At Last, A Definitive Periodic Table?

  • DOI: 10.1002/chemv.201000107
  • Author: David Bradley
  • Published Date: 20 July 2011
  • Source / Publisher:
  • Copyright: WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
thumbnail image: At Last, A Definitive Periodic Table?

Discussion Spawned Development in the Field

A recent Research Highlight on on the nature of the Periodic Table of the Elements attracted a lot of readers and has stimulated an ongoing debate among those arguing as to whether or not there is a definitive format for this iconic tool. Intriguingly, however, the article and ensuing discussion has also spawned a development in this field courtesy of UCLA chemistry professor Eric Scerri.

"One of the most positive outcomes of the very popular 'Periodic Debate' discussion has been that the relative virtues of the so-called 'Stowe' and the 'left-step' periodic table, in various formats, have been vigorously discussed," Scerri says. "In the course of this debate I have come up with a compromise table which includes the best features of both types of systems."

Stowe Table

The Stowe table is named for Tim Stowe who published his system on a website several years ago but has, apparently, published nothing since. Chemists have attempted to track him down, but he seems to have vanished from the community without a trace, leaving behind an interesting periodic legacy. "Many people interested in the periodic table have tried to track him down," says Scerri, "but nobody has yet succeeded."

Stowe’s system is four dimensional in the following sense: the x and y axes depict values of the m and s quantum numbers. In the case of the s or spin quantum number values are either positive or negative, while the values of the m quantum number can range from -l, through 0 up to +l in integer steps. The z-axis is taken as the n or main quantum number representing the main shell. The fourth dimension, which obviously cannot be depicted spatially, is shown by the use of different colors each of which denotes a different value of the l quantum number. In this way, the Stowe table seeks to depict the four quantum numbers of the electron that differentiates each atom from the previous one in the sequence of increasing atomic numbers.

However, the Stowe representation has several drawbacks, which is where Scerri's new approach comes to the fore. The left-step table has received a great deal of attention in recent years. It was originally designed by the French engineer and polymath Charles Janet in the 1920s. However, with the advent of quantum mechanics and the quantum mechanical account of the periodic system it was realized that his system displays the elements in order of increasing n + l values of the differentiating electron. Many authors have claimed that this is a more natural system since electron filling accords with this criterion rather than increasing values of n.

New Modifications by Scerri

Scerri has now modified the left-step table by combining it with Stowe’s idea of using the quantum numbers explicitly to represent the elements in the periodic system. "The notion that n + l is more fundamental than n alone is key," says Scerri. "The format I have now constructed depicts the arrangement of the elements in this fashion for elements 1 to 65 inclusive and can be easily extended up to 118 the currently heaviest atom and indeed beyond to elements that will in all probability be
synthesized soon." In what he now calls the Stowe-Janet-Scerri periodic system each level represents a particular value of n + l which take the form of horizontal periods in the case of the original Janet table.

Following Scerri's introduction of this new layout in the comments of the ChemistryViews item, commenter Valery Tsimmerman, pointed out that Scerri's efforts in re-working the Stowe table is bringing us closer to the realization of the numerical and geometrical regularities of the Periodic System. Tsimmerman also claims to have devised the perfect Periodic Table based on the concept of tetrahedral sphere packing.

Tsimmerman's Concept of Tetrahedral Sphere Packing

Tsimmerman points out that chemists such as Henry Bent mentioned that every other alkaline earth atomic number equals to four times the pyramidal number, while Wolfgang Pauli noticed that length of periods are double square numbers: 2x(1, 4, 9, 16). This latter point is, Tsimmerman says, not surprising because square numbers are the sums of odd numbers 1, 1+3, 1+3+5, 1+3+5+7 ... We know the meaning of odd numbers in the periodic system. They are the lengths of s, p, d and f blocks. Adding the number of elements in block rows results in the lengths of the periods. Adding square numbers results in pyramidal numbers: 1, 1+4=5, 1+4+9=14, 1+4+9+16=30. Multiply them by four and you will get every other tetrahedral number 4, 20, 56, 120 ... Those are the atomic numbers of Be, Ca, Ba and Ubn. "Great scientists like Pauli, Niels Bohr and others were marveling at numerical relationships found in periodic system," says Tsimmerman. He suggests that Scerri's latest periodic table is not quite the final version and suggests that any further reworking of Stowe's table will take us closer to a definitive 3D table.

"I hope that this system will not be just another periodic table to add to the depository of tables that people dream up every so often but may represent a definitive step forward in the quest for improved periodic tables," Scerri told us.

  • Periodic Debate, David Bradley
    Mendeleev's Periodic Table is, for many, the symbol of chemistry but is the current layout the best one?
    including discussion mentioned in article

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Philip Stewart wrote:


There was a suggestion that element 114 behaved like a noble gas (Janet thought it might!). And how noble is Rn? And what about monatomic Hg gas? The impression is that [ig]nobility is seriously sporadic in these very heavy regions.

Sat Jul 30 21:23:35 UTC 2011

Jess Tauber wrote:

re: response to Bernard and new proposal to others

Well, if we're going to talk about breaking symmetry and the He/noble gas issue, what about the prediction that element 118, which by right of tabular position *should* be noble, likely will not be. Here we would have spin-orbit properties outweighing others so it also will not fit in with the usual noble suspects. On the other hand, if 120 DOES turn out to be noble, again by some predictions, then it will symmetrically mirror He, if 120 is in some sense the end of the system. I've mentioned this more than once elsewhere, but never have gotten any satisfactory response.

Sat Jul 30 16:14:13 UTC 2011

Eric Scerri wrote:

response to Bernard and new proposal to others

If your system amounts to just a modification of the medium-long form in order to move He one should perhaps make that point more clearly instead of implying a major change, as I think you do.____________ In any case wanting to move He to group 2 places one in opposition to most chemists. Part of this debate is about whether reduction to physics can be pushed so far as to ignore chemical evidence altogether. _____ Helium sure looks like it is similar to the other noble gases in terms of chemical behavior. What right does the physicist have to tell the chemist where to place elements? _______________Is it not possible that the perfect symmetry of physics is somewhat broken at the more 'superficial' level of chemical behavior? Should the physicist not rather be working on some form of symmetry breaking mechanism to justify why He behaves like the noble gases in a chemical sense while really being an alkaline earth at a fundamental level? After all physicists who argue for a unification of the four forces of nature don't just leave it at that. They look for the actual mechanism of symmetry breaking to justify the parting of the ways between the four forces at more accessible energies or at the level that we typically live at. I would be interested in comments from any or all protagonists here including Philip and Valery.

Sat Jul 30 15:53:41 UTC 2011

Bernard Schaeffer wrote:

Medium-long form

The Figure 1: Medium-long form of the Periodic Table is 99% (approximately of course…) quantum mechanically correct. Lu and Lr are correctly below Sc and Y. Only helium is not at the right place. Indeed a vacant box waits for it above Be. Otherwise there is no difference with my table ( or issues/11-2/scerri_fig2.gif (I tried to paste it here without success) Bernard

Sat Jul 30 09:23:01 UTC 2011

Eric Scerri wrote:

Bernard Schaeffer's suggestion

I think there is a good deal of merit in Bernard's suggestion. A comittment to He in the alkaline earths and placing Lu and Lr in group 3 does not necessarily commit one to a left-step table. _____________ We can stay with the conventional medium-long form while making these three changes. The only 'loss' is that periods are not arranged according to increasing values of n + l. ________________________So Bernard, if you claim to base yourself on QM why not also accept the left-step format? What I am trying to do here is to be clear about the difference between Bernard's suggestions and some of the tables we have been discussing on this forum such as Janet, Stowe etc. We are all aware of the need to reconcile the periodic table with QM. The question is just how to do it. I also think that talk of 97% agreement is a little misleading given that we now know of 118 rather than 100 elements.________eric

Fri Jul 29 17:32:28 UTC 2011

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