Talk:Lanthanide/Archive 1

Lanthanide compounds
I am the perverse character who wrote fairly lengthy articles on things like praseodymium(III) chloride, but I wanted to seek people's opinions on other compounds. I wrote a set of articles on most LnCl3 from Ce to Dy, and I still plan to do a couple of other chlorides, as well as some oxides such as Tb4O7. For major compounds like oxides & chlorides this seems worthwhile. However it would seem to be a big waste of time to write a separate page on each one of the 14 sulfates, each of the 14 nitrates, etc. I was thinking of writing a general page on lanthanide sulfates, one on lanthanide nitrates, etc. What do people think of this idea? What should such pages be called? And yes, I would include both La and Lu! Walkerma 16:35, 8 September 2005 (UTC)

what are lanthanides in
what are you talking about?! --feline1 11:26, 17 January 2006 (UTC)
 * This may relate to the group number. See discussion here, this explains why we omit the group no. from the individual element pages, though I note that Group 3 element does still include them.  Basically, IUPAC hasn't made a decision on this, until they do it's up in the air. Walkerma 15:26, 17 January 2006 (UTC)


 * well so what? what actual difference does it make to anything? it's just arbitrary nomenclature! Their chemical behaviour won't change no matter what "group" IUPAC decides to put them in!--feline1 15:46, 17 January 2006 (UTC)


 * Actually definitions do matter, 10 minutes ago I just happened to re-read a patent of mine, where it refers to the patent covering metals from group 3. We explicitly mentioned lanthanides, but if we hadn't, there could be a lawsuit over it!  More generally, students may get homework questions like, "List all of the group 3 elements."  Also, there is a space on every element page to indicate the group number, this is noticably absent now for lanthanides and actinides - it seems reasonable for someone to ask why. Walkerma 19:34, 17 January 2006 (UTC)


 * well lawyers will find ways to swindle you whatever nomenclature you use /yawns/ "Groups" are just conveniences of classification: nature and chemistry don't become more easy to understand just because the narrow-minded try and box it into inappropriate nomenclature schemes.--feline1 22:03, 17 January 2006 (UTC)


 * Nature and chemistry become incomprehensible without classification into scientific models. An encyclopedia cannot explain anything without defining its nomenclature. Narrow-minded is who does not arrange their knowledge. Femto 12:51, 18 January 2006 (UTC)


 * Look, Mendeleev decided to collect elements into groups because of similarities in their chemical behaviour. A "group" is not a "scientific model" (it does not seek to explain anything), it is just a handy bit of taxonomy. Some of the elements don't exhibit very strong group behaviour in the vertical direction and so it's seldom very useful talking about them like that... for other groups (eg alkali metals), it *is* very useful. Elements do not *have* to be "in a group"... the properties of the 14 lanthanoids are primarily down to their f electrons and so it is useful to think of them as a group (small g) on their own... it is not particularly useful to talk about them being in any of the 18 vertical Groups (big G) because none of those have f electrons - however, as we all know, Group 3 are their nearest cousins. You are all talking as if Groups are some sort of innate part of nature which elements have to "belong" to - but they're not, they're just a human idea to help keep things tidy, and some elements don't fit into them very well. Get over it!--feline1 14:24, 18 January 2006 (UTC)


 * I'd like to add, if this is an encyclopedia it should be accurate to the chemical world and what chemists use. We've had the same discussions in transition metal.  Yes it does matter!  You should not just put stuff in Wikipedia because you think your notiont is OK--it does matter to many of us.  Olin
 * […] --feline1 23:12, 6 February 2006 (UTC) -- Personal attack removed. No personal attacks. Femto 16:58, 9 February 2006 (UTC)


 * You are not an encyclopedic resource. If you can't use those qualifications to provide references showing that your point of view is neutral, derogative remarks won't convince anyone either. Femto 16:58, 9 February 2006 (UTC)

IUPAC recommendation
Why not move this page to Lanthanoid and redirect Lanthanide there instead?


 * I second that and suggest that Lanthanon also be redirected to Lanthanoid. Squideshi 04:08, 26 August 2007 (UTC)

Terminology - Promethium
There is an innaccurate statement in the section terminology. The article states that lanthanides are sometimes known as rare-earth (except for Promethium). However, Promethium is sometimes known as a rare earth as in webelements: [], in Brittanica [] and just about every other webpage found by conducting a google search. The problem here is in the definition of rare earth which is disputable, however this does not mean the article should be biased towards one particular definition as is currently the case in the article rare earth element. Polyamorph (talk) 22:01, 16 December 2007 (UTC)


 * That's right, even the IUPAC guidelines apply the term rare earths to "Sc, Y, and the lanthanoids" (and the lanthanoids explicitly include Pm). --Itub (talk) 12:19, 17 December 2007 (UTC)


 * I've removed the offending statement and also removed similar statements in the article rare earth element, see Talk:Rare earth element. Polyamorph (talk) 13:20, 17 December 2007 (UTC)

IUPAC convention for Periodic Table
IUPAC proposed a Periodic Table

http://www.iupac.org/reports/periodic_table/index.html

why not using this convention?


 * I changed the article (and actinide-article) to use IUPAC convention and to make it consistent with Wikipedia peridic table. --Levil 02:04, 23 August 2005 (UTC)


 * The convention should not have been changed without also changing the title and altering the redirect accordingly. Polyamorph (talk) 20:05, 22 January 2008 (UTC)

Didactics: Trication; Periodic Table Placement Basics
Boy, I thought I'd been around the block, but I've never heard the word "trication" and it has no Wikipedia entry, so I think it'll have to be defined or avoided here. You could use a simple expression and put (trication) in parentheses after it, to teach us newBs what the absolutely precise term is. Links between physics (atomic orbitals) and chemistry (triple bonds) might be fun to make, and would surely be helpful to others. Lanthanoid/Actinoid Periodic Table Placement ''"a Xenon-core electronic configuration with the addition of n 4f electrons, with n varying from 0 [for La(III)] to 14 [for Lu(III)]. This 4fn sub-shell lies inside the ion, shielded by the 5s2 and 5p6 closed sub-shells. " and, "Useful comparison can also be made with the actinoids, where the 5f shell is partially filled." '' As any of us who have had scientific careers in basic research know full well, there's a world of difference between the expertise and correctness needed to survive professionally (to do well in peer review for grants and papers) and the conceptual and cognitive skills needed to teach the intro course or create a successful textbook chapter. Speaking for myself, I come to the Lanthanoid page wanting to be reminded which shell gets filled and which is the shield(s) for the lanthanides and actinides. I need a compare-and-contrast: to what extent are we proceeding as in other periods of the periodic table, and in what ways do we see the effects of that shield? For a NewB, of course, the first question about the "series" in the phrase "lanthanide / actinide series" is why they are always presented specially in either conventional (short) or wide periodic tables. IMHO, at least a brief cruise past all of this belongs in the opening paragraph. Guys, I hate to do this, but can I be excused on the grounds that my Ph.D. is in psychology? This page is already up to a "B"rating, and I'd rather see the community take it to "A" than me drag it down. It is hardest of all to be simple but also correct. Life goes on, got to mow the lawn. --jerry P.S. Thanks for those (groan) mnemonics. Jerry-va (talk) 15:20, 31 May 2009 (UTC)


 * Hmmm, concerning "trication", it is in Wiktionary but not in Wikipedia. For one thing, it has nothing to do with triple bonds for one thing. Its use here, as well as the Wiktionary definition, suggests a triply positive charged ion, X3+, formed by removal of three electrons from a neutral species.
 * Interestingly enough, when looking up its doubly-charged analogue, I find a Wikipedia entry for dication, which wants dications to be "molecular species" having two electrons removed, and states that they often "decay quickly into two singly charged particles". This definition seems too narrow. Chemistry textbooks use dication also for polyatomic doubly-charged cations that do not exist as neutral molecules (e.g. Se102+, or why not the dimercury dication Hg22+ which certainly doesn't decompose into two Hg+ species). I think the author of dication was thinking specifically about diatomic examples from chemical bonding textbooks about molecular orbitals, forgetting that the term also includes stable species that have no neutral analogue.
 * I'm a bit confused, now, but it seems like the general notion is that dication is any double charged cation and trication is any triply charged cation (as in the wiktionary definitions), although in my experience the terms are most commonly used for cations consisting of more than one atom.
 * Adding to the confusion, some like to call cations or anions consisting of many atoms for polycations or polyanions, even though the charge could be 2 (e.g. in the english translation of the german inorganic chemistry book by Holleman/Wiberg, the authors use the word polyanion for Sen2-, although these should be called dianions according to the above definitions - and the original german version which I have doesn't even use this term polyanion. In fact, the sulphur analogs Sn2- are indeed called Dianionen in the original german book. Unfortunately Google Books omitted exactly those two pages so I could not check if the translators made the even bigger mistake there of translating Dianionen as polyanions, but I fear the worst...)
 * In my opinion, trication should not be used for single-atom cations, like the trivalent lanthanoid ions, because it suffices to say that they are trivalent cations. For polyatomic species, it is not that simple - e.g. mercury is monovalent in the dimercury dication. To conclude, I'll remove trication completely from this page.Beryllium-9 (talk) 11:36, 29 September 2009 (UTC)

Move Lanthanide to Lanthanoid
I propose moving the page Lanthanide to Lanthanoid in keeping with the recent move of Actinide to Actinoid Polyamorph (talk) 17:44, 29 April 2008 (UTC)


 * Done. IUPAC naming is pretty non-controversial. Checking redirects now. - Eldereft ~(s)talk~ 18:38, 29 April 2008 (UTC)

I'm not convinced "Lanthanoid" is actually the preponderant common usage. "Lanthanide" is still used in a great deal of literature. --JWB (talk) 19:46, 9 February 2010 (UTC)


 * It's the IUPAC numenclature, see here. Of course -ide was formally used and so it is going to be found in many textbooks but wikipedia should use the correct up to date IUPAC terminology. Polyamorph (talk) 20:07, 9 February 2010 (UTC)
 * I'm aware it is IUPAC nomenclature but judging from search results, it has not actually been adopted in common use. --JWB (talk) 20:43, 9 February 2010 (UTC)
 * Judging from google scholar then it doesn't seem to have been adopted in common use. However, it is the correct terminology and I expect it will just take time for academics to realise that a change has occured! I expect also (but this is just my personal speculation) that journals have their own standards for terminology and just simply haven't been updated. Polyamorph (talk) 20:59, 9 February 2010 (UTC)
 * I checked the policy in Naming conventions (chemistry). IUPAC terminology is preferred terminology in chemistry related articles. Polyamorph (talk) 21:43, 9 February 2010 (UTC)


 * See this community discussion. Polyamorph (talk) 07:28, 10 February 2010 (UTC)

Topic duplication with Rare earths
Discussion at Talk:Rare earth element on harmonizing these two articles. Please discuss there. - 2/0 (cont.) 18:10, 22 November 2010 (UTC)

First member of series??
Is lanthanum or cerium the first member of this series?? Georgia guy (talk) 19:18, 21 February 2010 (UTC)
 * It depends on who you ask. There are arguments on both sides. Lanthanum-138 (talk) 05:58, 5 June 2011 (UTC)
 * According to the definition in this article, the lanthanide series includes the 15 elements La to Lu. Lanthanum is therefore the first member of the series. However, as also explained in the article: "Strictly speaking, both lanthanum and lutetium have been labeled as group 3 elements, because they both have a single valence electron in the d shell. However, both elements are often included in any general discussion of the chemistry of the lanthanide elements." In which case cerium may well be described as the first element in the series. So really it's a personal preference, as long as you are clear of the convention you are using it shouldn't matter which element you decide to be the first. Polyamorph (talk) 08:07, 5 June 2011 (UTC)

If you use the (2 + 4 + 4 + 4) = 14 rule on this series you'll note immediately that the lopped off 71Lu Lutetium element doesn't fit into the series with it's physical properties as compared with the others.WFPM (talk) 16:58, 19 February 2012 (UTC) The Magnetic properties seem to be concentrated in the first 2 sets 0f 4, with the 5th element being unstable, the same as in the yttrium series.WFPM (talk) 19:10, 19 February 2012 (UTC)

Repetitious introduction?
In the introduction, the text below the table just seems to be a re-phrasing of the text above the table. I'm not sure a description of the different presentations of the periodic table is needed either, there is after-all a picture of it in the top right of the page - if needs be just have pictures of both versions. Project Osprey (talk) 12:56, 29 November 2012 (UTC)

Mnemonics
Do we really need a mnemonic device in the article, it doesn't really seem to have anything to do with the actual information of lanthanides. And IMO, its not that good of a mnemoic to begin with.--24.180.19.26 16:38, 10 January 2007 (UTC)
 * Mnemonics are common pedagogic devices used when teaching chemistry - by all means find a better one if that one is a bit rubbish.--feline1 18:01, 10 January 2007 (UTC)


 * It's also better to recognize that the sequential elements of the periodic table can be grouped and memorized in an easy mathematical sequence, which is, as per the Janet periodic table:

2 = 2                                                                                       2 =  2                                                                               2 + 4 + 2 =  8                                                                               2 + 4 + 2 =  8                                                                   2 + 4 + 4 + 2 + 4 + 2 = 18                                                                   2 + 4 + 4 + 2 + 4 + 2 = 18                                                   2 + 4 + 4 + 4 + 2 + 4 + 4 + 2 + 4 + 2 = 32                                                   2 + 4 + 4 + 4 + 2 + 4 + 4 + 2 + 4 + 2 = 32 For a total sequential element count of 120 elements! Which defines the number of elements in each group and makes it much easier to memorize the series of element names in sequences of 2 and 4 per group subsection.WFPM (talk) 03:31, 4 February 2013 (UTC)See Talk:Charles Janet.WFPM (talk) 03:35, 4 February 2013 (UTC)


 * Those who wonder what the significance of what the 2 values might stand for should note that the 2 values in the first 2 rows stand for the creation of an alpha particle within the nucleus.WFPM (talk) 22:37, 4 February 2013 (UTC)

article for expanding atomic properties sections?
Explaining Ln chemistry in terms of their electron configuration. Double sharp (talk) 11:01, 17 October 2013 (UTC)

Why is Ce4+ orange?
A colour cart of the various hexa-aqua complexes was added today and it made me wonder: Why is Ce4+ orange? It's electron configuration is basically a xenon shell, so there's no possibility of conventional phosphorescence. All I can think of is ligand-to-metal charge transfer... is that right? It's been nagging at me all day. Project Osprey (talk) 19:46, 10 October 2013 (UTC)
 * I got this from here, which refers to the orange solution as the "tetrapositive aqueous ion [of cerium] is formed". So it seems to be the real Ce4+ colour. I don't know why it has this colour (and was initially suspicious for the same reason), but Ce(SO4)2 has it too (and this was prepared by dissolving that compound in water.) CeO2, on the other hand, is colourless. I'm still not quite sure what's going on here.
 * (I'm not very happy with how the colours turned out all the time: Nd3+, Er3+, and Tm3+ are a bit too dark. I have never seen the Pm3+ colour anywhere and so it is a guess based on the description and the appearance of salts like Pm(NO3)3 and PmF3. I haven't seen either, but the former is stated to look very much like its neodymium analogue. Eu3+ and Tb3+ are really even closer to being colourless than what you see here. Still, it's an approximation.) Double sharp (talk) 06:11, 11 October 2013 (UTC)
 * I'd be surpised to meet anyone who's seen Pm first hand. I have to say though, I was surpised to learn that Eu3+ is pink, it's normally famed for its green colour - although I admit my training focused more on their phosphorescence. However it still implies that some of these colours aren't being caused by simple f-f transitions. If you have access to it I'd recomend 'Chemistry of the f-Block Elements' by Helen Aspinall, its beyond my reach now but it's a good general guide. Project Osprey (talk) 09:28, 13 October 2013 (UTC)
 * My understanding from memory of Ce(IV) oxide glasses was that the colours were due to charge transfer complexes. The aqua ion according to Simon Cotton is thermodynamically unstable and the difference in redox potential in different oxo acids indicates "complexes rather than a simple aqua ion". The clincher would be anion dependance of aqueous spectra so other examples of Ce(IV) solution colors would be useful, as sulfate and nitrate are similar. Axiosaurus (talk) 17:25, 15 November 2013 (UTC) In The Rare Earth Elements: Fundamentals and Applications edited by David A. Atwood it says that the beta-diketonate complexes are purple as are the hexabromocerates. And found a reference to CT spectra in oxides- J. Inorg Nucl chem 1975, 37, 1917-1921 CT spectra of tetravalent Lanthanide ions in oxides, by Hoefdrad. Axiosaurus (talk) 19:55, 15 November 2013 (UTC)
 * My issue here is whether its WP:UNDUE. One might reasonably expect the colours of the aqua-ions to be the colours of the metal ions themselves (i.e. the f-f transitions) but this is clearly not the case: the f-f transition for Eu3+ is red, Ce4+ should be colourless. So these colours are (at least to some extent) unique to water. This raises the question of why these colours are important; why not the colours in ammonia or EDTA? Personally I think a table of their f-f transitions would be more suitable, as they are an intrinsic property, but I'm open to counter-arguments. Project Osprey (talk) 11:24, 16 November 2013 (UTC)
 * Aqueous solution is relatively common, and Greenwood & Earnshaw feels the need to list them (I don't think it lists the colours for other solvents). So I think they should stay. (Of course, I'm the one who added them in the first place.... ;-P) Double sharp (talk) 15:51, 17 November 2013 (UTC)
 * Personally I like the color section, but the colors are too bright. As taught IMHO the t metal color story is over-egged making them sound unique, which isn't the case. As an aside f-f transitions - the LS coupling rationale is difficult to get over I wouldn't like the question "f orbitals are degenerate aren't they, just like d so what is splitting them?" and then the follow up OK, well why doesn't LS coupling affect T metals?- looking at the article perhaps the reason isn't pushed hard enough- I'm thinking about that one. Regarding Ce(IV), if included, it needs a reason why it is colored, again I would keep it, but it needs an explanation and a decent reference for c-transfer. Regarding Eu3+ - weak forbidden f-f transitions are to blame- which of couse points to phosphorescence as a possibility. In phosphorescence the transition is from the excited 5D0 -> ground state and near ground state levels, 7F0,1,2,3,4, again the article doesn't quite push the point about forbidden transitions / phosphorescence etc enough and there are no linkable articles I can find- Angular momentum coupling which mentions LS coupling - is a typical physics article - pretty useless for chemistry students. Any way I would add a little color chart or photos for preference of phophorescent colors. Axiosaurus (talk) 18:20, 17 November 2013 (UTC)

New sections
I have added a short secion on the hydrides. I have other sections I am working on- albeit slowly. I will be adding these when complete. Axiosaurus (talk) 09:36, 18 February 2014 (UTC)

Couple of quick queries: Do the hydrides form under ambient conditions? Do they have any notable uses?
 * Gentle heating (300-350 C)/ 1 atmos' pressure for the dihydrides - less than that for TiH2 for example. no notable uses - but some hype about the  possibility of switchable mirrors for Mg doped Ln trihydrides- thin film LnH2-LnH3 transition turns reflecting to clear.
 * Depending on how much you eventually add I might have a go at reorganising the page; it's becoming a little... dendritic. Project Osprey (talk) 11:28, 18 February 2014 (UTC)
 * Hold off a while with the "pruning/topiary" I will be adding quite a bit which will change the shape of the tree. Axiosaurus (talk) 14:46, 18 February 2014 (UTC)


 * Would it be instructive to use the Ln's part of Periodic table (electron configuration)? In there I can follow the filling-sequence (+jumps). Another list, in f-block, is less easy to follow. I could make the cutout, if you want use it. -DePiep (talk) 14:06, 19 February 2014 (UTC)
 * Hey thats nice! I hadn't seen that before. Part of the problem with lanthanides, as with t. metals, is that the aufbau principle predicts orbital occupancy of the ground state but not the sequence in terms of energy. There's the possibility of config. crossover, caused by the atomic environment, to contend with as well. I haven't added got to writing that bit yet, but I will bear the graphic in mind. Axiosaurus (talk) 12:23, 20 February 2014 (UTC)
 * OK. I'll start making that Ln graph. It's just that I am buzy in RL this month. When we have more space because they are 15 elements only, we could develop a more elaborate graph (and more explaining). That way I will understand it better, too ;-) More later, here. -DePiep (talk) 13:56, 20 February 2014 (UTC)
 * See Periodic table (electron configuration lanthanides). A first throw.
 * Ask, edit, and cut out stuff ask as you like. IMO it could use more attention for the actual shells. Keep the talk here, I suggest. DePiep (talk) 16:04, 20 February 2014 (UTC)


 * In a somewhat related note, would any of cells here be useful? We'd have to link to them, obviously, but they're very visual. (I suppose I should declare WP:POTENTIALCOI here, as I have an indirect association with the work). Project Osprey (talk) 19:39, 22 February 2014 (UTC)

Lanthanide vs. f-block
Should this sentence be removed: "Another name for the lanthanides and actinides is the f-block, and in the case of the lanthanides it is the 4f orbitals that are being filled." F-block has 14 elements in one period, where lanthanides have 15 (per description on the page). Also, Lu has a full 4f orbital (as Yb), and adds one electron to 5d orbital (as such not really filling the 4f orbital, but rather starts filling 5d orbital). --67.164.60.31 (talk) 06:08, 17 June 2014 (UTC)
 * I corrected it to "All but two of the lanthanides and actinides are f-block elements (the exceptions being the lanthanide lutetium and the actinide lawrencium), and in the case of the lanthanides it is the 4f orbitals that are being filled." By the IUPAC definition of the terms lanthanide and actinide, Lu is a lanthanide and Lr is an actinide, although neither are f-block elements. Double sharp (talk) 07:17, 17 June 2014 (UTC)


 * Thank you. The first clause is correct right now.  But, wouldn't the sentence 'All but 28 lanthanides and actinides are d-block elements (the exception ...) be also valid?  Are we buying anything by including this sentence here?
 * Although IMO the new second clause is not true due to Lu.
 * To me, this whole sentence is trying to support one of the the old points of view (before IUPAC definition of lanthanides - sans Lu), and adds not necessary exception to maintain the truthfulness. IMO, the f-block is a group based on physical properties, the lanthanides is a convenience group based on how they fit (don't fit) into the short periodic table (yes, there are chemical / physical similarities, but if you include Hf in the group, you can still try to justify lanthanides name, as there is not that much difference between Lu and Hf, etc).  Therefore, I would still suggest that the sentence be removed. --67.164.60.31 (talk) 14:10, 17 June 2014 (UTC)


 * One more thing. The first sentence and the whole section look like:
 * "Some of the lanthanides belong to 6th period, f-block elements. The effect of f orbitals on the chemistry of the 6th period, f-block elements ..."
 * You see, this section is not really talking about the lanthanides, but rather 6th period, f-block (6P-fB) elements (group that doesn't have a nice short name). The first sentence is trying to find a bridge between the lanthanides and 6P-fB elements, to justify a nice description of 6P-fB elements.  Maybe, if that section is moved to f-block, it would perfectly serve the f-block info, and would not be that much offending being here?  IMO, talking about 6P-fB group, and mentioning that some lanthanides are in that group sounds reasonable, on the other hand, talking about lanthanides, and making various exceptions to justify description of 6P-fB doesn't sound reasonable at all.  --173.13.184.74 (talk) 16:25, 17 June 2014 (UTC)
 * It's more important to talk about the f-block than the d-block here simply because it's the f electrons that play a major role in lanthanide chemistry. Even when they are not involved in bonding, they give rise to many magnetic effects, and result in the lanthanide contraction (which extends to Lu).
 * There is a big difference between Lu and Hf – Lu tends to be oxidized to the +3 state, while Hf tends to be oxidized to the 4+ state (and Hf(III) is not stable).
 * It's not just Lu which is an exception: La and Gd are also exceptions, as they add a 5d electron from the previous element. Maybe it is better to think of the electron configuration in the leaving order, but then all of them give up 6s2 first and then 4f1 or 4f2 (except La, Ce, Gd, and Lu, which use 5d1 before 4f1, if the latter ionizes at all).
 * The thing is, talking about the 6th period f-block elements cuts Lu out, although it fits chemically with the series; but the f-electrons give the lanthanides their distinctive chemical and physical character (including La, Ce, Gd, and Lu). As it stands the statement is strictly speaking still not correct without Lu. So I changed the whole sentence to just "Going across the lanthanides in the periodic table, the 4f orbitals are usually being filled.", which is true and still quite relevant. Double sharp (talk) 02:56, 19 June 2014 (UTC)


 * Thank you, appreciate your explanation. Also, the change in text is quite nice. --50.168.49.29 (talk) 05:27, 2 July 2014 (UTC)
 * Oh, and one more thing: if we are talking about "before IUPAC", I doubt Lu was ever excluded from the lanthanides since Jensen's famous paper arguing for Lu to be placed under Y was published in 1982. In fact I think La was the one usually excluded from the lanthanides: indeed Greenwood and Earnshaw similarly states that Ac's position as an actinide is equivocal in their 2nd edition, and exclude it from their chapter on the actinides while simultaneously acknowledging that it is useful to compare it with the other actinides. If you think about it, this makes some etymological sense, as both "lanthanide" and "lanthanoid" (I think) convey the idea that the elements the term refers to are similar to lanthanum. But La is not similar to lanthanum: it is exactly lanthanum! Of course, words aren't defined etymologically all the time, so La can stay as a lanthanide and Ac can stay as an actinide per IUPAC's usage. Double sharp (talk) 21:08, 3 August 2014 (UTC)

Shell filling overview
Some time ago I started table to show the shell filling of Ln and especially the jumping numbers (Madelung rule breaches). To me at elast it looked more clarifying than the more textual table. Would this table improve the article? Information can be added or improved of course. If this setup is acceptable, actinides can get one too. -DePiep (talk) 10:50, 24 August 2014 (UTC)

Organometallics
I removed from article: "Similarly complexes of cyclopentadienyl anion (Cp−), e.g. [Ln(C5H5)3], are far less common than the corresponding pentamethylcyclopentadienyl, e.g. [Ln(C5Me5)3Cl]." This makes little sense. CP3LN were some of the first metallocene creates (only 4 years after ferrocene p112) They have been widely studied. I think the intention may have been to indicate that it is easier to make compounds with ligands larger than Cp, like Cp* and a previously mentioned Si version, because of the f-orbitals. However there is no source for the claim and Cp* compounds of transition metals (d-orbitals) are not rare. Rmhermen (talk) 05:33, 16 December 2015 (UTC)

regarding recent edits
It is actually rather common in inorganic chemistry texts (e.g. Greenwood, Holleman) to say that there are only fourteen lanthanides (Ce to Lu) and to include La, like Sc and Y, only for comparison. Part of it is semantics (it is argued that 'lanthanide' means 'lanthanum-like' and thus must exclude La itself) and part of it is a desire to categorise La as the third member of group 3 and thus a transition metal, if a rather equivocal one. Does it go against IUPAC? Oh yes, certainly. But I think it is worth mentioning. (I have not seen the analogous Lu-excluding definition from Sc/Y/Lu/Lr proponents, so I would not mention that one.) Double sharp (talk) 08:56, 11 September 2016 (UTC)
 * I wondered about that when I reverted the edit. But even so, I still would have reverted as the edit made was inconsistent in changing the atomic number range without changing the total count (fifteen). Feel free to change it to whatever is best, but just make sure that the atomic number range agrees with the count listed. YBG (talk) 00:36, 12 September 2016 (UTC)
 * I added a sentence to the lede saying "La is not always included as a lanthanide." Double sharp (talk) 01:23, 12 September 2016 (UTC)

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 * Added archive https://web.archive.org/web/20080415085514/http://www.chem.unr.edu/faculty/abd/ to http://www.chem.unr.edu/faculty/abd/

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Move discussion in progress
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