Talk:Periodic table/Archive 17

Plenty of Space in Row 1
Tranquillityite, Armalcolite and Pyroxferroite while not presently considered "elements", with proper attribution as lunar elements and verified magnetic system properties, fit nicely on Row 1 of the Table of Elements. Tranquillityite would sit (no headaches, please!) to the Left of Element 1 in a "new" 0 Column, and Armalcolite and Pyroxferroite would reside between Hydrogen and Helium in columns 13 and 17.

How do we make this discussable? Wikimagcarta (talk) 15:17, 22 March 2023 (UTC)
 * You make this discussable by proposing a specific change cited to reliable sources. Tranquillityite, armalcolite, and pyroxferroite are mineral compounds made from elements; they are not elements themselves, so they have no place in a periodic table of elements. ~Anachronist (talk) 15:21, 22 March 2023 (UTC)
 * They have no place in a periodic table of elements if magnetism has no attributable rigor in a periodic table of elements.
 * Out of curiosity, and in a world of 8 billion people, may I ask what it is you get paid for employment for a living? Wikimagcarta (talk) 15:24, 22 March 2023 (UTC)
 * It sounds like you're proposing original research to be included in the article. That is not permitted; see No original research. As for me, my life outside of Wikipedia isn't relevant here; you can always look at my user page for more information about that. ~Anachronist (talk) 15:35, 22 March 2023 (UTC)
 * These are minerals rather than elements, so their inclusion in a periodic table of elements is inappropriate. And if there are no reliable sources describing these claims, there's nothing to discuss, as they would constitute original research. Complex / Rational  16:00, 22 March 2023 (UTC)
 * General Idea Consensus may and do consider them "minerals", but they are not elements of this Earth. They are of a body and environment more radioactive in time and space than any element can and has been organized here by scientists and mathematicians under the auspices of our elementary atmosphere and biosphere.   In my opinion, and proof, they are elements, and they do compliment our present organization on the table, but I cannot print my own work here, so we are left to the will of our publishers at large whom I have already submitted to enough without equality nor equity. Wikimagcarta (talk) 19:23, 22 March 2023 (UTC)
 * Then it is also beyond the bounds of anything to be included on our articles or even discussed further on their talkpages. Best of luck in your future research. DMacks (talk) 20:45, 22 March 2023 (UTC)
 * You know, DMacks, I am offended having been a user of Wikipedia for years now, by your smug comment.
 * Do you know when any first responders who are also contributors to the Tides, Periodic Table, and Magnetism academia here will arrive to this conversation? 209.222.202.31 (talk) 14:36, 23 March 2023 (UTC)
 * You've been answered by three editors, and seriously at that. You are invited to digest the contents. I'd say there is enough in there to call a Finito. Also, already twice you've gone off-topic & into personal, so there's a limit too. HTH DePiep (talk) 14:46, 23 March 2023 (UTC)
 * I have worked with Quickbooks, pencil and paper general ledgers, accounting for every expenditure and receivable for legitimate business here on planet Earth. Your definition of "editor" may be different than mine, NAICS, and SIC code ordinance.
 * Perhaps you can show me the way to Wikipedia's conference tables and real estate office space because there are many people in need regardless of the rhetoric industry. 209.222.202.31 (talk) 15:26, 23 March 2023 (UTC)

Elephant shaped periodic table?
In the alternative periodic table section, it says: "circles, triangles, and even elephants", it sounded strange and I wondered if it was some trolling or vandalism, so I went to check it up, and it points to a Nature article. that does contain "The periodic table has been mapped onto spirals, circles, triangles and even elephants", and that uses the book "The Periodic Table: Its Story and Its Significance" by Eric Scerri as a source.

So I downloaded the book, but I could not find the word "Elephant" in that book, and nor does it contains any periodic table shaped like an elephant. My suggestion would be to remove that Elephant statement or if someone back it up by other source. -- Arthurfragoso (talk) 14:52, 19 March 2023 (UTC)


 * Not in my hardcopy either. So pls remove indeed. -DePiep (talk) 15:18, 19 March 2023 (UTC)
 * 10.1021/ed086p1149. But I'm not sure this idea of incorporating the periodic table into an artistic mapping is comparable to the actual periodicity concept. DMacks (talk) 18:08, 19 March 2023 (UTC)
 * This. Though structural variants have a place. In general, elephants should not be kept behind a paywall. DePiep (talk) 19:45, 19 March 2023 (UTC)
 * True… 122.171.21.0 (talk) 09:53, 31 March 2023 (UTC)

RfC: 4-color PT or 1-color PT
Interested editors are invited to participate in a discussion affecting this page at. YBG (talk) 03:13, 24 May 2023 (UTC)

Improving the flow of the structure of the article
To improve the flow and balance of the first two sections I've rearranged things as follows:

Before, I felt there was too much technical content in the first section—which is supposed to be an overview—dealing with atomic structure and electron configurations. As well, atomic structure is important enough to merit its own section.

After, the "Overview and variations" section now has more of an holistic flavour, before moving on to look under the hood in the next section, "Atomic structures of the elements."

In the process I trimmed some duplicated content at the head of the original "Overview" section. --- Sandbh (talk) 06:38, 4 June 2023 (UTC)

Typo
The article includes an obvious typo, but I’m not sure how to correct it. could you or someone else please fix this? YBG (talk) 22:49, 4 June 2023 (UTC)
 * it now says “The realisation that lanthanum is not an d-metal …”
 * should it say “The realisation that lanthanum is not d-metal …”??
 * or should it be: “The realisation that lanthanum is not an -metal …”??
 * The first. Done. Double sharp (talk) 09:37, 5 June 2023 (UTC)

Missing element, literally
In the section called "the order of subshell filling" there are a few tables, but the last table is missing Helium. It's immediately above the section called "electron configuration table." Please fix this oversight. RowanDreamer (talk) 04:11, 4 October 2023 (UTC)


 * It is right there, in the 32nd column, right above neon. YBG (talk) 04:18, 4 October 2023 (UTC)

Semi-protected edit request on 9 October 2023
This line is wrong. "In nature, only elements up to atomic number 94 exist." It should be "In nature, only elements up to atomic number 92 exist." Neptunium and Plutonium are man-made. 50.230.58.50 (talk) 15:54, 9 October 2023 (UTC)
 * Red information icon with gradient background.svg Not done: Neptunium and plutonium are found in trace amounts in nature, being radioactive-decay products of uranium. DMacks (talk) 16:01, 9 October 2023 (UTC)

History
It should start even earlier in 1789 with Antoine Lavoisier’s "Traité élémentaire de chimie, présenté dans un ordre nouveau et d'après les découvertes modernes." Esteban Outeiral Dias (talk) 16:10, 15 August 2023 (UTC)
 * That would belong rather in the history of the concept "chemical element", no? Double sharp (talk) 06:48, 23 October 2023 (UTC)

Image Used for Periodic Table
I think that the image of the periodic table currently used on this page really isn’t good. No lines separating the elements, just four blocks of color.

The image used previously was much better. Really any normal periodic table image would be much better.

The image of the periodic table on the “Chemical Symbol” page is a good example of that. 2600:1700:1EF0:9E30:8056:4084:7DF8:2964 (talk) 14:04, 7 November 2023 (UTC)


 * IP editor. This is a featured article and as such there has been extensive discussion before that choice was made. See for example Talk:Periodic_table/Archive_14. Reaching a new WP:CONSENSUS is possible but I advise against trying! Mike Turnbull (talk) 16:10, 7 November 2023 (UTC)

article title
The title of the article needs to be changed: Table of D.I. Mendeleev. Analogy - any other names of physical phenomena and laws: Ohm's Law, Newton's Law, etc. 46.138.85.90 (talk) 16:01, 17 December 2023 (UTC)
 * See WP:COMMONNAME. NadVolum (talk) 16:11, 17 December 2023 (UTC)


 * This is not a good idea. The common name of the periodic table of the elements is "the periodic table." It is not "Table of D.I. Mendeleev". This same question has been discussed and resolved in previous talk pages for this article. One problem with naming Mendeleev in the title is that over the years after 1869 he proposed many different periodic tables, for he kept improving his first one of 1869 (which was complete for its time but badly flawed from a modern perspective). Another problem is that the history of the periodic system is very complex; over the last 150 years there have been dozens of periodic tables proposed. There were also many rivals of Mendeleev in his own day, and it would be a mistake to reduce that historical complexity to such a simple perspective.Ajrocke (talk) 18:14, 17 December 2023 (UTC)
 * There's a discussion going on at ru.wp to rename their article to acknowledge Mendeleev, but it makes more sense for them than for us. "Mendeleev table" is common in Russian, but not in English. Double sharp (talk) 16:29, 19 December 2023 (UTC)

Is there an element 119 on the periodic table?
Ununennium - Wikipedia Ununennium, also known as eka-francium or element 119, is a hypothetical chemical element; it has symbol Uue and atomic number 119. 70.116.129.172 (talk) 19:55, 19 December 2023 (UTC)


 * Ununennium is a hypothetical chemical element ... that has not yet been synthesized. I think it unwise to include a hypothetical element before it has been discovered or synthesized. Peaceray (talk) 20:05, 19 December 2023 (UTC)
 * If memory serves, we did it with 117 before it was synthesised. But at that point it was the only gap (1–116 and 118 were known), so it made some sense. Including 119 alone doesn't make much sense at present. Double sharp (talk) 05:27, 20 December 2023 (UTC)
 * There is not yet an element 119, but hopefully there will be one soon. :) Double sharp (talk) 02:56, 20 December 2023 (UTC)

Unreliable sources
hey, ! I looked into two sources used here, and I think that both are not reliable. Both are pieces by Andrey Kulsha, and though he is a chemist, he's not really wel-known. scholar has only 4 articles by him and 9 citations.


 * - that's a student's essay, not even a graduate thesis. it's not peer-reviewed.
 * - that's either a draft or preprint, not a peer-reviewed article

I think that both sources need to be removed from an FA on chemistry, but as I'm not a chemist I'll just leave it up to you. Artem.G (talk) 19:09, 5 January 2024 (UTC)
 * And the same sources are used here Extended_periodic_table. If this theory (or proposal) is notable, then it should be mentioned in better sources. Artem.G (talk) 19:30, 5 January 2024 (UTC)
 * Another problematic source is number 20 there - "Есть ли граница у таблицы Менделеева? – Форум химиков". The link is dead, but it's a forum, and this is not a reliable source for any article, especially for a chemistry one. Artem.G (talk) 19:34, 5 January 2024 (UTC)
 * also pinging . Artem.G (talk) 19:38, 5 January 2024 (UTC)
 * The 2011 article is indeed a preprint. I've replaced it with the place it was actually published: But I kept the link to the online preprint on the author's website, since the actual article doesn't seem to be online.
 * And since this establishes the 2011 date, the forum source (which was only being used to establish that anyway) has also been removed. :)
 * As for the 2004 article, it seems to be only used once to explain secondary periodicity. I've replaced it with another source explaining the same thing. Double sharp (talk) 04:13, 6 January 2024 (UTC)
 * hey, thanks for updates! But what make you think that an article that nobody ever cites is worth to include here? Kulsha is a chemist, but from what I just googled he is not an expert on the periodic table, but a lecturer at a lyceum. Why should his proposal even be here? If it was published in 2011 and has just one mention in other publications, then probably it's just not really important. Artem.G (talk) 09:27, 6 January 2024 (UTC)
 * And The wonderful world of substances and their transformations looks like a pop-science book for schoolchildren. I can't find any citation of that book, no review in Russian, and even no ISBN. Artem.G (talk) 09:30, 6 January 2024 (UTC)
 * There's a lot of extended periodic table formats in the literature and all the detailed articles I could find on them are people explaining their own. :D In a way they are all speculative extrapolations, especially past 120. They mostly agree about the chemistry, just not how to show it.
 * I've removed the Kulsha sources from this article. I should note, though, that this was possible precisely because almost everything in them is already found somewhere else. Actually the only thing in Kulsha's article and form missing from some RS is the extension to 172 rather than 164. :) Up to 164 it is exactly Nefedov et al.'s, and Nefedov has an article on ru.wp, and Nefedov et al.'s PT article has 40 citations since 2006. So, it is not a completely different form from everyone else's, but is essentially a slight update to Nefedov with reference to Pyykkö.
 * Since the speculative extrapolation is not really the point of this article, I've simply removed all exemplars and just used the energy levels as an illustration. I do think, however, that this makes the form appropriate for a mention in Extended periodic table – the article specifically about the speculative extrapolations, where all sources I could find are given an illustration. :)
 * P.S. I found the ISBN (click on no. 597 in this list). But yes, it is a pop-science book for schoolchildren. Double sharp (talk) 09:55, 6 January 2024 (UTC)
 * thanks a lot for the investigation and the edits! I understand that the extension is hypothetical, and I agree that it makes sense to mention it in the Extended periodic table article, but I was just really surpised to see a student's essay used in an important chemistry article. And I have nothing against Kulsha, even more - I would be happy to see his articles used as sources because he is from my alma mater :) Artem.G (talk) 16:40, 6 January 2024 (UTC)

Semi-protected edit request on 9 January 2024
The picture is wrong. Lanthanum(57) is not in the Lanthanide series, it's just before it, while Lutetium(70) is. Same can be said for Actinium(89) which is in the Actinide series (it should be just before it), while Lawrencium(103) is just after it (it should be in it). Kindly replace the picture with the correct one. 103.140.26.60 (talk) 11:19, 9 January 2024 (UTC)


 * Red question icon with gradient background.svg Not done: it's not clear what changes you want to be made. Please mention the specific changes in a "change X to Y" format and provide a reliable source if appropriate. Rehsarb (talk) 12:43, 9 January 2024 (UTC)
 * This is discussed in Periodic table. The version of the periodic table you are asking for, with one d-electron filling before the f-block, is based on early, wrong measurements of electron configurations. The vast majority of chemists who have studied the issue seriously agree that the f-series should be La–Yb and Ac–No, and that Lu and Lr are d-elements (see User:Double sharp/Group 3 sources for a compilation of RS), although not all textbooks have been updated to reflect this (just like how many will still say SF6 and other hypervalent molecules involve d-orbitals, which they don't). Double sharp (talk) 03:24, 18 January 2024 (UTC)
 * Bear in mind the periodic table is a classification rather than a theory. So the position of H and He, B and Al, and the composition of group 3 will depend on the perspective of interest at the time.
 * A good example is the table appearing on the IUPAC web site, which shows a 15-wide f-block. From the point of view of modern electron theory, a 15-wide f-block is nonsense. However, in the case of the IUPAC table, the perspective of interest is the chemistry-based similarities among the 15 lanthanides. So their table makes sense, including to many chemists.
 * Now, La was discovered in 1839. Mendeleev published his first periodic table in 1869. La subsequently came to be associated with Group 3, along with Sc and Y.
 * Lu wasn’t discovered until 1907.
 * The initial electron configuration error didn’t change anything with regard to the chemistry involved. Given the physicists were content to leave the periodic table to the chemists, La kept its position under Y, and Lu stayed at the end of the f-block.
 * Since that time, arguments pro and con La in Group 3 have been advanced and will likely continue to be advanced. Whether anything comes of these arguments will only be able to judged over the fullness of time.
 * A similar situation occurred in the 1930s. Before then, B-Al were routinely shown over Sc. And, indeed, the smoothness of physicochemical trendlines going down B-Al-Sc-Y-La is smoother than is the case for B-Al-Ga-In-Tl. Even so, modern electron theory was emerging and B-Al, as p-block elements came to be moved over Ga, never mind the chemistry! This change took until the 1960s to become widely adopted.
 * It does seem bizarre that the IUPAC table emphasizes a 15-wide f-block on chemistry-based grounds while upholding B-Al in Group 13 on electronic grounds and never mind the chemistry.
 * However, as a classification, there is no one true periodic table since its arrangement is subject to the prevailing mores of the time, in terms what perspective, or which perspectives, are considered to be more relevant. — Sandbh (talk) 10:32, 20 January 2024 (UTC)
 * In fact, there was not a "group 3" in the modern sense until the physics was understood. Neither was there an "f-block", noting that Th and U were thought by Mendeleev (and nearly everyone else really) to be in groups IV and VI. For Mendeleev, there was simply a "group III" that split into A and B branches, and he was happy to accommodate both La and Yb into it before he died. (If anything, he thought of cerium rather as the prototype rare earth. Makes sense: it is the most common, and was the second to be discovered.) His discipline Brauner went further (and did not stubbornly cling to the idea that the elements past cerium would continue increasing in valence) and was happy to include almost all the lanthanoids as eka-zirconiums in group IV. Other chemists were happy to put all of them in one group indeed, but disagreed about which one: maybe group IV (thus creating Ti-Zr-(Ce++) in essence), III (creating Sc-Y-*), maybe across both III and IV, and maybe across II to IV. (Noting the existence of Ce4+, a group III placement is a little odd – I suppose Cu, Ag, and Au were a bit of a precedent, but Mendeleev himself was uncomfortable about that). The first time the idea that there's only one element under yttrium really started to gain traction again was with the advent of electronic-based tables, which is when La really got stuck in this position due to mistakes like the one Hund made. Chemically speaking, the lanthanoids are similar enough that Brauner's idea seemed good enough, although the details could be argued with. When chemists did make a choice to put only one rare-earth under yttrium, they chose Lu even when it still hadn't been discovered (Bassett and Werner). This is chemically sensible: due to atomic radii, it is the late lanthanoids that act more like Sc and Y, not the early ones. In old-school rare-earth chemistry, La–Eu are "cerium group", whereas Sc, Y, and Gd–Lu are "yttrium group". (In modern physical terms we can speak of internal periodicity splitting the first seven 4f elements from the last seven.)
 * As can be seen from that, there really isn't any good physical or chemical case for La under Y and no other lanthanoid there. It started as an error from physics, and no chemist had ever considered it before the physics became known (unsurprising because Lu is more like Sc and Y than La is). Once correct electronic configurations were known, the arguments to put Lu there soon started (Landau went halfway, Hamilton went all the way). Unsurprisingly, therefore, the vast majority of authors writing on the issue since then have supported Sc-Y-Lu, since Lu was clearly a better chemical fit than La as a transition metal in group 3, and the one powerful argument against it (electron configurations) turned out to be based on an error.
 * The Sc-Y-* format used by IUPAC was intended as a compromise according to the 1988 report in which it was described; that report admitted that Sc-Y-Lu is supported by not only electron configurations, but also physical and chemical properties. Even if some intention to match the chemistry of the lanthanoids was intended, it falls flat on its face considering the actinoids. After all, below * comes **, and the idea that the actinoids are chemically similar to each other is laughable (which is why the actinoid concept was so hard to accept at first). It was OK for early chemists to have 15 elements below yttrium before transuraniums were discovered, because they thought that Th, Pa, and U were in groups IV, V, and VI respectively: but once the later actinoids were discovered (by 1988 we'd already reached well into the 6d row), that became chemically untenable (it was of course already physically untenable). (The presence of +4 oxidation states in some lanthanoids of course continues to be an irritant if you want to place them in group 3.) On balance, therefore, it seems more likely that the idea behind it was to compromise rather than to actually fit chemistry.
 * So, the situation for group 3 is somewhat different from the situation with hydrogen and helium. With helium in group 2, you have the situation in which physicists focused on the theoretical basis of periodicity and the Madelung rule tend to favour He-Be, but almost all chemists would rather have He-Ne for the obvious reasons. So that situation does indeed depend on what perspective you consider relevant. On the other hand, arguments in favour of Sc-Y-Lu over Sc-Y-La come from both physicists and chemists.
 * (For the source for my historical assertions, see .) Double sharp (talk) 11:17, 20 January 2024 (UTC)
 * Thank you Double sharp. That was a good read.
 * 1. Regarding, "In old-school rare-earth chemistry, La–Eu are 'cerium group', whereas Sc, Y, and Gd–Lu are 'yttrium group'." According to Trifonov (1963, pp. 37–38), the long-established division of the "rare earths" into the cerium and yttrium groups was for Ce-Gd and Tb-Lu. Trifonov RN 1965, The Rare-Earth Elements, The MacMillan Company, New York. The division was established by Wilhelm Klemm and "has now been quite generally adopted": Oesper RE 1952, Wilhelm Klemm, Journal of Chemical Education, 29(7), 336.
 * 2. Re, "there really isn't any good physical or chemical case for La under Y", multiple good physical and chemical arguments in support of La in group 3 are set out in (19 citations), and in Vernon R 2023, The location and composition of Group 3: A follow-on examination, ChemRxiv (235 views, 249 downloads).
 * 3. The compromise mentioned in the 1988 IUPAC report was between Lu in Group 3, and the observation that, "Most periodic tables in textbooks and classrooms, however, list Sc, Y, La, and Ac as elements of the scandium group and designate the elements Ce to Lu and Th to Lr as lanthanides and actinides". It works in the sense of maintaining continuity across the lanthanide series (orginally La to Lu). The IUPAC report further relied on papers by Christyakow, Fluck (who refers to Landau, and Seel), Jensen (who refers to Christyakow), Landau & Lifshitz, Luder (relying on electron configuration regularity), and Seel (who eventually relies on Jensen). I addressed Landau & Lifshitz's puzzling article in the appendix to my 2020 article on the location and composition of Group 3. A more plausible interpretation is that they supported lanthanum and lutetium in group 3. Jensen's article was criticised by Scerri for being too selective in its arguments. Original arguments in the literature in favour of Lu and group 3 are quite limited and the successive articles that have addressed this question very largely recycle the same few arguments.
 * 4. Regarding the actinides, and any possible intention of matching the chemistry of the lanthanides, Scerri (2021, p. 132) noted that the level at which a science operates is a question for its practitioners and the deepest most fundamental bases are not necessarily the best for all purposes. That is to say, it does not matter that the actinides have a more complex chemstry than the lanthanides. In any event, the An (and Ln) are united by all of them being known in the +3 oxidation state. Scerri E 2021, The Periodic Table: its Story and its Significance, 2nd ed., Oxford University Press, London.
 * 5. No, the situation for group 3 is not different from the situation with H and He. It all comes down to the perspective of interest. Effectively no one cared about the mistake in electron configurations since nothing changed about the chemistry of La and Lu. Sandbh (talk) 06:06, 21 January 2024 (UTC)
 * The point is that lanthanum was always historically part of the cerium group, whereas Sc, Y, and Lu were part of the yttrium group. In other words, even if we speak in terms of chemical similarity, there is no case for La below Y. Jensen makes this point very clear. As for the placement of Gd, at least from what I read it was the first yttrium group element, and that is confirmed by Ullmann . It is possible that, being a borderline case near the middle, different authors historically had different opinions, but at least at present the situation is as I wrote: the cerium group elements are La through Eu.
 * The linked papers supporting Sc-Y-La are mostly repeating the old irrelevancy about the lanthanum atom not having a 4f electron, or more generally the same old irrelevancies about gas-phase electron configurations. Thorium is a sufficient riposte to it: what matters is not the bare atom, but the chemical environment. Either that, or they talk about things that are irrelevant to periodicity. For example, clearly covalent vs ionic character has never had anything to do with where you put elements in the periodic table, or else nearly all the p-block groups would have to be torn asunder. The simple fact of the matter is that in physicochemical properties, Lu is much closer to Y than La is, and in electronic/spectroscopic properties, Lu cannot use f-orbitals whereas La can, making Lu obviously more like a transition metal. Those are the clearly relevant facts of the matter and have been looked at from many angles in RS. Effectively, everybody for whom the matter was relevant cared, looking at figures like Gschneidner, Hamilton, Wittig, etc. who realised that the 4f character of La was relevant to their work. And almost all who decided to take a stand on the topic decided that Lu was the correct third member of group 3. Textbooks obviously did not really see the need to care, as they generally leave f-elements and heavy transition metals in general as a specialist graduate topic, but again: supposed octet expansion in SF6 comes to mind. I have no doubt that people will keep teaching it for a while longer, even though it is completely wrong. That does not mean that the idea of sulfur 3d usage should be taken seriously. The idea that lutetium is an f-element will probably take equally long to disappear, but since Landau and Lifshitz, it has been clear to almost all specialists that it doesn't make sense from any angle you look at. Already in 1965 Hamilton could argue not only based on superconductivity and non-hydrogenic 4f orbitals, but simply on the basis of melting points and crystal structures. Double sharp (talk) 11:59, 21 January 2024 (UTC)


 * Re: No. As I understand it, Sc was not traditionally part of either of these groups. In fact the subdivision based on ion configurations...

(La) Ce Pr Nd Pm Sm Eu Gd     f1 f2 f3 f4 f5 f6 f7

(Y) Tb Dy Ho Er Tm Yb Lu      f8 f9 10 11 12 13 14


 * ...is supportive of La under Y, since the f-electron induced Ln contraction starts at Ce and peaks at Lu. After Lu no more f-electrons are being added so the impact of the contraction gradually peters out. Placing Lu under Y splits the f-electron induced Ln contraction into two blocks. It starts in the second element of the f-block at Ce and does not finish until the first element of the d-block at Lu.
 * Re: Not, so, as per Scerri's observation that Jensen was too selective in his choice of arguments.
 * Re: Not so. The first of the linked papers presents ten interlocking arguments (a further half-dozen subsiduary arguments are in the endnotes); the second presents six more arguments in support of La under Y, including on the basis of solid state configurations. Further, gas phase configurations are relevant as they enable the periodic table to be parsed into four major blocks according to the predominant differentiating electron electron in each block, and each block shows distinctive physical and chemical properties.
 * Re: So? That does not mean it cannot be used to inform the question.
 * Re: That Lu may be closer to Y is neither here nor there. What counts is the smoothness of physicochemical trendlines going down the group. Here, La is a better fit than Lu.
 * Re: Not necessarily. That the heavier alkaline earths can use their d-orbitals in chemistry does not make then more like transition metals.
 * Re: Clearly, those are not the relevant facts.
 * Re: Their arguments lacked depth and coverage, and were effectively ignored.
 * Re: No one has ever looked closely at L & L to see what they actually said, rather than focusing on the few words set our in their footnote. I did in the first paper, finding their arguments supported both La and Lu under Y.
 * Re: All of which limited arguments have counter-arguments. --- Sandbh (talk) 02:36, 27 January 2024 (UTC)
 * Firstly, by Lu the 4f electrons are in the core. Yb is the last element where 4f electrons are actually being added, both in the sense of gas-phase configurations (it's already f14s2), and in the sense of chemical activity (it's the last element that can actually use 4f for bonding in compounds like YbO). Consequently, Lu is a member of the 5d series: the relationship between Y ([Kr]4d15s2) and Lu ([Xe]4f145d16s2) is exactly like that between Zr ([Kr]4d25s2) and Hf ([Xe]4f145d26s2), and is exactly analogous to that between Al ([Ne]3s23p1) and Ga ([Ar]3d104s24p1). They all come after a primogenic contraction (4f, 4f, and 3d respectively). This has been known since Chistyakov in 1968. You do not want to look at Sc, all right, it is the smallest of all rare earths and shows some unusual properties because of that. (Though that has nothing to do with group placement; boron is also quite different from its heavier congeners.) But it is still obvious (and was already obvious to classic rare-earth chemists) that Y and Lu are in one bin, and La is in another one. Why, Lu was even found in Y indirectly: Lu was found as an impurity in Yb, which was found as an impurity in Er, which was found in an impurity of Y. La wasn't found that way; it was found as an impurity in Ce instead.
 * There is no relevance of gas-phase configurations, other than as an approximation where one understands not to worry about the little blips at too small a scale for chemistry, as I was doing in the previous paragraph. Which is what Jørgensen already pointed out in 1973 . Everybody knows that, which is why everyone agrees that Th ([Rn]6d27s2) is an f-element, and nobody cares that all three stable elements of the Ni group literally have a different ground state. And the solid-state argument doesn't even support Sc-Y-La because lanthanum metal itself has some 4f contribution, which explains its low melting point. On the other hand, Lu doesn't.
 * There is simply no counterargument to the stark fact that La has chemical activity of f-orbitals and Lu does not, and that such chemical activity exists precisely for 28 elements: La–Yb and Ac–No. That is why Landau and Lifshitz are the first writing on the wall, even if they are at least incomplete: they realised that Lu cannot be an f-element. That already makes the Sc-Y-La form illegitimate, because it puts Lu there. All that is left is either to realise that two elements can't go in the same place without messing up the periodic system, or to realise (as David C. Hamilton did) that La has f-involvement. Again, he realised that in 1965; it's not even news at this point. Talking about covalent vs ionic and all other irrelevancies cannot get around the fact that that is not and has never been what placement in the periodic table is about. First it was about valence (Mendeleev 8-column table), and then it became about electronics (Werner's long-form table), in keeping with two of the three chemical revolutions (we ignore the first one because that had to do with unraveling what an element even is in the first place; before that, no one could even think of drawing a periodic table). That is why H goes over Li, and that is why C can be in the same group as Pb. And it's literally been known since 1915 (Biron's secondary periodicity) that groups usually do not exhibit smooth trends, but display an alternation between even and odd periods. As Chistyakov noted, Sc-Y-Lu fits that, and Sc-Y-La doesn't.
 * P.S. Heavy alkaline earth metals are indeed somewhat like transition metals because they can use the d-orbitals (especially barium is quite adept at it). That is well-known by now. The difference is that they at least manage to use s-orbitals as well. That's not at all the same kind of situation as putting Lu in the f-block when it literally can't use f-orbitals for any chemistry. Double sharp (talk) 16:04, 27 January 2024 (UTC)
 * Interlude: A sequel to Jensen's three revolutions. Grim reading. --- Sandbh (talk) 03:28, 3 February 2024 (UTC)

Re:

From a chemistry perspective, it is the trivalent cations that are important. Here, the configurations are:

f1 f2 f3 f4  f5  f6  f7  Ce Pr Nd  Pm  Sm  Eu  Gd

f8 f9 f10 f11 f12 f13 f14 Tb Dy Ho Er  Tm  Yb  Lu

More specifically, the filling of the 4f sub-orbital is the raison d’etre of the Ln metals (Ce to Lu). While 4f electrons rarely participate in bonding interactions they contribute to the Ln contraction starting in Ce and culminating in Lu, and the uniform and characteristic +3 oxidation state among the metals concerned (Mingos 1998, p. 375; Cotton 2006, p. 12).

Re:

Well, no. In terms of chemical separation behaviour, that Sc, Y and Lu occurred in the so-called "Y" group, and that La occurred in the “Ce” group did not imply anything particularly significant; it is simply a reflection of the increasing basicity of these elements as atomic radius increases. Taking the alkaline earth metals as another example, Mg (less basic) belongs in the “soluble group” and Ca, Sr and Ba (more basic) occur in the “ammonium carbonate group”. Moving Lu under Y because they occur in the same chemical separation group fails to consider separation group patterns elsewhere in the periodic table.

Further, the separation group behaviour of Y can be ambiguous, and Sc, Y, and La appear to show complexation behaviour different to that of Lu. As observed by Vickery (1960, p. 37):


 * "In separating Y from the heavy Ln, advantage is always taken of the phenomenon by which Y sometimes assumes characteristics similar to those of the light Ln, and sometimes follows the heavy Ln in behaviour."

Over a decade later Vickery (1973, p. 344) observed that:


 * "Polymerization of the Y ion has been shown now to account for its apparently nomadic behaviour in earlier classical separation techniques. Evidence is also available for the existence of La hydroxy-polymers in solution. There is, indeed, to be seen an interesting sequence through…Group III in this respect. Hydroxyl bridged polymerization has been shown for Al, Sc, Y, and La ions, but does not appear to exist with the series Ce3+ → Lu3+. On the other hand, Ga, In and Tl do appear to complex in this fashion. On a thermodynamic basis, ionic hydration—or hydroxo complex formation—may depend upon free energy rather than enthalpy and plots of such free energy link the pre-lanthanon triad more closely to Al, on the one hand, and Ge, etc., on the other, than to the Ln group of elements.

The chemists who kept La under Y were on the mark, chemically speaking.

Re:

In fact Y is unique among the rare earth elements in that, depending on the circumstances, it can behave like a light Ln e.g. Pr, Nd, Sm, or a heavy Ln e.g. Dy, Tm, Lu (Marsh 1947, p. 1084; Jowsey et al. 1958, p. 64; Bünzli and McGill 2011, pp. 19, 26; Gupta and Krishnamurthy 2005, p. 165). In terms of the stoichiometry of binary compounds, Y is reported to be more like La than Lu (Restrepo (2018, pp. 94–95). In a similar vein, La has a sufficiently distinct nature compared to the Ce to Lu series (Liu et al. 2019).

Re:

In fact, no less than Scerri argued for the use of gas phase configurations on the basis of the dominant differentiating electron in each periodic table block:


 * “…for the purpose of selecting an optimal periodic table we prefer to consider block membership as a global property in which we focus on the predominant differentiating electron.” (Scerri and Parsons 2018, p. 151).

It is a simple enough exercise to show that with La under Y there are a total of 12 differentiating electron discrepancies whereas with Lu under Y there are 13.

Re:

For Lu, Ratto, Coqblin and d'Agliano (1969, pp. 498, 509) suggested that its lack of superconductivity might be attributable to a small 4f character.

A few other authors referred to some of the properties of Lu being influenced by the presence of its filled 4f shell: Langley 1981; Tibbetts and Harmon 1982; Clavaguéra, Dognon and Pyykkö 2006; Xu et al. 2013; Ji et al. 2015. The most surprising of these is likely to have been Clavaguéra and colleagues, who reported a pronounced 4f hybridisation in LuF3 on the basis of three different relativistic calculations. Their findings were questioned by Roos et al. (2008) and Ramakrishnan, Matveev and Rösch (2009). More recently Ji et al. (2015) found errors in bond lengths and energies if the presence of a full 4f shell was not taken into account.

An analogous situation certainly occurs at the end of the d-block, in group 12. Zinc and cadmium have HCP crystal structures with c/a ratios of 1.856 and 1.886, much higher than the ideal value (of 1.633). These deviations have been attributed to covalent bonding contributions arising from hybridisation of the filled d band with the conduction band (Steurer & Dshemuchadse 2016, p. 207). Condensed mercury has a distorted structure, and mixed metallic-covalent bonding (Steurer & Dshemuchadse 2016, p. 207; Russell & Lee 2005, p. 354).

In terms of condensed phase configurations, La represents the first occurrence of a 5d electron and Lu the thirteenth. There is no prima facie case for skipping La in favour of Lu.

In a lanthanum table, the number of f-electrons, for the elements in their condensed states, is congruent with the place of each f-block element in 12 of 14 cases; in a Lu table the situation is reversed, with congruency seen in only 2 of 14 places.

Another way of putting it, is that in terms of condensed phase configurations, and in an La table, the 4f row starts regularly whereas the 5f row starts with one irregulary. OTOH, in an Lu table the 4f row starts with six irregularities and the 5f row starts with ten irregularities,

Re:

The counterargument is that 4f electrons rarely participate in bonding interactions and that the more important consideration is the 4f-induced Ln contraction starting in Ce3+ and peaking in Lu3+. Further, "...its 4f character, if there is one, is in any case very small (B. Coqblin 1977, The Electronic Structure of Rare-earth Metals and Alloys, Academic Press, p. v).

Re:

In fact, L&L did not put the writing on the wall, given they placed La above Lu. See, specifically, L&L's depiction of the "Platinum group", as they labelled it.

Re:

In fact, it was Scerri who wrote that: "Chemically similar groups should be close together, either as vertical groups or horizontal triads, with links between related elements clearly visible." (Scerri 2004, p. 138) Now, it is well known that group 3 are more like groups 1 and 2 than group 4. It then follows that in the 32-column table, group 3 should be adjacent to group 2 rather than group 4. This can only be achieved with group 3 as Sc-Y-La.

Re:

It was not fundamentally about valence. Instead it was about the periodic law, expressed by Mendeleev as:


 * "The measurable chemical and physical properties of the elements and their compounds are…[an approximate] periodic function of the atomic weight [now Z] of the elements."

Valence was used by Mendeleev as an initial sorting rubric. Werner's long form appeared before the structure of the atom was known, before the importance of atomic number was recognised and before quantum mechanics had been developed.

As far as the periodic law is concerned, the smoothness of physicochemical trendlines going down (B-Al-)Sc-Y-La is better than that going down (B-Al-)Sc-Y-Lu.

Re:

Chistyakov's (1968) article is too short (2 pp.) and too selective to draw any conclusions from. Further, as with Jensen, Chistyakov only looked at one-half of the situation. Both authors failed to mention the fact that the trends going down Sc-Y-La were more like those going down -Ca-Sr-Ba and -K-Rb-Cs.

Re:

Your point was that, "Lu cannot use f-orbitals whereas La can, making Lu obviously more like a transition metal." Here in, the same way that Ba is not more like a transition metal in its chemistry, neither is Lu more like a transition metal. --- Sandbh (talk) 02:11, 3 February 2024 (UTC)


 * Bünzli J & McGill I, Rare-earth elements. In: Elvers, B. (ed.) Ullmann’s Encyclopaedia of Industrial Chemistry, 7th edn, Wiley-VCH, Wiesbaden (2011)
 * Clavaguéra C, Dognon J-P & Pyykkö P, Calculated lanthanide contractions for molecular trihalides and fully hydrated ions: The contributions from relativity and 4f-shell hybridization, Chemical Physics Letters, vol. 429, nos. 1–3, pp. 8–12 (2006)
 * Cotton S, Lanthanide and Actinide Chemistry, Wiley, Chichester (2006)
 * Gupta CK & Krishnamurthy N, Extractive Metallurgy of Rare Earths, CRC Press, Boca Raton (2005)
 * Ji et al. 2015, Ionic bonding of lanthanides, as influenced by d- and f-atomic orbitals, by core-shells and by relativity, Journal of Computational Chemistry, 36(7), 449–458.
 * Jowsey J, Rowland RE & Marshall JH, The comparative deposition of yttrium, cerium, and thallium in bone tissue of dogs. In: Argonne National Laboratory, Radiological Physics Division Semiannual Report, July to December 1957, Illinois, 63–75 (1958)
 * Langley RH, Structure and phase transitions of the lanthanide metals, Journal of Solid State Chemistry, vol. 38, no. 3, pp. 300–306 (1981)
 * Liu R, Mao G & Zhang N, Research of chemical elements and chemical bonds from the view of complex network, Found. Chem., 21, 193–206 (2019)
 * Marsh JK, The relation of yttrium to the lanthanons: A study of molecular volumes. J. Chem. Soc., 1084–1086 (1947)
 * Mingos DMP, Essential Trends in Inorganic Chemistry, Oxford University Press, Oxford (1998)
 * Ramakrishnan R, Matveev AV & Rösch N, The DFT + U method in the linear combination of Gaussian-type orbitals framework: Role of 4f orbitals in the bonding of LuF3, Chemical Physics Letters, vol. 468, nos. 1–3, pp. 158–161 (2009)
 * Ratto CF, Coqblin B & d'Agliano EG 1969, Superconductivity of lanthanum and cerium at high pressures, Advances in Physics, vol. 18, pp. 489–513
 * Restrepo G, The periodic system: A mathematical approach, In: Scerri & Restrepo (2018)
 * Roos et al. New relativistic atomic natural orbital basis sets for lanthanide atoms with applications to the Ce diatom and LuF3, Journal of Physical Chemistry A, vol. 112, no. 45, pp. 11431–11435 (2008)
 * Russell AM & Lee KL, Structure-property relations in nonferrous metals, Wiley-Interscience, New York (2005)
 * Scerri E & Restrepo G (eds.): Mendeleev to Oganesson: A Multidisciplinary Perspective on the Periodic Table, Oxford University Press, New York (2018)
 * Scerri, E.R., Parsons, W.: What elements belong in Group 3 of the periodic table? In: Scerri, E., Restrepo, G. (eds.) Mendeleev to Oganesson: A multidisciplinary perspective on the periodic table, pp. 140–151. Oxford University Press, New York (2018)
 * Steurer W & Dshemuchadse J, Intermetallics: Structures, properties, and statistics, Oxford University Press, Oxford (2016)
 * Tibbetts TA & Harmon BN, "The electronic structure of Lu", Solid State Communications, vol. 44, no. 10, pp. 1409–1412 (1982)
 * Vickery RC, The Chemistry of Yttrium and Scandium, Pergamon Press, New York (1960)
 * Vickery RC, Scandium, yttrium, and lanthanum, In: Bailar Jr et al. (eds.), Comprehensive Inorganic Chemistry, vol. 3, pp. 329–354, Pergamon Press, Oxford (1973)


 * From a chemistry perspective, the valence orbitals are important, not configurations of cations. If we were to stick to cations, we would conclude that both Cs+ and Ba2+ are s0, and thus that neither are s-elements. And likewise, Sc3+ is d0, so it is not a d-element. On the other hand, Ga3+ is d10, so by your logic it is a d-element after all. Obviously, considering cations leads to complete absurdity, which is why it has no bearing on periodic table placement. The relevant fact is valence activity. (Indeed, the comparison of Sc vs Ga strongly suggests an analogy of La vs Lu.) By the way, in fact La has the biggest 4f valence activity in the entire 4f row, simply because it is so early in the series that the 4f shell is not feeling as much effective nuclear charge. Just look at the tables in : only Ce comes anywhere near it. Lu, of course, has none at all. So your counterargument does not work: cutting La out of the 4f row removes the element that does the most to involve the 4f orbitals in bonding, whereas cutting Lu out of the 4f row simply removes an element that had no right to be there at all and puts it with its true companions with the same valence manifold. Ji et al. even note that you get more errors in Lu compounds freezing 5p6 than freezing 4f14, which speaks volumes as to how little the 4f shell is really contributing to Lu. Arguing that Lu 4f is a valence shell is tantamount to arguing that the Lu 5p shell in the xenon core also is, which is chemically preposterous.
 * The idea that La is sufficiently different from the other lanthanoids is also preposterous: why do you think they are called lanthanoids? Not that such similarities ever had anything to do with where you place elements in the PT anyway; uranium is put under neodymium, not the much more similar tungsten, and Mendeleev was happy to put H over Li. But this once again shows how Sc/Y/La doesn't even have the chemical facts on its side, which is impressive given that the periodic table is now about electronics first (which is why it separates s, p, d, and f blocks instead of mixing them like Mendeleev's 8-column form).
 * We look at patterns in the correct block. In the early d-block, we find a consistent pattern that the 4d and 5d elements are close to each other and difficult to separate, whereas the 3d element is more different. This holds for Sc/Y/Lu just as it holds for Ti/Zr/Hf and V/Nb/Ta, whereas it does not hold for Sc/Y/La. Obviously the 4d and 5d elements are not exactly identical; they are not isotopes, and it is possible to separate them chemically through laborious fractional crystallisation. The point is simply that they are close in radii and behave more similarly to each other than to the 3d element in the same group. The much more different trends down larger main groups like group 2 are irrelevant; we cannot expect a comparison down five elements, with much more scope for differences in radii, to mimic a comparison of just three. The comparison to K/Rb/Cs and Ca/Sr/Ba is equally irrelevant: we are comparing d-elements, not s-elements or p-elements. B/Al/Sc would just as well fit the trends Li/Na/K and Be/Mg/Ca better, but we don't use it for exactly the same reason: wrong block.
 * The idea that hydroxyl-bridge polymerisation does not occur in lanthanoids other than La is preposterous, and I am astonished that Vickery appears to have thought that half a century ago. How else would they hydrolyse and precipitate out in solution as pH rises? agrees with me (and chemical common sense): they all do. Meanwhile, Restrepo's stoichiometry study has nothing to do with where you put elements in the periodic table. If it did, then why are O and S still in the same group? If we were allowed to throw around properties willy-nilly we could "prove" that any two elements were related (or unrelated) to each other. Jensen has already pointed out that this is nonsense: Self-consistent group and period trends are dictated by the periodic law and by the underlying atomic structure of the periodic table itself, whereas the arbitrary pairing of elements from different rows and columns in the hope that a fortuitous cancellation of trends will lead to property matching is not and is an abuse of the periodic law and table, which violates both criteria 2 and 3. Obviously such an arbitrary “hunt and peck” procedure allows one to prove (or disprove in Lavelle’s case) almost anything. Regrettably this misapplication of the periodic law and table is quite common in the chemical education literature, where it has given rise to some highly problematic results (3–5).
 * The 3d and 4d metals, in the condensed phase, are (n−1)dk−1s1 . So by that logic the d-block would have to run Ca–Cu, not Sc–Zn. The fact that it doesn't strongly suggests that you are throwing around yet another property that has nothing to do with periodic table placement. Why exactly would the condensed phase of the metal be privileged over any other compound, anyway? The periodic table classifies abstract elements, not simple substances, as Scerri has noted. And besides, there's a bunch of gases in the PT that don't even form a condensed phase under standard conditions.
 * Exactly where is the concept of the differentiating electron relevant in chemistry anyway? The process which actively transmutes element Z to element Z + 1 is beta-minus decay, involving much higher energies than the chemical scale. And the idea of the differentiating electron in cases like V 3d34s2 vs Cr 3d54s1 is ill-defined. Here it seems that Scerri is running up against the fact of the matter that nobody cares about this, just as nobody cares about the gas-phase configurations (as Thyssen and Binnemans noted). If people really cared about that, they would be tearing blocks apart to deal with every other Madelung anomaly. But nobody can be bothered, even for Th 6d27s2 which is in exactly the same boat as Ac 6d17s2. Very simply, it has no chemical sense, as is clear from the fact that Nb 4d45s1 and Ta 5d36s2 have different configurations even though they were confused by chemists for decades, whereas even prehistorically no one confused Ag 4d105s1 with Au 5d106s1.
 * If it wasn't about valence in Mendeleev's day, then how come his table gives pride of place to hydride and oxide formulae, and names the groups I through VIII?
 * It's well-known that group 12 is a lot more like the p-block post-transition groups than it is like the preceding transition groups. If we followed your logic on group 3, we would need to somehow split group 11 apart from group 12. Except that nobody does it, proving the irrelevancy of your argumentation.
 * Let us return to the precise, relevant, and decisive point: La can use 4f orbitals for chemistry and Lu cannot. As you have mentioned, Clavaguera et al.'s study was refuted. Lu is thus a transition metal (d-block), because it uses d-orbitals but not f-orbitals for its chemistry. La, using f-orbitals for its chemistry, is clearly not like a transition metal, but rather like an f-block inner transition metal: it matches Ce to Yb, and is just like Ac and Th in terms of having a weirdly anomalous gas-phase configuration that corrects itself in a real chemical environment. As was already noted in 1968: if, however, an essential feature of an nth-row transition element is that the (n + 1)f-shell (if there is one) is full throughout its chemistry, then lutetium is really the first member of the third transition series, and lawrencium (if the 5g-shell does not intervene) is the first member of the fourth. All that the 4f shell in Lu does is act as part of the core, just like it does in Hf, in Ta, and in all subsequent elements. That makes Lu like the other 5d metals: they all share the effect of the Ln contraction in that their cores are [Xe]4f14 and not [Xe], just like all 4p elements have an [Ar]3d10 core and not an [Ar] core. In the electronic sense, Lu is not like the elements Cs to Yb, which have a noble-gas [Xe] core.
 * And yes, Ba is more like a transition metal in its chemistry than Cs. Barium has exactly been called an honorary transition metal. But that's not precisely the same sort of situation. Ba uses 6s, 5d, and 6p, so there's nothing wrong with putting it in the 6s block. The problem is that Lu only uses 6s, 5d, and 6p as well, so there is something very wrong with putting it in the 4f block. That is why Landau and Lifshitz are the first writing on the wall: they took the important step to realise that Lu is not an f-element. Once that is realised, the problem with the Sc-Y-La form is already apparent: that it makes that false claim for Lu. The other half of the argument, it is true, came later: but it was the first blow.
 * Smoothness of B-Al-Sc is like Sc-Y-La (both fail to recognise secondary periodicity), whereas the alternating nature of B-Al-Ga is like Sc-Y-Lu (following secondary periodicity, as Chistyakov wrote). So, if you accept B-Al-Ga, like all of modern chemistry does, then only Sc-Y-Lu makes sense.
 * P.S. Langley et al. 1981 and Xu et al. 2013 put Lu down as having the least 4f usage of any lanthanoid, Tibbetts et al. 1982 note that local density approximation places the Lu 4f levels too high compared to the real situation, and (as I noted above) Ji et al. 2015 notes that Lu 4f is less important than Lu 5p within the xenon core. They are not exactly supporting your point. On the contrary, they are admirably proving that Lu has a [Xe]4f14 core and thus comes after the end of the 4f series. Double sharp (talk) 10:50, 3 February 2024 (UTC)

Janet's left-step table: Irregularity
And any other interested editor.

The text in the Alternative Periodic Tables section currently reads, in part:


 * Janet's left-step table is being increasingly discussed as a candidate for being the optimal or most fundamental form; Scerri has written in support of it, as it clarifies helium's nature as an s-block element, increases regularity by having all period lengths repeated...

I added a footnote after "repeated" saying:


 * "That said, the left-step table introduces a new irregularity, not present in the traditional form of periodic table, in that the sequence of shell numbers at the start of each period is 1, 2, 2, 3, 3, 4, 4... i.e. the sequence is duplicated in all cases but the first."

You reverted this addition on the grounds of no citation being applied.

Could you clarify your position? The fact that the LSTP has an irregular sequence of shell number starts is evident from a simple counting of the numbers shown in the margin on the left side of the LSTP in the immediately following LSTP in the article. Here it is again:

I had thought that a simple counting of numbers, as 1, 2, 2, 3, 3, 4, 4, 5 etc would not need a supporting citation.

Thank you. Sandbh (talk) 12:03, 7 February 2024 (UTC)
 * The issue at stake, that requires a citation, is whether anyone else considers this an irregularity or even an important desideratum for periodic tables. One could list any number of numerological regularities or irregularities in the standard table as well, such as the fact that Fibonacci-numbered elements always start half-rows of blocks until the pattern breaks down at 144. But even though they are obviously evident from counting, saying it is a regularity or irregularity requires a source. This is pretty much a textbook case of WP:SYNTH: conclusions drawn (i.e. in this case the idea that this is a significant irregularity that counters Scerri's statement) must be in some RS.
 * Also note that it would be mathematically impossible for 1 to occur twice, as there is only one subshell with n = 1: 1s. Therefore, there is even a clear reason to doubt the relevance of the irregularity. Double sharp (talk) 12:12, 7 February 2024 (UTC)
 * The reason that numbers are repeated is that each odd numbered row begins with the same number as the preceding even numbered row. The first odd numbered row (#1) has no preceding even numbered row (#0) to match. Hence, the irregularity being noticed is logically equivalent to saying that the first row is the only row that lacks a predecessor, an anomaly that the traditional PT shares. YBG (talk) 22:34, 7 February 2024 (UTC)
 * More to the point, the Janet table doesn't really care about n. That's not its job. It cares about n + ℓ. outright mentions that it replaces n rows with n + ℓ rows (footnote on p. 83). So it's about like asking why the usual PT has a bunch of columns where the group oxidation state can never be reached: that is no longer the point, so it is not a legitimate reason to criticise it. That would well explain why nobody seems to have made this criticism in the literature. Double sharp (talk) 03:09, 8 February 2024 (UTC)
 * Scerri's dislike of the conventional periodic table (CPT) is well-known, and focuses on its irregular period lengths—2, 8, 8, 18, 18, 32, 32—highlighting the non-repetition of the initial length of 2 as a significant irregularity. In contrast, he advocates for the left-step periodic table (LSPT) due to its uniform period lengths: 2, 2, 8, 8, 18, 18, 32, 32, presenting this regularity as a rectification of the CPT's flaw.
 * However, what Scerri overlooks is a distinct irregularity introduced by the LSPT, absent in the CPT. Specifically, the LSPT's sequence of principal quantum numbers (n) at the start of each period shifts to 1, 2, 2, 3, 3, etc., diverging from the CPT's orderly progression of 1, 2, 3, 4, 5, 6, 7. This modification results in a scenario where the n value of 1 does not recur, contrasting with the consistent sequence observed in the CPT.
 * This particular irregularity is readily observable through simple counting, directly from the table's presentation within the article.
 * Discussing the sequence of n values in periodic tables, such as the CPT and the LSPT, by pointing out the n values through straightforward counting of elements or positions on the table constitutes a factual observation. It does not constitute synthesizing new conclusions from multiple sources or introducing original theories; rather, it is a direct observation and report on the structure as depicted in the table. Thus, it does not fall within WP:SYNTH, since it aligns with WP:CALC.
 * The footnote regarding the LSPT is not a critique based on mathematical impossibilities, nor does it seek to draw parallels with anomalies in the CPT or to question the LSPT's priorities. The aim is to ensure a balanced perspective on the LSPT by noting that, effectively, while it corrects one irregularity of the CPT, it introduces another concerning the sequence of n values.
 * This insight is vital for an understanding of the periodic table's design, underscoring the importance of evaluating both the strengths and limitations of models like the LSPT. By being exposed to these details, readers are better equipped to grasp the complexities involved in accurately and effectively representing elemental properties and behaviors. The intention is not to undermine the LSPT's value but to promote a holistic examination of its contributions and the challenges it presents within the context of periodic table design. --- Sandbh (talk) 12:03, 9 February 2024 (UTC)
 * So, give us a cite saying that that's important. Otherwise, how do we know that it's a relevant critique, especially when we have an RS pointing out that LSPT is not really based on n at all? Double sharp (talk) 12:13, 9 February 2024 (UTC)
 * I don't have a citation about the irregularity of n values at the start of periods in the LSPT. The quite limited literature on the LSPT appears to focus on the regularity of its period lengths, and attempts to jusify He over Be. However, a citation may not be strictly necessary. WP:NOTCITE discusses instances where a source or citation might not be required, offering examples of general common knowledge, such as "The capital of France is Paris" or "Humans normally have two arms and two legs." While WP:NOTCITE is an explanatory essay rather than an official policy or guideline, its substance is instructive.
 * That the LSPT is based on n + l does not mitigate the introduction of a new irregularity namely that the values of n at the start of each row now become irregular, unlike the regular values of n at the start of the CPT. This new irregularity is a direct consenquence of the LSPT's foundational principle based on n + l.
 * This irregularity in the LSPT, while not constituting "common knowledge" in the broadest sense, is a straightforward observation about the table's structure, verifiable by anyone through direct examination.
 * Aligning with the WP commitment to accuracy and comprehensiveness, such factual observations—especially those that can be directly verified without the need for specialized knowledge or interpretation—significantly contribute to our collective understanding. Including this detail offers a more comprehensive, nuanced, and balanced view of the LSPT's design, adhering to the spirit of Wikipedia's standards for verifiability and reliability. Sandbh (talk) 11:30, 10 February 2024 (UTC)
 * So, you don't have a cite, and you admit that most sources discussing LSPT don't focus on this. Therefore, it seems to be in the same situation as the Fibonacci-atomic-number example, and the source-based case for putting it into the article hasn't been made. Double sharp (talk) 11:36, 10 February 2024 (UTC)
 * The Fib example, while interesting, isn't relevant to our discussion on the LSPT's structural irregularity. The focus is on a specific, observable difference in the regulariy of n values between the LSPT and the CPT, not abstract patterns. This irregularity, directly observable and verifiable by examining the image of the LSPT, impacts the understanding of its organizational principles compared to the CPT.
 * I've addressed the lack of a source via WP:NOCITE.
 * WP:PRIMARY allows the use of primary sources for straightforward, descriptive statements that can be directly observed. The argument about the LSPT's n values could be considered a use of the LSPT itself as a primary source for a descriptive observation.
 * WP:FACTS aka WP:BLUESKY is also relevant, as is WP:NOTBLUESKY. Reconciling the two, I suggest, supports the use of editorial discretion in achieving a balance between the rigorous application of the verifiability principle and the practical considerations of contributing to an encyclopedia that is both informative and accessible.
 * WP:COMMONSENSE encourages editors to use common sense and occasional exceptions when interpreting and applying Wikipedia's rules. The inclusion of this observation would significantly contribute to the article's accuracy and completeness without straying into original research (as I've previously explained). --- Sandbh (talk) 06:41, 11 February 2024 (UTC)
 * @Sandbh: Concerning this info about the sequence of n values, we need to consider several aspects:
 * Is it true? (I say Yes, and I believe you agree.)
 * Is it mentioned in RS? (I say No, and I believe you agree.)
 * Are RS required to verify its truth? (I say No, and I believe you agree.)
 * Is it significant? (I say No, but I believe you disagree.)
 * Is its significance mentioned in RS? (I say No, and I believe you agree.)
 * Are RS needed to verify its significance? (I say Yes, but it appears you disagree.)
 * WP:RS says:
 * [W]e publish only the analysis, views, and opinions of reliable authors, and not those of Wikipedians who have read and interpreted primary source material for themselves.
 * And:
 * Wikipedia articles should be based on reliable, published sources, making sure that that have appeared in those sources are covered.
 * This irregularity seems to have been noticed in exactly zero RS, so it falls short of being a significant minority view in terms of significance (though not of truth).
 * In this post, I have not sought to convince you that this irregularity is insignificant, merely that its significance is insufficiently attested for inclusion in WP. Nevertheless, if you show from RS that a significant minority think this irregularity is significant, I will support its inclusion, even if I remain unconvinced of its significance.
 * ——— YBG (talk) 20:30, 10 February 2024 (UTC)
 * Thanks. I believe these matters have been addressed in my reply to Double sharp concerning WP policy. For the record, I concur with 1, 2, 3, and 5. For #4 and #6 it certainly is significant given the LSPT literature's zeal about the regularity of the LSPT. It represents a case of significance by omission. --- Sandbh (talk) 06:53, 11 February 2024 (UTC)
 * @Sandbh: That the sequence of n is 1,2,2,3,3,4,4,… is obvious. But saying this is a LSPT flaw is not just describing, it is interpreting. Your interpretation, your opinion, is not shared by @Double sharp and I, nor, so far as you have shown, by any RS. Paraphrasing WP:RS, we do not publish the opinions … of Wikipedians who have … interpreted [facts] for themselves. Yes, the sky is blue, but to say that the blue sky is soothing or beautiful or ugly or whatever, you need RS. Let’s discuss this further when you find a RS.
 * ———- YBG (talk) 22:27, 11 February 2024 (UTC)
 * I agree with . Double sharp (talk) 12:08, 12 February 2024 (UTC)
 * Thanks. YBG, where you wrote, "But saying this is a LSPT flaw ", is ascribing something to me—that this is a "flaw"—that I have never written. That would certainly be an opinion or interpretation. OTOH, saying that the sequence 1,2,2,3,3,4,4,… is irregular, is obvious, in the same way that the sequence of n (as you put it) is 1,2,2,3,3,4,4,… is a statement of the obvious.
 * What's more, I've noted that mentioning the irregular sequence is accommodated within WP:CALC, WP:NOCITE; WP:PRIMARY; WP:BLUESKY and WP:NOTBLUESKY, and WP:COMMONSENSE.
 * The current situation is analogous to an unacknowledged elephant in the room, which is poor showing for an encyclopedia. Per WP:PRINCIPLE, Editors must also consider the rules in the broader context of the wiki editorial process and the goal of improving Wikipedia.
 * If it helps I would slightly change the footnote to refer to an "irregular sequence" rather than a "new irregulariy", as follows:
 * "That said, the left-step table has an irregular sequence, not present in the traditional form of periodic table, in that the progression of shell numbers at the start of each period is 1, 2, 2, 3, 3, 4, 4... i.e. the sequence is duplicated in all cases but the first."
 * --- Sandbh (talk) 01:36, 16 February 2024 (UTC)
 * If it were really so important as to be called an elephant in the room, then don't you think some RS would've mentioned it? Double sharp (talk) 14:23, 16 February 2024 (UTC)
 * Thanks. No, because the literature in this area is very limited and focuses on discussing the positive aspects of the LSPT e.g. that all elements in a period have an n+l value equal to the period number, unlike the conventional PT. Even so, this comes at the expense of irregularising the sequence of n numbers at the start of each period. It is like a game of Whac-a-mole. Fix one irregularity and another one pops up to take its place. This creates a gap in coverage, hence the expression, "unacknowledged elephant in the room". Addressing this gap aligns with Wikipedia's goal of creating a better encyclopedia. Sandbh (talk) 07:18, 19 February 2024 (UTC)
 * @Sandbh: In my previous post, I tried to demonstrate that this opinion (the irregularity in the sequence of n is a significant as a flaw in the LSPT). If you wish to comment on that from the WP policy angle, please reply to that thread.
 * In this thread, I would like to discuss not the WP angle, but the significance angle. I will do this by asking you to look at the conventional PT (CPT).
 * Let us examine the sequence of primary quantum numbers in the CPT. On the left side and the right side, this number increases regularly 1,2,3,4,…. It also increases regularly in each of the blocks (s,p,d,f,…). The CPT and LSPT share the right-side regularity and the per-block regularity, just not the left-side one.
 * However, one of the features of the CPT is that the leftmost and rightmost columns columns are full top-to-bottom with a gap in the middle. Let us consider the progression of n in the elements immediately before and immediately after CPT’s characteristic gap after opening the gap to make space for additional blocks f,g,h,….
 * To the left, we see a regular progression 1,2,3,4…. To the right, we see an irregular progression 1,2,2,3,3,4,4,….
 * Is this a significant irregularity in the CPT? No, it is simply an artifact of where the CPT places the stair step. And this is exactly why the same irregularity appears on the left side of the LSPT.
 * So the 1,2,2,3,3,… irregularity you noticed appears in both the LSPT and that CPT. The two tables simply position the irregularity differently.
 * As I said, if you wish to interact about WP policy, please respond to the other thread. If you wish to discuss the significance of the irregularity, respond to this thread.
 * ——— YBG (talk) 21:10, 10 February 2024 (UTC)
 * Thanks. This observation is irrelevant since the issue is only to do with the regularity of n values at the start of a period. In the CPT the sequence is 1, 2, 3, 4, 5, 6, 7. In the LSPT the sequence is 1, 2, 2, 3, 3, 4, 4. The LSPT thus introduces an irregularity not present in the CPT. FYI. --- Sandbh (talk) 05:17, 11 February 2024 (UTC)
 * Ok, I’ve failed to convince you. But it was worth a try, just as your unsuccessful attempt to convince me was worth the try. YBG (talk) 06:16, 11 February 2024 (UTC)
 * I've just posted a reply to Double sharp concerning WP policy. Sandbh (talk) 06:43, 11 February 2024 (UTC)
 * I've just posted a reply to Double sharp concerning WP policy. Sandbh (talk) 06:43, 11 February 2024 (UTC)