to get a full consistency. Otherwise you'll be spending forever arguing against Be-Mg-Zn, B-Al-Sc, Ti-Zr-Ce-Th, with arguments that have to be narrowly circumscribed to avoid tearing at each other's throats for the next issue. H and He simply have one and two valence electrons respectively, they have to go over Li and Be. Their anomalous properties simply show the huge first-row anomaly for the s-block, which is even higher than that for the p-block. Whereas, He over Ne is not right for a first-row anomaly. Neither is H over anything but Li. (In fact, putting H over B is an excellent way to make the first-row anomaly trend not work.)
 * Now I just quote my draft supporting helium over beryllium from User:Double sharp/Idealised electron configurations. When I wrote it I considered the placement of H over anybody other than Li or F too chemically ridiculous to need comment, but I have now added over there something to address that. Which is a one-sentence "Due to H having one valence electron and one valence vacancy, the only elements it makes any sense put over are lithium (one valence electron, seven vacancies) and fluorine (seven valence electrons, one vacancy)".


 * 1) Placement of elements is about electronic structure that explains chemistry, not about correlations in the final chemical behaviour that is a lot of steps removed from the origins even if still related. Otherwise we have trouble explaining nitrogen and bismuth in the same group: N is strongly nonmetallic, Bi is definitely metallic (even if a weak metal), and the oxidation states favoured are different (N: +5/-3, Bi: +3).
 * 2) Atomic properties show the trends (graphed in Grochala's article and here) where He-Ne fits quite badly but He-Be fits sensibly as a first-row anomaly (as well, if you graph the noble gas trend, Ne-Ar looks like the stereotypical first-row anomaly, and not He-Ne).
 * 3) The knock-on effects on the following elements. The He-Ne difference actually explains why Li, despite being not exactly the most reactive alkali metal (translation: it's the least reactive one), is actually the most electropositive one, because 1s shields so well from the nucleus to a level that 2p-6p cannot manage (10.1002/jcc.20522). He over Be emphasises the range of applicability of the "duet rule" for the filled 1s2 subshell, and by its placement it shows clearly that this is something different from the octet core of the other noble gases.
 * 4) The first four elements (H through Be) are all s elements; if we are serious about blocks as a guiding principle, we have to consider He-Be primary periodicity and He-Ne secondary periodicity, like H-Li vs. H-F, because H-Li and He-Be are pairs from the same blocks and H-F and He-Ne are not. Yes, it's true, we don't teach the blocks from the start, but we still use them as our guide to how to place elements despite that and I think making an exception for helium is not right. It smacks of special pleading and immediately opens questions for B-Al-Sc-Y-La, Ti-Zr-Ce-Th, Be-Mg-Zn-Cd-Hg, Ca-Sr-Yb, and other wonderful denizens of Pandora's box. I would rather keep the box shut with the lid of consistency, even if chemically strange-looking He over Be is the price for that. We can explain its really weird behaviour for an s element by saying that it has been impacted by (1) lacking any shielding from the nucleus and (2) lacking a p-subshell. This is exactly like hydrogen, which we place standardly in group 1.
 * 5) Helium stands in relation to beryllium more or less as hydrogen stands in relation to lithium, and the latter is more or less standard by now. So if you think the latter is all right, with a nonmetal heading group 1 with some incipient metallic properties, than the former doesn't look quite so strange anymore. Though I freely admit that incipient metallic properties of helium are even weaker than those of hydrogen, but at the very least the huge first-row anomaly it represents now looks like something regular rather than saying "hydrogen is our weirdo". The general s block trend is for chemical activity to increase down each group as the valence electrons get farther from the nucleus; well, H-Li and He-Be certainly fit that.
 * 6) I dislike having to cut off hydrogen (and maybe helium) from the periodic law. If it is supposed to be absolute, and we make an exception right at the very beginning, it smacks of special pleading again. OK, maybe we have some exceptional cases at the beginning, but they should form some part of the normal trend and just represent a coincidence of various different groups. You can think of it as something like an exceptional isomorphism going on here, to use a mathematical analogy.
 * 7) This fits neatly with the principle of first-element distinctiveness (that, according to Henry Bent, a long-term He-Be advocate, goes back to Mendeleev himself). And it also fits with Jensen's principle of first-row anomalies, s >> p > d > f. I find most of Bent's arguments (mostly involving stuff like atomic number triads etc.) unconvincing but this one is an exception because it corresponds to real chemistry. Whereas there is nothing really distinctive about helium over neon, not to mention how it breaks reactivity and electronegativity trends.
 * 8) With helium in group 2, every main group starts with nonmetal(s) and then gets metallised. The faster metallisation for the s block fits with Jensen's principle of first-row anomalies, too. And it makes sense: just like 2p, 1s is really really small, nuclear attraction is huge, so Kaupp's explanation for the electronegativity dropping precipitously down from 2p to 3p also applies just as well from 1s to 2s! It even applies better because 1s shields even better than 2p! Such a trend is seen for H-Li and He-Be, but H-F and He-Ne instead increase electronegativity going down! It also means that a small 1s or 2p element should be bad at multicentre bonding (and metallic bonding is kind of the generalisation as the number of centres goes to infinity).
 * 9) The regularity is then that as we progress down an s-block group, our valence set expands. In 1s it's out of 2 electrons; in 2s and 3s it's out of 8; in 4s and 5s it's out of 18. (Unfortunately expansion to 32 for 6s and 7s seems to need pressure.) So in some sense we should expect He-Be as something not too different in nature from Mg-Ca (where Ca starts showing some serious d involvement), even if it is obviously of a once-in-the-entire-table scale (because when else do you have a first-row anomaly in an odd period, therefore implying that there's no homologous period after it without the first-row anomaly)? The general situation (due to kainosymmetry – yes, that's also from Shchukarev) is for the even periods to behave differently from the odd ones, with period 1 standing apart from both. (Because even periods have an orbital without radial nodes that creates incomplete shielding. Even periods have stronger oxidisers and suffer more significant contraction effects, because their size increase from the previous period has been cancelled.) Well: period 1 is absolutely unique, as it's an odd period without a partner and with kainosymmetry. So, the bad resemblances of H-Li and He-Be are in fact totally regular. H-F and He-Ne, which look better at first glance, would actually be unexpected in their relative goodness. Although I'm aware that this argument is dangerously close to saying "He-Be is correct because it is wrong". XD
 * 10) The difference also explains why He is more reactive than Ne: Ne chemistry is thwarted by lone-pair repulsion (that affects F2 for instance, and is a reason why the 2p elements favour multiple bonding), and just like what happens with H+ (immense polarising power of a naked proton) and H&minus; (a rather diffuse anion because the lone proton cannot easily manage this much negative charge), any disturbance of the filled 1s2 subshell of helium instantly increases reactivity significantly, as Grochala noted in his PCCP paper on (HeO)(LiF)2 (supplementary information).
 * 11) The stability of He compounds in predicted Ng-Be bond-containing compound series (Ng = He, Ne, Ar, Kr, Xe) drops off the clear trend from Ne-Xe. Instead He appears near Ne, and sometimes the He compound is even less unstable than the Be compound. (Grandinetti, Noble Gas Chemistry, p. 74) By changing the ligand you can change the order of He vs. Ne (nothing is said about Ne-Xe, presumably it follows the standard order throughout), which suggests that He is to some extent an accidental part of the noble gas trend. (Grandinetti pp. 103ff.)
 * 12) Theoretically predicted He bonds not only lack Ne analogues, but are also significantly analogous to Be.

I realise the last three are weak arguments because He compounds are quite outside the bounds of "normal chemistry", but the others are not.

I won't deny that at least partly my support of He-Be started as a provocation. Everyone's knee-jerk reaction is "that's nonsensical", I suppose, but trying to pin down exactly why it is so sheds some light on what the bases of the PT are usually felt to be. Maybe indeed H-Li and He-Be are not the best placements for students learning chemistry for the first time, but once subshells are introduced, the students should be ready for it.

(It goes without saying that since by the time people seriously deal with f and d block chemistry they are not beginners anymore, I still see no good reason for Sc-Y-La. ^_^)
 * Double sharp (talk) 03:04, 16 June 2020 (UTC)

Top million substances
Hello, I’m working with User:Egon Willighagen from Wikidata and others to compile a list of what we consider to be the one million most important chemicals. This list will be used to prioritize what we look at for both Wikidata and Wikipedia, and possibly other external groups that interact with us. These chemicals could include things like the elements and other basic substances you would encounter in your chemistry education, chemicals encountered in everyday life (e.g. in detergents, food additives or hair gel) as well as more niche substances such as pharmaceuticals, polymers, pollutants, biologically important materials, etc. Are there any specific collections of substances you would recommend us to look at? Please post any suggested lists or databases below.

Obviously I'm posting this on WT:Chemicals, etc. We're including all known elements, but I'm posting here to make sure we don't overlook things like important isotopes (such as Tritium). Many thanks, Walkerma (talk) 18:21, 19 June 2020 (UTC)


 * what do you have in mind with a million of chemicals? For instance, there are elements whose chemistry is entirely unknown, and moreover, nobody even wants to even try to examine it because it's hard and there are more interesting elements to try. Are those a part of the one million most important chemicals? A similar question for nuclides: there are many radioisotopes used in medicine; do those count? Why though if they do, since chemistry of a specific isotope is often negligible compared to the element in its natural isotopical composition?--R8R (talk) 19:30, 19 June 2020 (UTC)

It's very much a judgement call, and from my time with WP:1 I'm aware that importance is quite subjective, but any suitable lists would be helpful. such as "top 40 radioisotopes used in medicine". I think we'd want to include radioisotopes that are widely used (in medicine, e.g., Fluorine-18, or major ones used in nuclear reactors or in smoke alarms). Likewise, stable isotopes that are important such as carbon-13 for NMR. But certainly not every isotope that's ever been tested for use in medicine! Thanks, Walkerma (talk) 19:43, 19 June 2020 (UTC)


 * radioisotopes used in medicine are listed in Therapeutic radiopharmaceuticals and Diagnostic radiopharmaceuticals. -DePiep (talk) 11:02, 21 June 2020 (UTC)
 * Thanks - that's a useful specialist list! Walkerma (talk) 20:48, 21 June 2020 (UTC)

Introduction
It's curious to note that if H (2.1 Pauling electronegativity) is placed over B (2.0) and Al (1.5), and if these three are then moved over group 3 as Sc-Y-La-Ac, there is a steady decrease of EN going down group 13, from H to Ac.

Pauling showed his electronegativity table with B-Al over Sc, and H in a floating position, aligned with Mn—a tip of the hat to Mn’s half-filled 3d sub-shell (1988, p. 182).

I note:
 * +1 is known for all members of the resulting hybridised group, H-B-Al-Sc-Y-La, except for Ac
 * In reactions of Sc+, Y+, La+ and Lu+ with H2, D2, HD, CH4, and C2H6 the Lu+ system was found to be rather different from the other three systems in several respects, including electron configuration, reactivity onset, thermodynamic behaviour, and interactivity mechanism. Sc, Y and La showed properties consistent with periodic trends. The different behaviour of Lu was attributed to an indirect effect of its 4f14 sub-shell (Elkind et al. 1989; Sunderlin & Armentrout 1989).

Splitting the p-block in such a manner would be controversial.

H could instead be placed on top of B in group 13. There is a precedent with He in the p-block. That would result in all non-metals being located in the p-block. The shape of the periodic table would take on the appearance of a tower, wall, keep, and dungeon, as shown.

I then note: References --- Sandbh (talk) 08:20, 12 June 2020 (UTC)
 * H (Z =1) is half a pseudo-octet from B (Z =5)
 * a progression in metallic character, from a weak non-metal (H), through a metalloid (B), via two weaker amphoteric metals (Al-Ga), to two metals (In, Tl)
 * H is clearly molecular; B is network covalent (mean CN 6.6); Al has interatomic bonding that is partially directional in nature (CN 12); Ga is a molecular metal, having a CN of 7 (i.e. 1+2+2+2); In has a partially distorted structure associated with incompletely ionised atoms and has a bulk coordination number of 4+8; Tl has a close-packed structure (CN 6+6) but an abnormally large inter-atomic distance that has been attributed to partial ionisation of the Tl atoms.
 * +1 is known for all members of the resulting hybridised group, H-B-Al-Ga-In-Tl
 * On the analogy between B and metals, Greenwood (2001, p. 2057) commented that: "The extent to which metallic elements mimic boron (in having fewer electrons than orbitals available for bonding) has been a fruitful cohering concept in the development of metalloborane chemistry…Indeed, metals have been referred to as "honorary boron atoms" or even as "flexiboron atoms". The converse of this relationship is clearly also valid…"
 * an extensive chemistry between H and B i.e. the boranes BxHy, their anions BxHy–, and related cations e.g. H2B(base)2+ (Miller & Muetterties 1964)
 * the triangular H3+ cation is the most prevalent form of H in the universe; B can form triangular B32– and B3+ rings [1][2]
 * a diagonal relationship between H and C (Vernon 2020)
 * carborane chemistry, BC2Hn+2
 * all elements of the group are capable of forming alloys.
 * Elkind, J.L., Sunderlin, L.S., Armentrout, P.B.: Periodic trends in chemical reactivity: reactions of Sc+, Y+, La+, and Lu+ with H2, D2 and HD. J. Phys. Chem. 93, 3151–3158 (1989)
 * Greenwood NN 2001, 'Main group element chemistry at the millennium', Journal of the Chemical Society, Dalton Transactions, issue 14, pp. 2055–66
 * Miller N. E., Muetterties E.L. 1964, “Chemistry of boranes. X.1,2 borane cations, H2B(base)2+”, Journal of the American Chemical Society. vol. 86, no. 6, pp. 1033-1038
 * Pauling L 1988, General chemistry, Dover publications, Mineola, NY
 * Sunderlin, L.S., Armentrout, P.B.: Periodic trends in chemical reactivity: reactions of Sc+, Y+, La+, and Lu+ with methane and ethane. J. Phys. Chem. 93, 3151–3158 (1989)
 * Vernon RE 2020, Organising the metals and nonmetals, Foundations of Chemistry
 * I see from your second point that apparently unusual oxidation states like +1 for Sc, Y, La, Lu are admissible for you when they can be used to support Sc-Y-La, but not when I argue for constant +2 as the "get rid of the s electrons alone" baseline to support Sc-Y-Lu. Meanwhile, just compare B-Al-Sc with B-Al-Ga, and see how the 3d10 shell in Ga makes its chemistry significantly less like aluminium's than scandium's is. The argument when applied to chemically relevant species rather supports B-Al-Sc. Of course, that's only because it doesn't take the global view that this sort of thing happens every time a block finishes, it's part of the general even-odd symmetry of the periodic table. Compare 2p, 4p elements with 3p, 5p elements, you'll see it immediately. It's the same as comparing 3d with 4d or 4f with 5f. If you allow B-Al-Sc, suddenly C-Si-Ti-Zr-Ce-Th also looks reasonable.
 * Well, you have a lot of arguments here, for two solutions that absolutely nobody else seems to support as they have hydrogen over boron. Which chemically doesn't make any sense just looking at oxidation states. And so much, incidentally, for the argument that changing group 3 to show Lu in it will be a seismic move that is fighting a gigantic chemistry battleship: if that was so, H over B is certainly fighting a Yamato-class battleship as a single swordsman with no backup, whereas Sc-Y-Lu has a large backup fleet behind it ready to take on a much smaller and less certain battleship.
 * The fact that you can make those arguments just shows that if you try hard enough (a "pseudo-octet", really?) you can support any placement whatsoever because any two elements will have some similarities. Here, let me throw some out. Helium has electronegativity less than oxygen (He-O bond in (HeO)(LiF)2 has partial positive charge on the helium), we may therefore place it over nitrogen as the electronegativities are probably similar and to compare it with nitrogen's nobility in the elemental state and since those two elements are the standard cryogenic liquids. Or we may place it over carbon since HeC2+ is expected to be stable, we have a half real (not just pseudo) octet between He (Z=2) and C (Z=6), whereas HeN2+ is not, and then call He-N a diagonal relationship. Oh, and the 0 oxidation state is known for helium and also for oxygen in HOF, maybe we should put them together in the same group since He seems to have some chemical affinity for O too. And atop any column helium will represent an extreme in nonmetallic character anyway. Or maybe we should float H, He, and Li altogether to keep the BBN elements together, they may even have formed theoretically stable linear HLiHe+. Putting helium over oxygen also means that the lookout window on the p-block tower is placed nicely in the centre rather than at one end. No, I don't buy any of the arguments I've just come up with. But how different are they from yours? Where's the sense in the argument "all elements of the group are capable of forming alloys"? That will be true of any group I come up with by shoving the symbols of the metallic (including antimony, BTW) elements in a hat and drawing six times without replacement. Or even with it.
 * One has to pick what important criteria to start from and then be consistent about them with no prejudice as to the outcome. And if the result is not what you want, then you'd better be consistent and either accept the changed result or revamp the criteria. I chose elements in all compounds, the fundamental thing chemistry is examining, and the subshells the valence electrons are in, they who control each element's personality. This, on the other hand, reads to me as out-of-context trivia that sometimes needs weird conditions (Sc, Y, La, Lu +1) and can equally well support just about anything.
 * Still with the utmost respect, I believe you can come up with better reasoning. Double sharp (talk) 13:15, 12 June 2020 (UTC)

Follow-on
I criticised your position of a +2 baseline to support Sc-Y-Lu on the grounds that the most common oxidation state for the transition metals was +3 for six of ten of them, rather than +2; and that +4 is the most common oxidation state for the 4d and 5d metals. I've since learnt that ionising away the s electrons is a rather vacuous distinction since the s orbitals in the transition metals are barely occupied.

My idea originated with the observation by Cronyn (2003) that H and C have comparable electronegativity values (2.1, 2.5) and that on this and other bases (inc. IE and EA), H would be better placed over C. I had always wondered about this given the EN of H, at 2.1, was much closer to that of B, at 2. And the EA of H (73) is closer to that of B (27) than to C (122).

I've seen references to positioning H midway over B and C. Thus, this is the practice adopted by Sanderson (1967, passim), and Silberberg (2017, p. 391). When I saw Pauling's EN table, that catalysed my thinking. In this context I don't agree with your assertion that "absolutely nobody else" seems to support H over B.

Looking through Sanderson's book he gives figures for the partial charges on O, S, F, Cl, Br, and I atoms in binary oxides, sulfides, and the halides. In all cases the trend is better with H over B. Frex, the partial charge on O going down group 3 is H −0.25, B −0.24, Al −0.31 Ge −0.19, In −0.23, and Tl −0.21. Down group 4 is it is H −0.25, C −0.11, Si −0.23 Ge −0.13, Sn −0.17, Pb −0.18. I have to read more to see how he worked this out.

Does anyone seem particularly bothered that He could not form a compound of o/s > +2, yet e.g. Xe and Rn can? No. Or that F does not form an o/s > +1 whereas all the other halogens do? No.

Placing H with its typical +1 oxidation state over the group 13 metals with their generally +3 oxidation states is less egregious than Cronyn placing it over group 14, with their generally +4 to +2 oxidation states. At least I can say that +1 becomes more stable going from B to Tl such that monovalent Tl is the preferred oxidation state. The halides form B(I) derivatives; B4Cl4 is well characterised. In MgB2 there is a charge of −1 on each B atom. Al(I) chemistry is rare but there is enough of it to support its own Aluminium(I) article. For Ga and In there are e.g. Ga2Y (Y = O, S, Se); red InCl (mp 225°C), InI[InIIITe2] and InI[In3Y3] (Y=Se, Te).

As there is no IUPAC project looking at the position of H, I anticipate no need for a game of giant battleships. I'm making a contribution to the literature, per the example set by Cronyn (40 citations).

Half a "pseudo-octet"(?), yes really. I've seen the expression pseudo-octet used to refer to, for example, (inert shell) stabilisation in tetrahedral semiconductors as each core sees contributions from eight valence electrons (on a shared basis). I take your point however: I can simply say, "half an octet".

Like you I don't support any of the superficial arguments you came up with regarding the positioning of He, except for He being half an octet away from C.

The sense of the argument that all of H-B-Al-Ga-In-Tl form alloys with metals is partly to address the perception that H does not seem to be much of a metal, and partly to note its capacity to form alloys (with TMs) is a property it shares with B. I don't need to select only the "metallic" elements from e.g. group 15 in order to pull six out the bag. I further note H can stand-in for alkali metals in some compounds whereas this is not the case for C.

I make mention here of the metal borohydrides, and their structural similarities with the metal oxides, and that the tetrahydridoborate, BH4–, and the oxide, O2–, anions are isoelectronic, both carrying 10 electrons. The metal borohydrides are known for all categories of metals.

I note the hydronium cation H9O4(+) and the pentaborane anion B5H8(−) are isolectronic.


 * [[File:Dodecaborane-3D-balls.png|thumb|250px|The dodecaborate anion ([B12H12]2−) was discovered by Pitochelli and Hawthorne.]]

As a passing reference, since I don't yet understand most of it nor its significance, Hawthorne recently noted that the dodecaborate ([B12H12]2−) ion could be "tuned" to give it the properties of many different metals.

One does not have to pick what "important" criteria to start from. One can make an observation and proceed from there to see if other observations, including those made in the literature, are supportive. That's what I did in this case, rather then deciding some such observations are to be regarded as trivia.

I see H over B yields an honorary metal line (near-metalloids, if you will) passing through H-Rn, as follows:

H B C Al Si P Ga Ge As Se In Sn Sb Te I Tl Pb Bi Po At Rn

H: "Honorary metal in many versions of the activity series" (Chang 1998, p. 151) C: Lustrous appearance; behaves electrically like a metal (conductivity ~ that of iron at room temperature); band structure of a semi-metal P: "We have declared phosphorous an honorary metal for the purposes of this monograph…" (Silver and Walden 2012, p. 2) Se: Lustrous appearance; crystalline structure thought to include weakly "metallic" interchain bonding; counted as a heavy metal I: "…it is now clear that liquid metal embrittlement (if we may regard iodine as an honorary metal for present purposes…" (Cahn 1992, p. 279) Rn: Cationic behaviour

That's all for now. Thanks for prompting me to clarify my position. Sandbh (talk) 03:58, 14 June 2020 (UTC)

References
 * Cahn RW 1992, Artifice and artefacts: 100 essays in materials science, Institute of Physics Publishing, Bristol
 * Chang RW 1998, Chemistry, 6th ed., McGraw-Hill, Boston
 * Cronyn MW 2003, "The proper place for hydrogen in the periodic table", JChemEd, vol. 80, no. 8, pp. 947−950
 * Sanderson RT 1967, Inorganic chemistry, Reinhold, New York
 * Silberberg MS 2017, Chemistry, 8th ed, McGraw Hill, New York
 * Silver S and Walden W (eds) 2012, Metal ions in gene regulation, Springer, Dordrecht
 * Double standard, again. Is +1 in any sense the most common oxidation state for any of the metals Sc, Y, La, Lu you mention when using +1 as an argument against Sc-Y-Lu? No. Why's that a valid criticism against the "common +2 state" argument and not a valid criticism against yours?
 * Putting H floating above B and C doesn't mean that the authors think it has anything much to do with boron unless they say so. Rather it likely means that they are just floating it around because they don't think it fits well in any group.
 * Arguing for H over B on the grounds that +1 becomes more stable as you go down is basically not understanding trends at all. +1 is most stable at the bottom of the group. So you want to put H, with only +1 and also −1 states, at the top of the group?
 * And you miss my point. I can equally take a silly group like {Na, Be, Pr, Sb, Nb, U}. And all six of those elements still form metallic alloys (including antimony). We even nicely go up in oxidation states as we go down the "group". Is that an argument for it? No. So how is that an argument for {H, B, Al, Ga, In, Tl}?
 * "As there is no IUPAC project looking at the position of H, I anticipate no need for a game of giant battleships." Surely that supports exactly what I was saying. Relooking at the position of hydrogen is apparently so much off everybody's radar that IUPAC sees no need to address it. But relooking at group 3 is a fair fight that IUPAC will address!
 * Well, I see you don't support the arguments I provided for shifting the position of helium. So: what in your opinion makes them different from yours for shifting the position of hydrogen? And whatever happened to your earlier comment in Archive 40:

The position of hydrogen in group 1 is reasonably well settled. Its usual valency is +1. Like lithium, it has a significant covalent chemistry. It can stand in for alkali metals in typical alkali metal structures. It is capable of forming alloy-like hydrides, featuring metallic bonding, with some transition metals. Its anomalous properties can be explained by its electron configuration.
 * How does that interact with your new arguments for hydrogen over boron? Are these still strong arguments in your opinion?
 * It is, in fact, very simple to decide what observations are to be regarded as trivia. How connected are they with everything else in chemistry? And can such arguments be produced for almost any combination of elements? The latter would be a strong argument to consider an observation trivial. You "make an observation and proceed from there to see if other observations, including those made in the literature, are supportive". But do you look for the avalanche of other observations that are not supportive? I add the Wason selection task with its picture straight from its article as an illustration and a question.
 * Thank you for a clarification that excellently explains why I find almost everything you have been posting impossible to accept. Looking forward to the RFC in July where I will propose that we revert to default Sc-Y-Lu. I note incidentally that I already clearly have a very strong consensus here (me, Droog Andrey, Dreigorich, Officer781, against only you on the La side; R8R appears to have declined to participate in the straw poll), and the reason I am still going to do that is that we changed it away from that in an RFC in a first place, and therefore if we change it back, it should go through the same process.
 * Again, thank you for making me think over the past years. But: our gentlemen's disagreement over group 3 seems like it will last. Double sharp (talk) 07:54, 14 June 2020 (UTC)

Further considerations
Double standard(?): Yes, +1 is not the most common o/s for Sc-Y-La, Lu. That said, it’s the context I was interested in. The first thing was Pauling's EN table with B-Al over Sc. EN then increased uniformly down the group. The second thing was that this required La under Y, rather than Lu (EN 1.2). That reminded me of the +1 finding for Sc-Y-La, and not Lu. Then I recalled that +1 was found was found all the way down B-Al-Sc-Y-La (but not Lu). And then H and its +1 popped into my head, and it took off from there, including that +1 is the most common oxidation state for H and Tl. The chain of connections is remarkable.

Your +2 argument is more of a stretch, as I see it.

Unless they say so: Sanderson referred to the similarity of the EN of H (2.1) to that of C (2.5) and on that basis, it was, "placed above the other elements and just to the left of carbon." Pode (1973), as quoted by Cronyn: "It is best placed above and a little to the left of carbon, since it is slightly less electronegative than the latter”. Comparing the EN values, one sees that H is in fact closer to B than C.

+1 becomes more stable as you go down…is not understanding trends at all: I understand the trends quite well. As you go down group 13 the trend is that +1 become more common. Yes, I'm going to put H with +1 on top of B. Same as F is anomalous in being less acidic than Cl. Same as He is more reactive than Ne. Same as Cs is likely more electronegative than Fr.

A silly group like {Na, Be, Pr, Sb, Nb, U}: Yes, I agree, that's really silly. Two s-metals, an f-metal, a p-metal, a d-metal, and an f-metal. Three active metals, a metalloid, a transition metal, and an f-metal, in that order. Bizarre. Stable oxidation states +1, +2, +3, +3, +5, +6. Yes, that's really really silly.

No IUPAC project: Yes, I intend to write up H over B and see if JChemEd will accept it as a follow on to Cronyn's 2003 paper, thus: "The proper place for hydrogen in the periodic table: A redux".

H over Li: Until the light went off I would've continued to support H over Lu as per my older quote. I don't mind He (Z =2) over Be, but I wouldn't support it in a chemical table since, if it got up, H (Z =1) over B, C or F would become yesterday's memories, due to increasing Z no longer being able to be observed.

Unsupportive observations: I look for these as part of the process of sorting through potentially supportive arguments.

RFC: Early, mid- or late July? I’ve received the peer reviews of my group 3 article and I anticipate it will appear online relatively soon, subject to other commitments.

Yes, I’ve learnt all the way through our disagreement, and that is the most important and rewarding aspect. I expect it will come to an end once the IUPAC project makes a recommendation.

Incidentally, I was surprised to learn that Sanderson and two of his peers, in 1940, discovered the first metalloborane in the form of Al(BH4)3. --- Sandbh (talk) 00:52, 16 June 2020 (UTC)


 * How is it a stretch? +2 is equally a consistent context I am interested in. It even makes much more sense because whatever its stability for most elements is, you expect it to become more stable when the filling inner d or f shell becomes hard to get electrons out of (so that only the s electrons are ionised for chemistry), ergo when it is half-filled or fully-filled. Therefore the increased stability of +2 is a nice sign of the end of a d or f block row. And look: Mn2+, Zn2+, Eu2+, Yb2+. Not Gd/Cm and Lu/Lr, but Eu/Am and Yb/No. Now, what exactly is +1 a sign of?


 * There are actual reasons, holistically connected to the rest of the periodic table, why the trend goes slightly sideways for F-Cl and Cs-Fr. The second is just relativistic effects, we know that impacts the whole of the seventh row and in fact the late sixth row as well. As for fluorine vs chlorine, fluorine has lower EA than chlorine just because 2p is tiny (first-row anomaly again), so repulsion is higher. (But for the same reason the EN is much higher once it is already in a bond.) Same reason why the F–F bond is so weak and why F2 is such a ferocious oxidiser. Hydrogen over lithium and helium over beryllium similarly are normal consequences of the first-row anomaly principle. Helium over neon is not, neither is hydrogen over boron. At the end of the day the main reason I cannot support H over B is that hydrogen has the wrong number of valence electrons: it would become the only member of group 3 with zero chance of a +3 state. That's intolerable for me. Same with H over anybody but Li or F (valence vacancies), and even then I prefer Li because I feel that valence electrons are more important than vacancies (or else the spectre of Be-Mg-Zn rises).


 * Yes, that group is absolutely silly. But it satisfies with flying colours the criterion that every member of it forms metallic alloys. So, that's not a terribly strong criterion, is it? Not to mention that you're referring to blocks when you say "Two s-metals, an f-metal, a p-metal, a d-metal, and an f-metal". Well, in that case I have a perfectly simple argument for H-Li and He-Be: anything else either breaks the sequence of atomic numbers or puts an s-element over a p-element. ^_^


 * Well, you know I strongly prefer H over Li. So the fact that He over Be scotches any other placement of H to me is a plus. ^_^


 * As for unsupportive observations: why not state them? I do in fact deal with things that seem inconvenient for my position, either by refuting them or arguing that something more important should beat it (like, you know, how He over Ne looks like the chemically obvious placement, which I argue against). It's also an extremely useful exercise to start searching out points in support of something you think is wrong and seeing how you would deal with them. In an extreme case you may even be convinced to change your mind because of it, like me for He over Be. In fact, you should try it with B-Al-Sc, which many Sc-Y-La arguments end up accidentally supporting. So, you say the "light went off". Exactly what is wrong with those H over Li arguments then, now? ^_^


 * Probably early July in parallel with the hassium FAC. As for IUPAC: if it supports Lu, probably it will stop there; if it supports La, I doubt it. This is because the La arguments tend to be so local that they support B-Al-Sc or Be-Mg-Zn as well if called to arbitrate on them. I would only be convinced if La arguments were presented that don't also end up doing something like that. And one thing I have learnt from this that makes it seem unlikely to me: that there are so many secondary, tertiary, and quaternary relationships among the elements that almost anything can get some arguments behind it. If you show them all your table becomes even more of a mess than Rayner-Canham's (which doesn't even show everything it could). That's why strictly sticking to blocks is the most consistent option, with He-Be and Sc-Y-Lu. Double sharp (talk) 03:16, 16 June 2020 (UTC)

I've just now finished addressing the referees' 29 comments. I re-read our Godzilla thread, and that raised another 28 issues which I've reconsidered and addressed. Tomorrow (Monday) I'll look for any fine details, and typos, and then double check the reference list, and write up responses to the referees' comments for the editor. I expect to be able to submit the final MS later the week.

I started the article on 14 Dec.

On unsupportive observations I've mentioned (1) Scerri (2008, p. 57); (2) Thyssen & Binnemans (2011, p. 80); (3) Stewart (2018a, p. 117); (4) Scerri and Parsons (2018); (5) Tsimmerman and Boyce (2019); (6) Alvarez (2020); (7) Scerri (2020, pp. 392–403); and made reference to (8) group 3 melting points; and (9) electron affinities; and noted that (10) "From a Platonic symmetry perspective and perhaps that of physics, and on some grounds of regularity but not on others, it can be argued that lutetium is better placed under yttrium."

On blocks it's curious to note they first fell out as a result of 19th century chemistry. A table where the blocks are easily seen was created by Mendeleev in 1869. He said this would not be a convenient one. The blocks were subsequently confirmed with the discovery of spectral lines, electrons, and configurations. Yes, there are so many relationships you have to choose which ones to focus on. At the end of the article I say:


 * "…since periodic tables or systems form a continuum-like series of representations, different approaches to the group 3 question (even that used within the IUAPC) will continue to have their uses. And please remember to explain the relevant context to your students. Sandbh (talk) 07:29, 21 June 2020 (UTC)
 * Chemistry is also a continuum. If you don't ask blocks to set everything to rights, Be-Mg-Zn and B-Al-Sc are hard to refute. Double sharp (talk) 09:26, 22 June 2020 (UTC)

GaCl2: Curiously, I see GaCl2 is actually [Ga]+[GaCl4]−; it has Ga in both +1 and +3 oxidation states. So we have: H +1; B +3; Al +3; Ga +3/+1; In +3/+1; Tl +1/+3. Sandbh (talk) 04:41, 24 June 2020 (UTC)
 * For aluminium through nihonium that's indeed a perfect trend, each element has a more stable +1 state than the previous, and +3's domination lowers until +1 wins at thallium. Boron also makes sense as the nonmetal that starts it: mostly +3, but of course you may easily get +2, +1, −1, that's not too different from carbon. How exactly does hydrogen fit into that with only +1 and −1 and no chance of anything higher or lower? Double sharp (talk) 09:12, 24 June 2020 (UTC)

Useful reading
Luchinskii, G.P., Trifonov, D.N.: Some problems of chemical elements classification and the structure of the periodic system. In: ''Uchenie o periodichnosti. Istoriya i sovremennoct’''. Nauka, Moscow pp 200–220 (1981) (in Russian): They discuss four positions proposed for H, i.e. above Li, B, C or F. I've requested a copy.

H-Li and He-Be
For me, Henry Bent's argument is decisive.

[Helium over neon b]reaks twice-over the Rule of First-Element Distinctiveness: Groups’ first-elements are particularly distinctive with respect to their congeners, with distinctiveness increasing, block-to-block, in the Jensen order s >> p > d > f. With He above Ne, the rule does not hold for He, nor does it hold for Be of the s-block more so than for first-elements of the p-block. With He above Be, the rule and the Jensen order holds for all first-row elements.

Does science want to live forever with these inconsistencies in its iconic representation of chemistry?

The Rule of First-Element Distinctiveness has two dimensions to it: vertical and horizontal. The vertical dimension is a block-to-block trend in distinctiveness of first-row elements with respect to their congeners. The horizontal dimension is a block-to-block trend in distinctiveness of first-row elements with respect to their first-row neighbors. He/Ne destroys both of those trans-table trends. [Same story if you try to wrest hydrogen away from lithium on the grounds of making its placement look more homogeneous.]

...

The downward nonmetal-to-metal transition is particularly pronounced, at the outset, in the s-block, for H above Li and He above Be. That onset is less pronounced in the p-block, and still less so in the d- and [f]-blocks, where all elements are metals. The phenomenon exhibits a Jensen-like block-to-block trend, increasing in the order: s >> p > d > f. Therein is another trans-table trend contingent on location of helium above beryllium.

In summary: helium’s location in periodic tables is a big deal. Above beryllium, helium stands out as the Periodic System’s most distinctive element. (Above neon helium does not stand out as a distinctive element.) Above beryllium, helium anchors a number of previously unrecognized regularities in the Periodic System. Helium-above-neon conceals the new regularities.

Just as B-Al, C-Si, N-P, O-S, F-Cl, Ne-Ar display irregularities but are placed according to their number of valence electrons; and just as the first-row f elements are less distinctive from the heavier ones than the first-row d elements are from the heavier ones than the first-row p elements are from the heavier ones, we should be listening to the 2p vs 3p trend and make sure hydrogen and helium are placed over elements that match them in the number of valence electrons, without regard to other differences. Those differences are expected and regular. They always involve the biggest drops in electronegativity and the biggest jump in the stability of higher oxidation states. Helium 0 (+2 should be well unstable) over beryllium +2 is completely reasonable here, the added stability of lithium +1 over hydrogen +1 another example. Above neon, helium is simply badly placed: helium is less electronegative than neon, the biggest dip in ionisation potentials is Ne-Ar (the first-row anomaly motif) and not He-Be. Same problem with hydrogen over fluorine.

Hydrogen over anything else is even worse: you get unwanted homogeneity putting hydrogen over boron and carbon in electronegativity and a chemically unprecedented destruction of the principle that elements in a group have the same number of valence electrons. This when we have the precedent of boron through neon showing that we should be respecting the number of valence electrons above all, and that we should expect hydrogen and helium in 1s, the only time when you have incomplete shielding effects and a kainosymmetric orbital without radial nodes combined, to be the most distinctive elements compared to their groups in the entire periodic system.

Hydrogen over lithium and helium over beryllium is demanded by the regularities of block filling. Double sharp (talk) 12:31, 19 June 2020 (UTC)


 * Here's what Bent said in his book:


 * He starts with the observation that there are no construction conventions for going from Mendeleev’s line to a periodic table (p. 3).


 * He suggests four such conventions:
 * Elements of each group in vertical columns;
 * Z increases from left to right, and top-down;
 * No gaps; and
 * Maximum regularity in column and period lengths.


 * From there he says the LSPT is the outcome (p. 3).


 * In the rest of the book he examines: the case for HeBe; and the regularities of the LSTP, including those based on numerology—as he refers to it (pp. 34, 119, 125, 186). Some of these regularities are rather esoteric e.g. “Ratios of heats of vaporization of the last two elements of blocks’ first rows.” (p. 155)


 * Perhaps the nicest thing he likes about the LSPT is that it well illustrates the law of first row distinctiveness i.e. s (as HHe) >> p > d > f. This can be seen in the conventional form too.


 * He repeatedly observes there is no “best” periodic table (pp. 108, 127, 151, 140, 170, 175, 183, 191). Using more than one table is a step to perfection (p. 119). Use whichever table is best suited for the task at hand (pp. 151, 158).


 * On regularity, he quotes an unidentified physicist as saying, “In physics, violations of symmetry are viewed as more beautiful than perfect symmetry (as is the case for ‘beauty marks’ on a woman’s face and asymmetries in art and in nature all around us) …If there were just one perfect PT, chemistry might be pretty boring.” (pp. 111–112).


 * Bent later quotes Feynman: “Some think that the true explanation of the neat symmetry of nature is this: that God made the laws only nearly symmetrical so that we should not be jealous of His perfection.” Bent goes on to say, “Others think that the true explanation for the need for more than one periodic table is this: that God made the initial conditions for the Big Bang such that the evolution of the universe would lead to many-electrons and a wacky s-block, in order that chemists and physicists would not be bored.” (p. 140)


 * Bent acknowledges that He does not always need to go over Be (p. 112).


 * He lists the positives and negatives of the conventional form, and the LSPT (p. 143).


 * According to him, the LSPT and the conventional table complement one another (p. 164).


 * If you look at the cover of his book, you'll see that La under Y is more regular. Rearrange his table into the traditional form. Note how group 3 goes black-black-white-white, and that the f-block starts as black-black. Now wipe out the black-black at the start of the f-block. Change group 3 so that it goes black-black-black-black. Add two white boxes onto the end of the f-block. Group 3 becomes regular; the f-block is grey-grey, matching group 4. Bent was a closet La supporter! Sandbh (talk) 08:05, 21 June 2020 (UTC)
 * For clarification, just because I think Bent has it right on the helium issue does not mean I agree with him on everything. I do not even agree with all of his arguments for helium over beryllium, just the ones I quoted. And I do not even agree with the idea that the LSPT is the ideal table: the "period divide" is too salient. When I quote him here I simply mean "here is an argument by him that I agree with". ^_^
 * s >> p > d > f is less clear in the traditional form because of helium over neon. It makes hydrogen look like a lone weirdo instead of being part of this trend.
 * Perhaps there is not a perfect PT. However, I believe there is one that is most useful for general purposes. In my opinion the importance of blocks and the regularity they bring is very high and is a strong argument in favour of He-Be and Sc-Y-Lu-Lr. Moreover, we can very well understand that helium is a noble gas even if we place it elsewhere (just like we understand that hydrogen is not an alkali metal).
 * And there is not even that good an excuse for Sc-Y-La-Ac because lanthanum and actinium are much more similar in their behaviour to f-elements than d-elements in every way. It doesn't even have the chemically good excuse putting helium over neon has. Double sharp (talk) 08:38, 21 June 2020 (UTC)

Introduction into superheavy elements
Hello everyone,

you may have seen the new Hassium section, which serves as an introduction into the basic concepts about synthesis of superheavy elements. In a discussion with Double sharp, both he and I agreed the introduction is best kept brief and a more extensive introduction should be put into the main superheavy element article (see Superheavy_element). The idea is that the reader does actually get some understanding before getting to read the whole article while a more extensive discussion is slightly off the topic of the individual element, and should be kept with the general concept. The reader can reader a brief introduction, get interested, and read the full version in the appropriate place; if only a link is provide, the reader is not nearly as likely to click it.

The brief introduction for hassium could be of great use for all superheavy element articles, but the question then arises: how do we keep the brief introduction up to date in all at least fifteen articles? It seems that the appropriate solution would be transcluding that bit into all articles on individual superheavy elements, but from where if superheavy element is to have the longer version? I'd very much like to hear comments from you on this. Possibly someone wants to make a more general comment on the topic of the introduction into superheavy elements in general, in which case I'm all ears.

Pinging please see the question and leave a comment. Sorry if I forgot to ping anyone.--R8R (talk) 10:22, 16 March 2020 (UTC)


 * Agree. Droog Andrey (talk) 10:41, 16 March 2020 (UTC)
 * Great to hear that. Do you have any idea on where the transcluded section should be stored? I have so far considered transuranium element or leaving it in hassium and transcluding the section from there. I don't like the second option, but it's an option nonetheless.--R8R (talk) 14:05, 16 March 2020 (UTC)
 * I think Superheavy_element is the best choice. Droog Andrey (talk) 15:04, 16 March 2020 (UTC)
 * That is for sure, that's where the longer proper introduction will be. What I'm looking for is the place for the shorter introduction that is supposed to interest the reader enough so that they read the longer introduction at Superheavy element.--R8R (talk) 15:33, 16 March 2020 (UTC)
 * I feel that the introduction should definitely be focused on the element itself instead of its synthesis. A brief mention might be okay, but really, it should go in the History or Discovery section. For an introduction, I would propose sticking to the known properties of the element - keep it simple for the non-technical readers.  ― Дрейгорич / Dreigorich  Talk  14:59, 16 March 2020 (UTC)
 * The aspects of synthesis described should be pertinent to each element. I believe a short introduction like the one in hassium is helpful to give context, but I would not recommend transcluding it (the short section) because not everything relevant to hassium may be relevant to every other SHE, and we don't want any articles straying too far off topic. We need to make (likely minor) adaptations on a case-by-case basis, with the aggregate, detailed description in Superheavy element. ComplexRational (talk) 16:04, 16 March 2020 (UTC)
 * Re you see, synthesis is absolutely crucial to every superheavy element (SHE), much more so than to a stable element. There are two major differences: one is that you can only produce SHEs in ridiculously small quantities compared to the stable elements, which makes understanding how the minuscule amount you get at all so important. The other thing is that SHEs don't live very long, they are created, they last for a short while so that you, if you're lucky, run an experiment or two with it, and then they're gone. And even as for those chemistry experiments, every chemistry experiment starts as a nuclear physics experiment. So that's why creation is such a big part of the whole topic of the superheavy elements, and that's why we need to introduce it. I share your idea that article should be kept as simple as possible---but not simpler than that, or we interfere with the idea of writing an encyclopedia otherwise---and the non-technical readers are aided by a brief explanation of how things work and an incentive to read a larger description in a different article.
 * Re please go ahead and look at the shorter introduction scrupulously. What, if any, modification would it possibly need for any other SHE article?--R8R (talk) 20:05, 16 March 2020 (UTC)
 * As it stands, any changes would be minor, since the same technique is generally used from Rf onwards and other techniques have not yet yielded any new SHEs, and decay properties are generally consistent (though SF branches aren't significant in the heaviest elements, but even this will likely change as more isotopes are synthesized). I'd say this current version is a pretty solid baseline. ComplexRational (talk) 20:45, 16 March 2020 (UTC)
 * The point that I'm trying to get to is that there is not going to be any change at all. Nothing in the short (or long) introduction is specific to hassium or any element; it merely explains the basic principles. Can be reused in a different SHE article very easily. I'm certain about that and I welcome you to challenge this assumption if you disagree.--R8R (talk) 20:49, 16 March 2020 (UTC)
 * Yep. The question is how much is too much? Too little? It should be enough to be understandable that there's not much known about it, but not so much that it clogs up the introduction. Some For some elements with little known, it will be more critical than others. Not much is known about either astatine or francium, but a synthesis section for either one makes little sense - stay to what chemical properties are known. For something like hassium, it would be more critical, as there's really almost nothing to go off of except some guesses.  ― Дрейгорич / Dreigorich  Talk  20:20, 16 March 2020 (UTC)
 * I thought you were talking about the lead at first... :-/. Dumb me. The method I'd argue could be something like an introduction and a link to Superheavy element for more info, like Main article: Superheavy element.  ― Дрейгорич / Dreigorich  Talk  20:23, 16 March 2020 (UTC)
 * That is precisely what is done at Hassium.--R8R (talk) 20:38, 16 March 2020 (UTC)
 * I think then that would be a great introduction, though I wonder if it's needed on 15-20+ articles. Surely it would get too repetitive after a while?  ― Дрейгорич / Dreigorich  Talk  22:26, 16 March 2020 (UTC)
 * This is what I was getting at as well. The content is great, but I'm a little hesitant to include verbatim copies of this section in so many articles. In several of my GA reviews (for E124 and E126), this was explicitly not recommended; I had to do a little wordsmithing and tie it back into the article's main topic (but in the case of Hs, this latter point is less necessary). ComplexRational (talk) 01:02, 17 March 2020 (UTC)
 * Aha, I get it. This is a reasonable concern. I have considered it myself. I don’t think, however, that the proposed solution makes the problem too bad. Consider this: suppose you wanted to read the article on darmstadtium. It does not have that introduction, and you would never guess that you could find one in hassium. The introduction is helpful for hassium and it would be equally helpful for darmstadtium if the article on the latter had it. But it’s not there, and there is no hint there is one at hassium.
 * This is not to say, however, that I dismiss your problem: the section was originally much longer (see the current long introduction). While too much repetition might not seem very appealing, much of that repetition has already cut out and is kept in one place (in Superheavy element). I think it is a great improvement over keeping the long section in an article on an individual element.
 * I did once have your line of thinking myself, so I certainly understand the legitimacy of the concern here. However, it is also important that we are not writing a book where we may need the text not to be too repetitive between chapters (or in our case, articles); we write first and foremost an encyclopedia, and it is important that if some useful bit is added in one article that all other articles also get it, hence the need for transclusion. If I were facing such a problem at a GAN, I would say that to the reviewer.—R8R (talk) 12:14, 17 March 2020 (UTC)
 * I think just a link under "Introduction" is sufficient. Repeating one and the same section in 15 articles seems silly. But if you want to do it, you can make the introduction a Wikipedia template. Burzuchius (talk) 14:08, 17 March 2020 (UTC)

I conclude from the above that there is no strong objection to the proposal, and I've been WP:BOLD to advance the introduction to the four present-day FAs: two of them written by myself (tennessine, dubnium) and two by other editors (oganesson, nihonium). I think the introduction looks great in every one of these four. If there are no objections, I'll add it to all elements from 104 onward.--R8R (talk) 22:36, 27 March 2020 (UTC)
 * It looks great to me, so I think there is no problem in putting it in all elements from 104 onwards (maybe even 102 onwards, since No and Lr were discovered by hot fusion with light ions just like Rf, Db, and Sg). Double sharp (talk) 06:57, 28 March 2020 (UTC)


 * I agree with Дрейгорич / Dreigorich  re, "I feel that the introduction should definitely be focused on the element itself instead of its synthesis. A brief mention might be okay, but really, it should go in the History or Discovery section. For an introduction, I would propose sticking to the known properties of the element - keep it simple for the non-technical readers."
 * I don't support a transclusion into each article, nor a template.
 * I had a similar problem with the Metalloid FA. I solved it by putting a blurb at the start of the relevant sections and before the text e.g.:


 * The focus of this section is on the recognised metalloids. Elements less often recognised as metalloids are ordinarily classified as either metals or nonmetals; some of these are included here for comparative purposes.


 * See here and here.


 * Just after the start of each introduction you could put a blurb like this:


 * ''For an introduction to the basic concepts of the synthesis of superheavy elements see Superheavy element/Short introduction


 * That's all that's needed. Sandbh (talk) 03:38, 6 April 2020 (UTC)

I have for the time being been bold and put the short introduction into the articles on elements from 104 to 118. I closely considered the idea of not doing that, and I decided to go ahead anyway. The introduction itself is applicable not only to the topic of superheavy elements in general, but also to each individual element. The big notable thing about superheavy elements is that synthesis is of paramount importance for the latter; no topic of a regular element can claim the same with possible exceptions of hydrogen and helium, or uranium and plutonium (and I am still inclined to say not in either case). To quote Christoph Düllmann, a very big name in the area, "Every chemistry experiment starts as a nuclear physics experiment." The topic would not have even been to begin with if it weren't for synthesis and nuclear reactions. This is unlike the case of stable elements, where you could do chemistry of even fluorine long before you could synthesize fluorine gas. This is also why every article on a superheavy elements starts with a section of history of discovery, not one of its properties.

I promise to think some more on the topic, but for now, I am satisfied with this thinking. Whether the same should be done for elements 102 and 103 as well as 119+ is up for deliberation.--R8R (talk) 13:37, 11 April 2020 (UTC)
 * For 102 and 103, we might have to mention a few different techniques in relation to the history and discovery; they were discovered in light-ion bombardment before cold and hot fusion really were studied. But it might be doable with some small tweaks, and there would be a pretty clear benefit for readers. And for 119+, I'd say for now to use an abridged version at most because they are of course undiscovered, and we don't even know if new techniques will be required to synthesize further isotopes; I'd hold off on those a bit longer, but I'm open to further ideas. ComplexRational (talk) 16:24, 11 April 2020 (UTC)
 * The former is also true of 104-106, though. Double sharp (talk) 17:06, 11 April 2020 (UTC)
 * I thought that was precisely hot fusion?--R8R (talk) 17:48, 11 April 2020 (UTC)
 * Well, that will teach me not to write late in my time zone. ;) Yes, it is hot fusion. But my point rather stands; there is not really a difference between how 102 and 103 were synthesised, from how 104, 105, and 106 were synthesised. Double sharp (talk) 03:16, 12 April 2020 (UTC)
 * okay, let's say we want to have that intro there, too. Then the question comes, how do we adapt it? The big difference I see is that it is generally agreed that the set of superheavy elements starts with Z = 104, and the intro starts with the words "A superheavy atomic nucleus is created in a nuclear reaction that combines two other nuclei of unequal size into one," and the transclusion tag also points that it is transcluded from a SHE article, which is potentially confusing.--R8R (talk) 12:04, 12 April 2020 (UTC)
 * Since 102 and 103 usually are not labeled "superheavy elements", transcluding the introduction would not be ideal and violate the "usual" definition given in superheavy element. We certainly could do a manual copy-and-paste of the relevant synthesis bit, perhaps also noting how neutron capture and alpha irradiation were judged to be insufficient and introducing the technique of light-ion bombardment (as 102 and 103 were the first discovered elements pioneering this technique). Some of the history is applicable, but all the description on terminology and decay modes is not (for example, EC is still a major decay mode here, while it is rare or only theorized for heavier elements, and SF plays a larger role here as the island of stability is nowhere near these nuclides). ComplexRational (talk) 16:26, 12 April 2020 (UTC)
 * The decay mode consideration is a good one, thank you. That didn't cross my mind.
 * If there is going to be variation of the text, we need to establish over which axes would those variations go (decay modes with inclusion or non-inclusion of the island of stability, anything else?) and how far do we want to go back (do we want to include, say, californium?)
 * On a brief inspection of the relevant infoboxes, I don't see too much electron capture in the most important isotopes of nobelium and lawrencium. Should we bother in the brief introduction with it at all?--R8R (talk) 18:53, 12 April 2020 (UTC)
 * Since No and Lr are not usually considered "superheavy", I would propose that the wording be mostly retained, but edited to simply talk about the heaviest elements on the table instead (so it would be a manual copy-paste, adding some text about how the neutron capture up to Fm and the alpha irradiation that worked for Md would come up dry here – it's fairly obvious why, because of the 258Fm wall and the fact that you can't get a target beyond Es). We can add a mention of electron capture to the decay mode. Double sharp (talk) 13:07, 14 April 2020 (UTC)

don't archive until the issue with elements 102 and 103 has been resolved--R8R (talk) 11:58, 6 June 2020 (UTC)
 * I guess I will say here that I think this issue could be easily resolved by simply copy-pasting in something similar to but not exactly the same as the template for them. Double sharp (talk) 12:24, 6 June 2020 (UTC)
 * I think so too, yes, but somebody (probably me) needs to adapt the text for those articles and add it there. Or we could do it in a joint effort. Anyway, the issue won't be resolved until we've done that.--R8R (talk) 12:35, 6 June 2020 (UTC)

please take a look at Nobelium. Is it good enough or did I miss anything? Could we potentially replace all instances of transclusion of Introduction to superheavy elements with this?--R8R (talk) 19:31, 12 June 2020 (UTC)
 * I'm a little confused. In terms of content, it covers everything important about the basic formation and properties of superheavy elements. But I don't understand what you mean by "replace all instances of transclusion" – do you mean make this the new transcluded text or manually copy-and-paste? In the former case, I'm curious why you're using nobelium as a base case since it isn't usually considered a superheavy element, and in the latter, it would defeat the purpose of transclusion and simply be a case of ~15 repeats. Could you please elaborate on your suggestion? ComplexRational (talk) 22:44, 12 June 2020 (UTC)
 * Gladly. You see, I have created a new section for elements 102 and 103 at Introduction to the heaviest elements; it is a mere modification of the existing Introduction to superheavy elements used for elements 104 through 118. Nobelium is merely a showcase of using that section. The new section for elements 102 and 103 could be used for articles on superheavy elements, and it would be great to centralize content. At least it seems to me that it could; please see the new section and see if I’m correct.—R8R (talk) 07:13, 13 June 2020 (UTC)

It appears there haven't been any objections and I have thus changed all articles to transclusion from Introduction to the heaviest elements.--R8R (talk) 12:06, 26 June 2020 (UTC)

Use a template?

 * re the "from where [to transclude the short introduction]": simple, if we want to do this, a template is the best place. I see no reason to transclude it from, say, hassium. Template is where we editors can keep it stable easily. (I thought is was ill advised at Wikipedia (considered bad practice) to transclude body text anyway, but I cannot find that statement anywehere so it must be absent). A more detailed puzzle might be how to make the block of text nicely flow in each article's flow. It might attach subtle strings (requirements re good writing). -DePiep (talk) 07:14, 18 March 2020 (UTC)
 * I strongly disagree with putting the introduction into a template. I feel about this very strongly and I will try to explain why. The very concept of Wikipedia revolves around the idea that it is easy to edit for anyone. You need no knowledge of anything; just follow the markup and you'll be good. This was further improved when visual editing came to being. Now, of course, there are some limitations. It is advisable to conceal some complicated templates from the public, so that the markup is not stored in the article text and does not confuse anyone, and the thing is easier to edit (including those who understand well how the markup works). Some topics are too tempting for people to ruin them (like Donald Trump, Muhammad, Jews, whatever it is that gets people to lose their minds), so some limitations are in place. Here, however, we are talking about uncontroversial encyclopedic content, rather than a supplement to that. It would be a very bad idea to make it difficult to edit and this would contradict the very principle of Wikipedia without giving anything in return (like protection from vandalism) that could compensate for that. It is already bad enough that it needs to be stored in one place for consistency, but at least clear guidance where to go to can be given (see the first section of NATO bombing of Yugoslavia for an example).
 * I generally see why you wouldn't want to transclude that from hassium; that's where the question about where the section would actually be stored comes from. I'd be eager to listen to suggestions on that as long as it's not a template.
 * To be perfectly clear, templates are fine but they are not used to store encyclopedic content (as opposed to anything that supplements it) in them.--R8R (talk) 21:26, 18 March 2020 (UTC)
 * You could still make a template and subst: it instead, or even introduce it from hassium to the other articles using subst:. That way, no encyclopedic content is stored remotely (each article/section can still individually be edited), and major changes can be easily transferred with a semi-automated run of 15 subst:s. ComplexRational (talk) 21:45, 18 March 2020 (UTC)
 * User:ComplexRational: subst: is the oppposite ofwhat is proposed here. It actually fixes the transcluded text into today's version; later edits (to the source text, think the Hassium section), those edits are not appearing in other articles. -DePiep (talk) 07:05, 19 March 2020 (UTC)
 * I am well aware of that and how subst: works. I only proposed it because this thread seems intent on establishing a standard introduction, while I stand by my point of keeping it open to minor adjustments in each article–so there is no need for centralized editing, room for changes specific to each element if necessary, and reviewers or scrutineers do not get annoyed with the repetition of text in 15 articles. Subst: would be a one-off establishment with these provisions. But of course, if transclusion is preferred, I will not object to a template, subpage, or whatever the preferred practice is for article text. ComplexRational (talk) 19:23, 19 March 2020 (UTC)
 * Last buttons first: "templates are fine but they are not used to store encyclopedic content" (source? I could not find this): Yes they are, for exactly the reason you raise in this question: repetition of information (here).
 * In short, once you want to transclude text, template cannot be discarded beforehand.
 * Now on the ease of editing. My solution is, while putting the text block in a template: in top, add a link like This section:. In Wikipedia, this is commonly accepted (also for encyclopedic text too).
 * -DePiep (talk) 07:29, 19 March 2020 (UTC)

Technical implementation
I've been looking on how to implement this technically (transclude the section from Hassium).


 * Route One. Basically: when not a template, add the namespace to the page name in the  notation (when page is not in the Template: namespace). So write in the target page:   Articles just get a colon


 * Then, in the source article (Hassium) add these tags to select parts to be transcluded:

Lede of hassium text here &lt;onlyinclude>==Intoducton== A superheavy ... images, refs, &tc. ... have been made.&lt;/onlyinclude> Rest of Hassium text here


 * This is examplified in Transclusion, third example: article sectionJoseph Gordon-Levitt imports the lede of article HitRecord.


 * Other Route. As the very same section in WP:Transclusion says in its intro: "When two pages need to discuss the same material in the same way, they can share a section. This involves creating a third page and transcluding that page onto both pages". I note it says "page", in an unspecified/any namespace; I take "discussion" more widely, to include article body text.


 * So this third page could be a template. Adding a well-crafted v-t-e links would solve editability.


 * Importantly, I claim that this is way more easy to grasp for editors than the ; plus the extra presciptive comment in that hassium section. We all know how bad such instructions are read or understood, if at all.


 * My conclusion. While writing this, I came to think of this technical solution, in case we do want that central section:
 * The Introduction section content is in page Superheavy element/Short introduction. Part of mainspace, and quite a logic title without the why-in-Hassium?-distraction. Of course it has some v-t-e box.
 * To me, this is equally sound as using a template. I reject the in-hassium-article construction. -DePiep (talk) 08:08, 19 March 2020 (UTC)
 * I did not realize a subpage was a feasible solution. We could do that; seems like a great to me since that's allowed. Thank you for bringing that up.
 * Some readers who could edit a main space page would be afraid to edit a template page. As far as we can stay in the main space, that's good.--R8R (talk) 10:19, 19 March 2020 (UTC)
 * Trivial note: actually, in mainspace this is not considered a "subpage"; it is considered a stand-alone article (example: AC/DC). Probably, such a page could have &lt;onlyinclude> tags to allow extra info (or even make formally into a full stand-alone article). Some wiki-purists might frown upon this, but we may have good arguments to do so. -DePiep (talk) 10:59, 19 March 2020 (UTC)


 * Currently: an editor has moved the article content into template Superheavy element introduction . Workings is the same. I see no need or gain in fighting this choice, but that's just me.
 * On a sidenote, for inspiration: an introductionary article, esp into difficult topics like SHE or QM, is well received. In March I was involved in "getting some, any, corona-related FA article speedily as TFA". Guess what: on March 27, the article Introduction(!) to viruses was at MainPage and got >100k hits (3x24h). Also, reading the article made me into a virologist, which is nice to be these days. Next stop for me: QM-specialist. -DePiep (talk) 00:39, 2 April 2020 (UTC)


 * FFS,, stop messing around. The Template is Great. -DePiep (talk) 19:06, 4 April 2020 (UTC)
 * Please strike this. And why is the template great? ComplexRational (talk) 21:20, 4 April 2020 (UTC)
 * OK then The table is great, by aim & setup. -DePiep (talk) 21:32, 4 April 2020 (UTC)

I'm rather surprised that a clarification is needed, but since it is, I'm happy to explain my reasoning.

First of all, the rules consider having the common section as a separate page as a fine possibility. To quote Transclusion,
 * When two pages need to discuss the same material in the same way, they can share a section. This involves creating a third page and transcluding that page onto both pages. This third page may be a page in its own right or a subpage of either of the other two, and if the first it may be placed in the same namespace as the other pages or in template namespace.

What I'm opting for is a third page in the same namespace as the other pages. That's one of the possibilities outlined in the relevant technical page. It is, I note, not a guideline, so if you can find a guideline that says otherwise, maybe you can correct me. However, I want a guideline before making such a statement. "R8R, ffs what are you doing, template is fine" is no explanation. I can't respond to it; there is nothing to say to, "that's good reasoning, I stand corrected" or "that's not good reasoning, here's why." There is no reasoning at all.

Second, this guideline has been brought up already, in this very section. When I moved the section where I did, it didn't cause any controversy back then. Where this is coming from is genuinely puzzling to me, given that I'm merely moving it to the original location. I did announce where it would go; nobody protested.

Third, I find it very important so I will reiterate: editing Wikipedia should be as easy for an editor as possible. A small "edit" link does not explain why the usual "edit" link in the header of the section does not work; it is more puzzling. The template I added explains that the text is stored elsewhere. I hope that you will undo this edit of yours.

Fourth, I have already said this too, but I will be happy to reiterate: the text contains encyclopedic text as opposed to anything that compliments it, and encyclopedic text should be stored in the main space. The very fact there is that green space below (template documentation) was unsettling to me when I was learning Wikipedia and the markup. Only later did I learn how to work with it. This is not what most readers should be able to do, they should not feel disenfranchised by ending up in a "technical" zone. To add to that, Template namespace, which is a guideline, says, "Templates should not normally be used to store article text, as this makes it more difficult to edit the content. They should also not be used to "collapse" or "hide" content from the reader." We are clearly talking about article text here; why should we not store it in the main space?

Fifth, by moving the page back to its original title, I undid the moving, that's when discussion begins. I actually tried to start it even earlier, here, but my call for discussion was not returned. This point is merely for making clear what the actual order of events was and what is the "revert" in the BRD scheme.--R8R (talk) 22:57, 4 April 2020 (UTC)

Edits
Not about the concept of centralising this text. But about (future) edits, as in regular article improvements.
 * As it stands in Hassium now, it needs adjustments into the article text flow. For example, a section title "Introduction" can only pertain to "Hassium". Instead, the section better be like "Introduction of superheavy elements". -DePiep (talk) 15:07, 29 March 2020 (UTC)
 * What do you mean by article text flow? Is this similar to what I described above about slight differences and adjustments for each SHE? I'm not opposed to a section title change if that's all this is about, though. ComplexRational (talk) 16:04, 29 March 2020 (UTC)
 * Yes, it is the same. I'm not sure if your proposal (tailored adjustments per element) can be achieved. When simple, we could start using parameters... But varying sentences? Re this, I am not too familiar with the topic to propose content edits. Anyway, my "article text flow" here is about connections between sections. At first reading, I saw the same isolation in section Hassium (no hassium-specific text in there either). -DePiep (talk) 16:14, 29 March 2020 (UTC)
 * Shorter: think what is best in the TOC: "Introduction" or "Introduction of superheavy elements" (or "The creation of SH elements")? -DePiep (talk) 16:17, 29 March 2020 (UTC)
 * Alright, that makes sense. Given the nature of the content, I'm inclined to think "introduction to superheavy elements" or similar is more appropriate so readers are not misled into believing that each element has an "introduction". Finer content changes (varying sentences) don't seem necessary at the moment; we'll discuss the technical nature of that if and when it is necessary (e.g. I think when 119 and 120 are discovered, and even more so beyond that, a few small changes might be in order). ComplexRational (talk) 16:23, 29 March 2020 (UTC)

Abbreviations
It occurred to me that the short introduction (originally based on what was written in hassium) that is transcluded into 15 articles uses some acronyms of the discoverer facilities that are introduced in hassium but may not be introduced elsewhere ("JINR" is introduced in most but not all articles, "LBL" is used in some but easily not all, and "RL" may be even unique to hassium). It сould seem sensible not to use those acronyms then and simply spell out the names of the facilities in the notes, but notes are generally actually supposed to be rather short and dense in terms of content (I think) and if those facilities are referred to by their acronyms in main article texts, it would be strange not to do the same in notes. So I'd like to hear more opinions on this. What do you think? pinging everyone I've seen in this section barring Dreigorich.--R8R (talk) 12:20, 6 June 2020 (UTC)


 * "not to [?] them", a word missing? -DePiep (talk) 14:29, 6 June 2020 (UTC)
 * indeed, thank you very much for bringing my attention to it. Corrected my phrasing in the original post.--R8R (talk) 14:36, 6 June 2020 (UTC)


 * It appears that even in hassium, some of the acronyms in the introduction occur before they are spelled out in a later section. I'd expect that this is the case for other articles as well, where the laboratory may not be mentioned in the infobox or lead. That said, I think it's most prudent to introduce them in the notes of the short introduction; any redundancies would be less widespread than undefined acronyms. Alternatively, I could even try to rework some of the notes to eliminate the need to include these acronyms, in which case we also make the notes perhaps less unwieldy while solving the problem of inconsistencies resulting from transclusions. ComplexRational (talk) 16:29, 6 June 2020 (UTC)
 * the thinking in hassium is that all notes are really in the Notes section, which comes after all acronyms have been introduced. I don't know if there are any specific editorial guidelines on this we could follow. Introducing acronyms in notes, however, doesn't seem right as notes are supposed to be merely an addition to the main bulk of the content, which I believe takes precedence.--R8R (talk) 21:49, 6 June 2020 (UTC)


 * My take: First setup best be as if the transcluded section does not matter. So: acronyms spelled out at 1st appearance in the body (incl infobox). A second spelling out, is later sections, is acceptable (to support reading only the latter section). Then, additionally, they can be spelled out in the Notes section too (1st appearance there). In general, such redundancy is acceptable. Next step: check how this turns out in other articles with the transclusion; i.e., which acronym would fail the first-mentioning principle. (Logic: Since they do not appear in the transcluded section body text itself, there can be no fault re this; don't know yet for other Notes in an article).
 * Recap: spell out at (1) first appearance in body, and (2) first appearance in the Notes. This redundancy is acceptable (spelling out is required, and 2nd spelling out is not forbidden). Would this solve the question? -DePiep (talk) 12:45, 7 June 2020 (UTC)

The PT and the physics that drives it
[https://www.nature.com/articles/s41570-020-0195-y#:~:text=The%20periodic%20table%20can%20be,according%20to%20their%20intrinsic%20properties.&text=This%20order%20enables%20us%20to,and%20physical%20properties%20of%20elements. Here.] By Schwerdtfeger, Smits & Pyykkö (2020).

Some passages of interest:


 * "The periodic table can be seen as parallel to the Standard Model in particle physics, in which the elementary particles known today can be ordered according to their intrinsic properties. The underlying fundamental theory to describe the interactions between particles comes from quantum theory or, more specifically, from quantum field theory and its inherent symmetries."


 * "…the important Aufbau principle introduced by Bohr and Pauli that, together with Hund’s rule, is considered as the second building block of the PTE, after the atomic-number ordering. Chemical behaviour is the third most important criterion that guides the order of elements in the PTE and an essential tool for all chemists."

That's interesting. So the three building blocks are held to be: [1] Z ordering; [2] Aufbau principle + Hund’s rule; [3] chemical behaviour.


 * "Despite the huge success of the Madelung–Janet rule, the most appropriate definition of the start and end points of the lanthanide and actinide series remains a matter of dispute. Inserting the lanthanides La–Yb and actinides Ac–No between groups 2 and 3, and Lu [4f145d16s2] and Lr [5f147p17s2] (note the difference in the occupation of p and d levels between the two elements) into group 3 fulfils the Madelung– Janet rule and results in a more natural placement of these elements into the PTE. However, placing La [5d16s2] and Ac [6d17s2] into group 3 and the series Ce–Lu and Th–Lr afterwards has the advantage of keeping La and Ac as the first elements of the lanthanide and actinide series to which they give their names. In a set of molecules, Xu and Pyykkö found that Lu and Lr behave in a very similar way. Moreover, the placement of the 4f-to-6f and the 5g elements in Fig. 1c keeps the group number, G, equal to the number of valence electrons. We are not delving further into discussions of chemical similarities between the two different definitions of the group 3 elements, as there are many different opinions on this. The International Union of Pure and Applied Chemistry (IUPAC) conveniently avoids this controversy by leaving the two positions in periods 6 and 7 of group 3 empty and listing 15 instead of 14 elements for the lanthanides and actinides, thus counting from f 0 to f 14.


 * "1s elements. We start our discussion by mentioning the two most abundant elements in our universe, H and He, synthesized directly in the primordial nucleosynthesis roughly 10 seconds to 20 minutes after the Big Bang. These are placed into groups 1 and 18, respectively, although their chemical and physical behaviour is quite distinct compared with their heavier homologues in the PTE."

With regard to hydrogen I suggest its distinctiveness compared to the alkali metals is over-emphasised.


 * "He fits rather into group 18 than into group 2 of the PTE, although we note the existence of gas-phase cations, such as HeH+, or metal helides, such as VHe3+, YHe3+ or AlHe3+ (refs 53–55), and the observed high-pressure electride compound Na2He. This is a prime example in which chemical similarity wins over electron configuration."


 * "Although H and He clearly separate from the rest of the PTE, almost every chemist agrees that we can leave these elements in their current place in the PTE, keeping their distinctive quantum nature in mind."


 * "HgF4 has been identified not too long ago by Wang et al."

As we know, experiments conducted in 2008 could not replicate HgF4. That said, it has been predicted to be stable at high pressure, within the range of 30 to 40 GPa, or so.


 * "Stability of superheavy elements The heaviest naturally occurring elements of the PTE on our planet are U and trace amounts of 244Pu found in the deep sea floor. In fact, until 1943, only the elements up to Pu, which was produced by a deuteron bombardment of 238-U by Seaborg and colleages, were known (Fig. 1b). At that time, names like 'ultimium' or 'extremium' were considered for Pu because of the erroneous belief that this element might be the heaviest possible in the PTE"


 * "We can expect new elements, perhaps up to nuclear charge 126, in the next decade or so."


 * "Fuzzy concepts like chemical similarity often lead to unnecessary disputes concerning the PTE."

There is a reference here to an interesting article by Restrepo on "Challenges for the periodic systems of elements: Chemical, historical and mathematical perspectives". Sandbh (talk) 01:31, 7 July 2020 (UTC)

Challenges for the periodic systems of elements
Here are some passage from Restrepo’s article:


 * "So, what are the periodic systems of chemical elements? They are neither a classification, nor an ordering of elements, they are both! They are the interweaving of order and similarity relationships of the chemical elements…"


 * "A periodic system of chemical elements results from ordering and classifying chemical elements by some of their properties." [italics added]


 * "Changing similarity criteria brought up another misinterpretation, which is now part of the chemistry folklore: vertical similarities. The fact is that there is no one-to-one relationship between groups of elements (columns in the conventional periodic table) and families of similar elements, not even at the level of electronic configurations. That is, having a column of the table does not always imply that the elements of the column are similar. Likewise, taking similar elements does not always lead to a column of the table. The heuristic works well at the extremes of the table, that is, for alkali metals, noble gases and halogens. However, it is not generally applicable to the other columns."


 * "Surprisingly, from the very beginning (1869) Mendeleev showed that 'in certain parts of the system the similarity between members of the horizontal rows will have to be considered, but in other parts, the similarity between members of the vertical columns.' Further examples of non vertical similarities are the ferrous metals, the lanthanoids, the resemblances of heavier p-block elements with transition metals, of actinoids with transition metals,[21] not to mention those of super-heavy elements with transition metals, the diagonal relationships, those of hydrogen and halogens in crystal structures and the so-called secondary periodicities."


 * "…at the level of possible structures there are many [periodic systems], depending on the properties used to order and classify the elements. The several possibilities for classifying and ordering bring up different periodic systems and their relationships form a super structure. All possible periodic systems lie in that super structure and their relationships are worth exploring. Now comes the question of the possible periodic tables. For a given structure all possible mappings or projections of the structure turn out to be periodic tables."


 * "So, there is no definitive periodic table, what is definitive is the super structure containing all possible periodic systems. Thus, the claim that there must exist a definitive periodic table is too narrow-minded."


 * "We recently spoke about the periodic system as a sculpture, where each of its shadows is a periodic table. It is difficult to have an idea of the sculpture just with one of its shadows. This is like staring at the wall in Plato’s allegory of the cave. We actually think that chemists, unconsciously, in their daily work, use different periodic systems, tailored to their needs."

Sandbh (talk) 03:58, 7 July 2020 (UTC)


 * "The fact is that there is no one-to-one relationship between groups of elements (columns in the conventional periodic table) and families of similar elements, not even at the level of electronic configurations": ah, but there is. Just stop looking at gas-phase configurations and instead ask "how many valence electrons are there and what kinds of orbitals do they go into". Double sharp (talk) 06:25, 7 July 2020 (UTC)

Two cultures
I've been asked (by Eugen Schwarz) a half-scientific question, as follows:


 * "(How far) are the concepts of "The Two Cultures" (chemist C. P. Snow ) and of "Paradigm Shift" and "Scientific Revolution" (T. Kuhn) known among real and computational chemists?

I've never heard of "The Two Cultures" concept. I've heard of "Paradigm shift" and "Scientific revolution" but that is only from reading what Scerri has said about the development of scientific knowledge per A tale of seven scientists.

If anybody else wants to pitch in, feel free to do so.

Thank you --- Sandbh (talk) 00:10, 16 July 2020 (UTC)

An array of periodic tables
What you get from a PT is what you put into it:
 * The IUPAC table is more of chemistry-focused table.
 * The Lu form is more of an idealised table, most "perfectly" expressed in ADOMAH.
 * The La form is more of a pragmatic "no need to lose sleep" table.
 * Al over Sc is more of a metallurgist’s table.
 * In the Earth Scientist's periodic table, group 14 is composed of carbon, silicon, titanium, zirconium, and hafnium rather than the standard set of carbon, silicon, germanium, tin, and lead.


 * In a solid-state physicist's table, both La and Lu, as 5d metals, would go under Y.
 * In an astronomer's periodic table, H and He would be the only non-metals; all the other elements would be metals.
 * A periodic table with H over B and He over Ne would be a nice designer table.
 * In a Pauling EN table, group 3 is B-Al-Sc-Y-La-Ac.
 * In a superconductivity periodic table, group 2 is split into Ba-Ra and Ca-Sr-Yb, and group 12 = Be-Mg-Zn-Cd-Hg.

No doubt it should be possible to construct a periodic table of periodic tables, based on Scerri's notion of a quasi-continuum of periodic tables.

There is the analogy between metals-nonmetals, and philosophy-based v chemistry-based tables.

Consider how many insights and how much understanding could be gained from these stepping stones including, but not limited to the fundamental and important nature of inanimate matter. --- Sandbh (talk) 08:20, 17 July 2020 (UTC)

Plan S update
Plan S is an initiative for open-access science publishing launched in 2018 by a consortium of national research agencies and funders from twelve European countries. It will start in 2021.

Agencies behind the initiative have announced a policy that could make it possible for researchers to publish in any journal they want — even in subscription titles that haven't yet agreed to comply with the scheme.

There was a recent article in the Guardian headlined, "Scientific publishing is a rip-off. We fund the research – it should be free". That article notes that, "half the world’s research is published by five paywall companies: Reed Elsevier, Springer, Taylor & Francis, Wiley-Blackwell and the American Chemical Society."

The update is here. --- Sandbh (talk) 23:39, 17 July 2020 (UTC)

Good news about Meitner, Hahn, and fission
FYI produced great GA-worthy articles about Meitner, Hahn, and Discovery of nuclear fission. All three deserve a GA-status, imo.

Also, reading those aricles was a true pleasure. -DePiep (talk) 21:21, 18 July 2020 (UTC)

Recent attempts to change the periodic table (Scerri 2020)
Here. Sandbh (talk) 23:42, 17 July 2020 (UTC)
 * I claim authority on the Periodic Table number of columns topic. -DePiep (talk) 20:51, 18 July 2020 (UTC)

Here are some extracts from, and commentary on, this interesting article:

Philosophy v pragmatism? The focus of the paper is philosophy rather than pragmatism. (p.2)

I suggest a need to focus on philosophy and pragmatism.

Focusing on just one results in needless arguments, including of the kind I used to make.

Insisting on one PT Scerri writes:


 * "There is no need to insist on the periodic table having a format that is suited mainly for the purposes of the chemical community and for chemical educators." (p. 6)

As far as I know, no one has made such an insistence. It is rather a case of people insisting on such a table within a particular sub-context or interest dependence, and usually not making this clear enough.

Who owns the PT? Scerri writes:


 * "The periodic table has now become as much the property of physicists, geologists, astronomers and others as it is of its chemical originators." (p. 7)

This is a contentious generalisation.

I suggest the periodic table, in the first instance, remains the organising icon of chemistry. Thus, here is what Scerri said in the 2nd (2020) edition of his Red Book:


 * "…it helps to remember that, when all is said and done, the periodic table remains primarily in the domain of chemistry, although the relationship between chemistry and the underlying explanation from physics remains as the underlying theme… (p. ix)"

Rather than becoming a shared commodity, the periodic table concept has been borrowed, adapted, tailored and presented in various different guises—including the 15-element wide f-block version—by the physicists, geologists, astronomers and others.

As Scerri rightly says:


 * "It becomes increasingly clear that there may not be any such thing as one optimal table in a purely objective sense. The question seems to depend on what criteria are considered and, most importantly perhaps, on whether one favours chemical or physical criteria or general didactic considerations." (p. 12)

To this commendable end, he goes on:


 * "We should accept that a degree of convention must be used in selecting a periodic table that can be presented as perhaps the best possible table that combines objective factors as well as interest dependence." (p. 14)

Quite so, having regard to the priorities of each interest group.

The Madelung Rule


 * "In any case, it is interesting to see that Pyykkö admits that it is surprising, in view of the relativistic effects, that the Madelung rule survives so well all the way up to atomic number 172." [!] (p. 8)

As far as the MR anomalies/symmetry breaking we observe in real life are concerned, the analogy is to an aeroplane experiencing turbulence. The flight path always returns to normal, after each turbulence episode.

The MR can also be regarded as the "spine" underlying the pattern of free atom electron configurations. The spine has bumps, dips, and knobbly bits on it, but still runs "true", so to speak.

Group 3


 * "While the majority of textbook and other periodic tables in the 18-column format show the elements of this group as scandium, yttrium, lanthanum and actinium, a significant number of more recent tables feature the last two elements as lutetium and lawrencium instead." (p. 10)

Serving the largest audience Scerri seems to go off-message in his conclusion, with references to:


 * "…the format of the periodic table that serves the greatest number of periodic table users including students, instructors and practising chemists alike"; and


 * "…how the periodic table is presented to the widest possible audience of users." (p. 15)

Surely the result of these notions will be a periodic table that attempts to cater to everyone but pleases no one?

Going off-message at this point is peculiar, since he earlier wrote:


 * "It becomes increasingly clear that there may not be any such thing as one optimal table in a purely objective sense. The question seems to depend on what criteria are considered and, most importantly perhaps, on whether one favours chemical or physical criteria or general didactic considerations." (p. 12)

Accordingly, give me a tailor-made PT anytime, whether that is 14CeTh, 15LaAc, or 14LaAc, Adomah, AAE, Janet or some other variation, as long as the applicable context is set out.

The bugaboo of the split s-block Scerri notes the periodic table is generally depicted with helium in group 18, and this splits the s-block (p. 11).

This is one of those things—the split s-block—that effectively all chemists (to a first approximation) do not lose any sleep over.

Same goes for the split d-block, which is less visible.

That said, better chemists keep both of these interesting aspects of the PT in mind.

It is like what Jones says:


 * "Scientists should not lose sleep over the hard cases. As long as a classification system is beneficial to economy of description, to structuring knowledge and to our understanding, and hard cases constitute a small minority, then keep it. If the system becomes less than useful, then scrap it and replace it with a system based on different shared characteristics." Jones 2010, Pluto: Sentinel of the outer solar system, Oxford University Press, p. 171).

The anomalous first period
 * "Another attractive feature of the left-step table is that it restores regularity and perhaps even balance to the otherwise awkwardly shaped traditional periodic table representation. More significantly than such aesthetic considerations, this table provides greater regularity in depicting every single-period length as repeating once as, 2,2,8,8,18,18,32,32. Meanwhile, the traditional table features an anomalous first period that, unlike all subsequent ones, does not repeat in length to give a sequence of 2,8,8,18,18,32,32. (p. 13)

I don't understand why the lack of repetition of the length of the first period is regarded as anomalous. There is no first principles derivation being breached here, as far as I know. It only means that, from a chemistry perspective, it is more meaningful to break the periods after the end of the noble gases. At the same time, the left step table is still good for its particular uses.

Thorium
 * "Needless to say, the characterization of these blocks of the periodic table is only approximate, just as the assignment of electronic configurations to atoms represents an approximation. Moreover, one may readily concede that an element such as thorium does not actually possess any f-orbital electrons and yet it is classified as being among the f-block elements even in all four of the periodic table representations shown in figures 10 to 13.

--- Sandbh (talk) 00:39, 19 July 2020 (UTC)

Archive 48
I've created this and will progressively move group 3 content from this page into it.

The mega-thread will then occupy archives 42-44-46-48. Sandbh (talk) 23:56, 21 July 2020 (UTC)


 * Archiving complete. Sandbh (talk) 00:19, 22 July 2020 (UTC)

Forthcoming special issue on the periodic table
Philosophical Transactions of the Royal Society A

Mendeleev and the periodic table

Editors: Peter Edwards and Russell Egdell and Dieter Fenske

Online 17 August 2020 —- Sandbh (talk) 10:07, 24 July 2020 (UTC)