Talk:Extended periodic table

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Location of the 6f series[edit]

According to predictions, the whole set of the elements 121-156 has their 6f subshell available for chemical bonding, and it is quite difficult to exactly locate the 6f series. But we may look at the earlier periods: 5d electrons appear in La and Ce, way before the 5d series; 6d subshell is populated in many actinides; 7p electron is active in lawrencium before p-block. So we see that p, d and f-blocks correspond to the valence subshells with highest angular momentum, with possible exceptions for Zn and Cd. Indeed: Ac and Th use their 5f, 6d, 7s and probably 7p subshells, which make them members of f-block, while Lr use only 6d, 7s and 7p and is a member of d-block.
Looking at the configurations of elements 121-172 predicted by various authors, we may notice which subshells are probably valence either as highest occupied (HO) or as lowest unoccupied (LU):

  • elements 121-142 use 5g, 6f, 7d, 8s, 8p1/2 subshells as HO or LU, so they might belong to g-block;
  • elements 143-156 use 6f, 7d, 8p1/2 subshells as HO and maybe 9s as LU, so they might belong to f-block;
  • elements 157-166 use 7d and 9s subshells as HO and 9p1/2+8p3/2 as LU, so they might belong to d-block;
  • elements 167-172 use 9s and 9p1/2+8p3/2 as HO, so they might belong to p-block.

The most arguable thing is the precision of these bounds. 7d-series, from 157 to 166, is discussed in the previous section; let's now concentrate on the bounds for 6f series.

Pekka Pyykkö's computations show that element 142 is the last one where 5g and 8s subshells are still open for chemical bonding. Although the neutral atoms of elements 143 and 144 has probably still unfinished 5g-subshell, it become 5g18 when atom is positively ionized (the reason was mentioned in the previous section: subshells with higher angular momentum are drowned deeper because of less screening). On the other hand, positive charge is the only way to reach 5g orbitals for (at least indirect) chemical bonding because of their small size. Therefore, element 142 is a good candidate for the end of g-block.
So, 6f series is probably started at element 143 since its 6f subshell has the highest angular momentum among valence subshells 6f, 7d and 8p1/2. As for the right end of the 6f series, most of the authors agree that 6f become filled near element 156. Pekka Pyykkö shows that triple cation of element 155 has 6f14 and still may be chemically ionized further (the calculated ionization potential for Upp3+ is higher than for Tb3+, but lower than for Dy3+). Other authors predict a bit higher energy of 6f subshell in the vicinity of Z=156, but all of them agree that for Z=158 the 6f subshell is buried deep down together with 8p1/2.
Taking all of this into account, it might be possible to formally assign:

  • elements 121-142 to g-block (although 5g is empty for a few first elements, it is used as lowest unoccupied subshell, just like 5f for Ac and Th);
  • elements 143-156 to f-block (although we need more accurate predictions to see a tight deadline where 5g subshell becomes inactive);
  • elements 157-166 to d-block (although 7d subshell is probably inactive in element 166, that's the very case for zinc (3d) and cadmium (4d), so the analogy resists);
  • elements 167-172 to p-block (although there's no pure 8p subshell, a hybrid 9p1/2+8p3/2 will go well for 8th period).

But then we should certainly make a warning that this is only a rough pattern, while the real chemistry of these elements is far deeper, and now we have no calculations precise enough to make more detailed arrangement of elements in 8th period. Droog Andrey (talk) 15:17, 8 March 2016 (UTC)

That's how it will look like.
I support this. You make a lot of sense and argue based on many reliable sources. (I'll need to rewrite the part about 165 and 166 to make it clear that they are probably going to be closer to IB and IIB than to IA and IIA, though that does not, of course, bar them from having some characteristics of the latter.) Like you, I don't think we can say any more till more theoretical studies appear, or we synthesise all the period 8 elements till 172 (and I am very doubtful that either of us will live to see that). Double sharp (talk) 15:33, 8 March 2016 (UTC)
(I really like this development. Looks great). -DePiep (talk) 20:51, 11 March 2016 (UTC)
I can't see the far left of that image; there's no scroll option. This image is just like simple extrapolation except that the g-block has 22 elements instead of 18. Any corrections to what I'm saying?? Do 4 of the 22 elements in the 121-142 interval belong to a special block?? Georgia guy (talk) 21:03, 11 March 2016 (UTC)
(Just click the image, and you arrive at the image view for a complete viewing). It's not a simple extrapolation. It is a careful and helpful representation of the sources. It really helps the average Reader (trust me). -DePiep (talk) 21:25, 11 March 2016 (UTC)
The main comment I have is that I support that, in an appropriate position, this article needs an image of the periodic table made by simply extrapolating the periodic table. Yes, the article has a message saying "Although simple extrapolation..." for clarification on what it would be. Georgia guy (talk) 21:32, 11 March 2016 (UTC)
I don't get what you mean, because I only can talk about the graphics (including the horizontal scrolling option; it'll be allright in any article for sure). For the textuals like Although simple extrapolation... (sure that is a bad article approach!), I leave that to other editors here on this talkpage. -DePiep (talk) 22:07, 11 March 2016 (UTC)
(I'm very, very interested where this conversation between Droog Andrey and Double sharp leads to. Will be a great article improvement, also into Readers' like me understanding (that is: clarifying). Now back to the main topic.) -DePiep (talk) 23:17, 11 March 2016 (UTC)
A periodic table by "simple extrapolation" would look exactly the same, but would end the g-block at 138 instead of 142. (So, for example, 168 would be under 118 instead of 172.) Double sharp (talk) 09:36, 12 March 2016 (UTC)
Let's make a difference between "simple extrapolation" and "extrapolation of Madelung's rule". The variant with element 168 in the VIIIA group is just a meaningless venture to pull the Madelung's rule beyond 7th period where it doesn't work because of progressive relativistic effects. The variant I proposed is indeed a simple extrapolation, but it is overall supported by rough quantum-chemical calculations. To ensure any more detailed arrangement of the elements (say, to prove some explicit bounds on some special series and so on), we should wait for some deep calculations of atomic and molecular species with at least MRCI level of theory with high-order relativistic hamiltonian. Droog Andrey (talk) 23:45, 13 March 2016 (UTC)
You're right, of course, but your extrapolation is not really conceptually simple. It looks simple, but you can only get to it via relativity, so perhaps it could be stated to be based on a more detailed, relativistic look at the situation. Meanwhile, we could clarify the wrongness of the Aufbau extrapolation by calling it a naïve extrapolation. Double sharp (talk) 15:20, 14 March 2016 (UTC)
Sounds good to me. Droog Andrey (talk) 20:12, 14 March 2016 (UTC)

I reread Fricke's paper, and even he (what with his placement of 164 under Hg and Cn) says it is most analogous to group VIII (= 10). In fact, he writes in Table 6 that 157 should be most similar to group IIIB, 158 to group IVB, and so on. As for 165 and 166, Fricke puts them in IA and IIA, citing predicted ionisation energies which fit the trend in these groups better than those in IB and IIB. But he also admits that 7d will be active chemically, which is unlike the behaviour of IA and IIA, because it is easier to penetrate a filled d10 shell than a filled p6 shell. Since chemical properties form the basis of this whole extrapolation, I think we really should change this to the format proposed above.

Double sharp (talk) 14:50, 2 August 2016 (UTC)

P.S. Regarding 167–171; I cannot imagine an element with such density being a nonmetal or metalloid, and I only mark 171 as such for its chemistry. Double sharp (talk) 15:02, 2 August 2016 (UTC)
That looks very good. Droog Andrey (talk) 21:27, 13 September 2016 (UTC)
All right, I've made the changes!
I should note that we are considering moving group 12 to the post-transition metals. Element 166 would be similarly affected since it is much less sure if 7d10 will be active there than at element 165. Double sharp (talk) 01:44, 13 October 2016 (UTC)
This categorization violates WP:OR. --Abelium (talk) 17:03, 14 October 2016 (UTC)
  • elements 157-164 to d-block
  • elements 165-176 to s-block
  • elements 167-172 to p-block (although there's no pure 8p subshell, a hybrid 9p1/2+8p3/2 will go well for 8th period).
I propose this categorization. --Abelium (talk) 17:03, 14 October 2016 (UTC)
No it is not OR. Paper. Double sharp (talk) 02:23, 15 October 2016 (UTC)
Furthermore, even Fricke's original paper assigns element 157 to the "chemically most analogous group" IIIB, all the way to 164 at VIII. Even though he places 165 and 166 as close to IA and IIA, he also notes that they would have substantial similarities to IB and IIB. OR? I think not, when even the papers being cited equivocate on exactly which groups these elements are in, and it was pretty easy to find a paper giving the current classification. And I can see you haven't actually read the whole discussion, or even looked at the papers involved, or else you would have noticed this. Double sharp (talk) 02:25, 15 October 2016 (UTC)
This paper did not explicitly mention about E165-172. Furthermore, E164 and E163 are very dense elements, but E165 and E166 are not. Chemical consensus is E165-E172 are Period 9 elements. --Abelium (talk) 08:58, 15 October 2016 (UTC)
Your last sentence is demonstrably false: Pyykkö's paper certainly places E169–E172 in period 8. Leaving aside that the density estimates are first approximations only, I'm not particularly surprised that the density falls down after the 7d-shell finishes filling. Remember that 9s has only just fallen down to be permanently energetically favourable to occupy (this must be a close thing, because the earliest Fricke calculations don't predict 9s involvement in E156–164), and there is a great deal more stuff in the core than usual (instead of adding 5f shielding in period 7 at Rg, we now have shielding by 5g, 6f, 8s, and 8p1/2). That the 9s electron would then be really far from the nucleus is therefore not unexpected in E165 and E166 – but even according to Fricke et al., 7d has not sunk into the core yet at E165.
Furthermore, we seem to agree that E167–E172 are members of groups IIIA to 0. If E164 is in VIII, and E167 is in IIIA, there is an unsightly gap that could be easily filled if E165 and E166 were members of groups IB and IIB. And, lo and behold, look what Fricke et al. write: "From the normal continuation of the periodic table one would expect that after the completion of a d shell (at element 164) two elements in the IB and IIB chemical groups should appear. In a very formal way this is true, because with the filling of the 9s electrons in elements 165 and 166 there are outer s electrons chemically available." They then admit that this has some problems because these are not the same 8s electrons that began the period way back at E119, and that they also show some characteristics of IA and IIA because 9s is further from the nucleus than would be expected (see what I wrote in the previous paragraph). But, and this is the key point, Fricke et al. note that they would still be transition metals. Thus they write "This classification [of E165 and E166 as members of groups IA and IIA] is, of course, not entirely, satisfactory in every respect because from a more chemical point of view these elements will also show characteristics of the IB and IIB groups because of the underlying 7d shell. Therefore, higher oxidation states than +1 and +2 might readily occur." That settles it IMHO, as Greenwood and Earnshaw wrote: "the first ionization energies of the [group IB elements] are much higher, and their ionic radii smaller than those of the corresponding alkali metals. They consequently have higher mps, are harder, denser, less reactive, less soluble in liquid ammonia, and their compounds more covalent...a filled d shell is more easily disrupted than a filled p shell...they are able to adopt oxidation states higher than +1. In short, Cu, Ag and Au are transition metals whereas the alkali metals are not." Indeed, comparing E165 with E119, the previous alkali metal, we see a higher (though not as high as usual because 9s is a little further than usual) ionisation energy, a smaller atomic radius, almost double the density, and a willingness to breach the inner 7d subshell. This is clearly transition-metal behaviour, chemically. At the very most you could have E165 like silver, preferably forming the +1 oxidation state but still allowing the shell to be breached (as well, look at how Ag falls down in density from the previous elements as 4d sinks almost into the core, and how the group 12 elements fall down even more). Double sharp (talk) 11:48, 15 October 2016 (UTC)
Lastly, despite Fricke et al. daring to call E119 and E120 "alkali" and "alkali earth", they do not do so in the table for E165 and E166, contenting themselves with "IA" and "IIA" (and implying "IB" and "IIB" in the text). Double sharp (talk) 12:44, 15 October 2016 (UTC)
Just preventing from falling into archive. Droog Andrey (talk) 23:27, 14 October 2017 (UTC)

Walter Loveland quote[edit]

"Does the Periodic Table have limits? YES!! At some point (Z~122) all the electron energy levels of adjacent elements are similar so that there are no differences in their chemical behaviour." (source).

This is the explanation of Droog Andrey's initial colouring of all the superactinides as one group, without breaking it into a g- and an f-block: it gets very difficult to break things into separate "blocks" past Z = 122, because 5g, 6f, and 8p1/2 are all mixing and are very close to each other; 7d is somewhat further, so we still get a reasonable transition series ending at Z = 166. (It is rather convenient that a "second island of stability" is expected to surface around Z = 164, right as we get out of the woods of the superactinides, so that the elements which we will be able to chemically investigate first will be the ones that make increasingly more sense in terms of what we already know in the first seven periods, until we reach eka-oganesson at Z = 172 in the next century.) Even the current colouring of "blocks" is rather formal and doesn't quite correspond to what we normally think of as the blocks: for instance, the g-block is shown with twenty-two columns, although there is only room for eighteen electrons in the 5g shell. It's almost as if the h-block, sad that it was never going to get filled up before weird things started happening at Z = 173, decided to infiltrate the g-block and make it have its characteristic twenty-two instead of eighteen columns. ^_^ More seriously, the lack of distinct chemical behaviour between elements filling the g-, f-, and p-orbitals in this region shows what Loveland is referring to here as the limits of periodicity.

It is still worth noting that all the extrapolations I am aware of past Z = 122 are incomplete in one way or another, so that these shores are largely still unexplored. But it is still useful to have a map to guide us as far as it can, even if between Z = 122 and Z = 157 it says "here be dragons"! ^_^ Double sharp (talk) 16:03, 29 March 2017 (UTC)

Aufbau variant[edit]

What's the point to place it into the article? https://en.wikipedia.org/wiki/Extended_periodic_table#Extended_periodic_table Droog Andrey (talk) 11:23, 4 February 2018 (UTC)

I could see reason for placing it in a "History" section, as it was the original one Seaborg suggested. I do agree though that this is not the best spot for it. Double sharp (talk) 11:38, 4 February 2018 (UTC)

Interesting remark on element 173 (which may well be considered a good alkali metal)[edit]

From primefan.ru: "Однако для Z > 155 обнаруживается весьма интересное стечение обстоятельств: сближаются по энергии 7d- и 9s-подслои, а затем 8p3/2 и 9p1/2, после которых образуется большой энергетический зазор. ... По всей вероятности, туннельные эффекты не позволят существовать атомам элемента №173 продолжительное по химическим масштабам время, даже если будут получены его относительно стабильные по отношению к ядерному распаду изотопы (что само по себе крайне маловероятно). Расчеты при этом указывают на то, что единственный валентный электрон этого элемента будет находиться на 6g-подслое и иметь столь высокую энергию, что цезий по сравнению со 173-м можно будет считать металлом невысокой активности." (Attempt at translation forthcoming tomorrow; I'm out of time today.) Double sharp (talk) 15:41, 21 February 2018 (UTC)

Please translate that into English. Georgia guy (talk) 15:44, 21 February 2018 (UTC)
This means: "However, for Z>155 there is evidence for quite an interesting combination of circumstances: 7d and 9s subshells are close in energy, and so are 8p3/2 and 9p1/2, after which there is a large energetic gap. ... In all probability, tunnel effects do not allow element 173 to exist for a time enough for chemical investigation, even if its relatively stable towards nuclear decay isotopes will be synthesized (which is by itself highly improbable). Meanwhile, calculations indicate that the only valence electron of this element belongs to the 6g subshell and its energy will be so large that caesium when compared to 173 may be considered a metal of low activity." Burzuchius (talk) 20:44, 21 February 2018 (UTC)
That's my old popular-science article for high schoolers. Since then I realized that Z > 173 is really not a problem (see below).Droog Andrey (talk) 21:06, 24 February 2018 (UTC)

Elements 173 and 174[edit]

Just recently, Double sharp made an edit saying that element 173 is expected to be an alkali metal. If this is true and creating element 173 is possible, then creating element 174 should be just as difficult, assuming it's the corresponding alkaline earth metal. Any flaw?? (In determining what to say on this section of the talk page, please include your opinions on whether each of element 173 and 174 should be included on the table of elements in this article that Double sharp recently added element 173 to as an alkali metal.) Georgia guy (talk) 00:19, 22 February 2018 (UTC)

It's not entirely clear what exactly happens once you pass Z = 173 and the 1s electrons dive into the negative continuum, but whatever does happen may not allow such atoms to stick around long enough to be considered elements. In other words, though 173 may or may not give problems, from 174 onwards there are likely to be problems, and things are expected to be different enough that we cannot promise anything. Besides, I don't see predictions about element 174 in any reliable source yet, so 173 should be in and 174 should be out. This sort of stability is rather divorced from what happens to be in the outer shells.
As for the chemistry: remember that the 6g, 7f, and 8d shells are expected to be of rather similar energy and all really quite a lot higher up than the shells filled up in the [E172] core; E184 should have some of each. Thus I am inclined to think that early expectations of very high oxidation states for such elements would turn out to be roughly on the mark. It seems likely that a comparison of E184, like Fricke gives, to U and Np is plausible: it would likely be an electropositive metal (perhaps more so than the actinides) showing variable oxidation states, as expected since the 6g orbitals have radial nodes that are absent in the 5g orbitals. The 10s and 10p1/2 orbitals may also join in the fun later, though I'm sceptical about 6h (Fricke gives 5h, but this is clearly a mistake) due to its high angular momentum. Double sharp (talk) 01:19, 22 February 2018 (UTC)
BTW it should also be noted that the difficulty of creating eka-francium and eka-radium should vary significantly with the target–projectile reaction that is being used (the more asymmetric the better). As for dvi-francium and dvi-radium (assuming that it's not a problem for the 1s shell to dive into the negative continuum), we should also remember that target–projectile reactions are highly suspect as a way to reach elements on the second island. If you accelerate uranium ions at a uranium target you can hardly expect to make any atoms of element 184. At the most you might have a transfer reaction and make an early period 8 element, but hardly a late period 8 element. When we gain the technology to probe the region around the magic number 164, I suspect that different methods will be in use (although I am not sure either of us will live to see it), and I am quite sure that they will show just as much if not more variability. Double sharp (talk) 05:10, 22 February 2018 (UTC)
AFAIK, there's no problem with negative continuum for Z > 173 except for some issues about positron scattering. There's a good article on this (sorry, in Russian). Droog Andrey (talk) 20:56, 24 February 2018 (UTC)
@Droog Andrey: Very interesting (and I'm sorry that I can't understand it). Does the article at least give a summary on what happens once the 1s subshell dives into the negative continuum? Is it anything like what Joachim Reinhardt and Walter Greiner say in this article? I'll give a few quotes:
The electric field strength at the surface of a nucleus exceeds Ecr [= πm2c3/] by about three orders of magnitude. Nevertheless in ordinary atoms pair creation does not occur because the created electron quantum mechanically would not fit into the narrow well of the Coulomb potential. This changes when atomic structure is extrapolated from the known region of chemical elements by about a factor of two. As discussed above, supercriticality sets in at Zcr ≃ 172 when the 1s1/2 state "dives into the lower continuum" and is transformed into a resonance.

In the language of Dirac's hole picture, if an empty bound state enters the lower continuum it will get filled by a sea electron which can tunnel through the classically forbidden gap of the Dirac equation, leaving behind a hole, i.e., a positively charged positron, which escapes to infinity. This is just an instance of the Schwinger mechanism for pair creation. The process also has been termed "spontaneous pair creation" or "decay of the vacuum" of QED. The difference to Schwinger pair creation in a constant electric field is that in supercritical atoms the strong field is confined to a small region in space which can harbour only a small number of created electrons. I.e., pair creation is stopped by "Pauli blocking" when the available electron states are occupied. In a weakly supercritical atom (172 < Z < 185) just two positrons (spin degeneracy) can be produced in this way.

In a world with a fine structure constant α somewhat larger than our physically realized value supercritical atoms would be an everyday phenomenon. It would be impossible to fully ionize heavy atoms since their inner shells would be filled by "electron capture from the vacuum" (bound-free pair creation). The supercritical atoms would exhibit narrow resonances in the scattering of positrons.

I notice that they cite as their reference [4] a paper also by Zel'dovich and Popov, though dated 1972 rather than the 1971 of your article. This would seem to mean that there is no problem other than the limitations of nuclear stability, even as 1s1/2 dives into the negative continuum around Z = 170 and 2p1/2 and 2s1/2 around 185 and 245 respectively. (It looks like I'll have to rewrite this piece again to take this into account.) Double sharp (talk) 14:06, 25 February 2018 (UTC)
P.S. Their reference [3] has doi 10.1007/BF01398198, and the following chapter in Nuclear Physics: Present and Future also contains some information on experimental probing of this supercritical region. It really does look like I will have to rewrite some of the later sections again: what a shame it is that I can't find any chemical predictions on the ninth period past its opening at E173 and the glimpse of the "eka-superactinides" at E184! Double sharp (talk) 14:53, 25 February 2018 (UTC)
That's the same article. It was probably translated to English in 1972. There's a short quote from it:
4.4. До сих пор мы рассматривали голые ядра. Если же уровень 1S занят электронами, то при переходе через Ζ = Zc никаких видимых эффектов не возникает. Электронное облако, несущее заряд —2е, образуется при Ζ < Zc двумя электронами на нижнем (дискретном) уровне, а при Z > Zc — возмущением функций континуума вблизи энергии ε = ε0 < —1. Если проинтегрировать плотность зарядов по всему непрерывному спектру, то при Ζ > Zc получится (после перенормировки) как раз лишний заряд —2е. Хотя формально K-оболочка при Ζ > Zc исчезла (из одночастичных решений уравнения Дирака), но ее роль берет на себя сплошной спектр. Поэтому, например, электроны внешних оболочек атома каких-либо изменений в точке Ζ = Zc в этом случае не замечают.
A quick translation:
4.4. Until now, we have considered bare cores. But if 1S level is occupied by electrons, no visible effects appear when passing through Ζ = Zc. An electron cloud carrying a charge —2e is formed either by two electrons at the lower (discrete) level for Ζ < Zc or by perturbation of the continuum functions near the energy ε = ε0 < —1 for Z > Zc. If we integrate the charge density over the entire continuous spectrum, then for Ζ > Zc we get (after renormalization) exactly an extra —2е charge. Although formally the K-shell for Ζ > Zc is disappeared (from single-particle solutions of the Dirac equation), its role is assumed by the continuous spectrum. Therefore, for example, the electrons of the outer atomic shells do not notice any changes at the point Ζ = Zc in this case.
Droog Andrey (talk) 20:37, 25 February 2018 (UTC)
@Droog Andrey: Fascinating, thank you! I see the standard term for atoms with Z > Zcr is "supercritical atom" (e.g. here). I'll soon do the necessary rewrites. Double sharp (talk) 04:43, 26 February 2018 (UTC)
I have added a brief mention of supercritical atoms and mention that Z ≈ 173 looks like it is not going to be a limit either. I suppose that the real end is going to be dictated by nuclear properties; has anyone predicted where that would be? Double sharp (talk) 15:31, 11 March 2018 (UTC)

Why would period 8 end at Usb instead of Uho?[edit]

The 5g won't have 22 electrons given that square numbers are 1, 4, 9, 16, 25,..., not 1, 4, 9, 16, 27,... So Uho is noble gas, Uhe is alkali metal, Usn is alkaline earth and Usu to Ust are the last subcritical elements, being superactinides. 80.98.179.160 (talk) 11:41, 20 March 2018 (UTC)

It's all covered in the article. 5g still has 18 electrons, but it's not the only one being filled. Speaking of blocks here is a little silly, but after 8s fills at elements 119 and 120 we have lots of shells with similar energy levels that overlap. The ground-state electron configurations of the neutral atoms (given in the article) are a complete mess with lots of overlap, but if you consider doubly charged cations you can simplify what happens. A reasonable way to account things would be to say that two electrons of 8p (elements 121 and 122) and two electrons of 6f (elements 123 and 124) fill up before 5g proper (elements 125 to 142), so the run of eighteen is delayed (so these elements should be predominantly hexavalent or more, losing the outer 6f28s28p2 electrons, although promotion of one or two inner 5g electrons like the lanthanides do with their 4f electrons may be possible). Then the rest of 6f fills (elements 143 to 154) creating a series similar to the actinides (where at first the 6f electrons are all mostly chemically active, but at the end everything starts to fall into the core), before 7d (elements 155 to 164) and 9s (elements 165 and 166). (Because of the very long inner transition series the effective nuclear charge has risen so much that 8s is completely drowned into the core; the relativistic stabilisation of the s-shells that penetrate the nucleus also means that 7d is closer in energy to 9s than 8s.) Then we get two electrons of 9p (elements 167 and 168 – the p-subshells are split) and then finally the rest of 8p (elements 169 to 172). (It should be emphasised that though this narrative of when each electron shell is filled is based on the electron configurations given by Fricke, and is partly based on the comments he gives, there are likely to be no real boundaries here between blocks in the sense that the chemistry of the superactinides is likely to be a narrative of continuous change instead and the blocks are only formal.) So in addition to the Madelung 8s-5g-6f-7d-8p sequence we get four extra electrons from the 9s and part of the 9p subshells along the way, extending the row from 168 to 172. Double sharp (talk) 13:53, 20 March 2018 (UTC)
P.S. This has some similarities to the "intruder levels" of the nuclear shell model, which should have been part of the next shell but are lowered by spin–orbit coupling effects. In fact it is also why the next proton magic numbers past 82 are predicted to be 114 and 164, rather than 126 and 184 as would be expected (continuing the pattern and following known and expected neutron magic numbers). Double sharp (talk) 06:30, 26 March 2018 (UTC)

Access date[edit]

@Headbomb: Just wondering, how do you justify the |access_date= in your recent edits? YBG (talk) 04:53, 2 August 2018 (UTC)

P.S., by rights, WP:BRD says you should not have restored your bold edit that I reverted without first discussing it here. YBG (talk) 04:53, 2 August 2018 (UTC)
I have no idea what you're talking about by "justify the |access_date=". There were no urls, so I removed the access-date, this is standard stuff. You seem to be under the impression that I somehow added accessdates. Headbomb {t · c · p · b} 05:17, 2 August 2018 (UTC)
Let me double-check. YBG (talk) 07:38, 2 August 2018 (UTC)
I was absolutely wrong, you removed the |access_date= along with the url. I have no idea how my carelessness occurred, but carelessness it ws, and you have my heart-felt apologies. Thank you for WP:AGF! Happy editing! YBG (talk) 07:44, 2 August 2018 (UTC)