At Last, A Definitive Periodic Table?

  • DOI: 10.1002/chemv.201000107
  • Author: David Bradley
  • Published Date: 20 July 2011
  • Source / Publisher: ChemistryViews.org
  • 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 ChemistryViews.org 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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5 Comments

Philip Stewart wrote:

Gaps

All gaps and breaks in the uninterrupted sequence of elements are the artificial result of chopping it into sections. Only a spiral or helical representation avoids this.

Sun Jul 24 07:17:30 UTC 2011

Valery Tsimmerman wrote:

Correction

Helium has first shell completely filled, Ne has first two shells completely filled, Zn has first three shells completely filled and Yb has first four shells completely filled, but only He and Ne have all shells completely filled because both are light elements. No other noble gases have completely filled shells. If we accept that completely filled shells make He and Ne structurally similar, we can not say the same about Ne and Ar, since Ar does not have all shells filled.

Sun Jul 24 06:14:14 UTC 2011

Valery Tsimmerman wrote:

H next to He

I believe that H and He belong next to each other, in that I agree with Eric. I also believe that H has to be above (or next) to Li, in that I agree with traditional periodic table. Finally, I believe that He belongs next to Be. In that I agree with Janet.___ Helium structurally resembles Be more than Ne. Eric's argument that He is structurally close to Ne because both have completely filled shells is not valid, because having shells completely filled does not make elements structurally similar. For example, Zn and Yb also have shells completely filled, but it does make them similar neither to Ne, nor to He. This leaves only one Eric's table that is more or less agrees with my views: Janet-Stowe-Scerri. It is certainly improvement to Stowe, because it is based on n+l. However it has few serious draw backs: 1) absence of tie lines makes it hard to follow elements from layer to layer, finding the elements without already knowing where to look for them is also hard; 2) electron shells are left unidentifiable; 3) color is used for marking subshells, therefore it can not be used to identify families/properties of the elements.

Sun Jul 24 04:58:01 UTC 2011

Eric Scerri wrote:

Response to Philip

Nice to be unique in at least one respect! So what about the further point I raised? How relevant is it to close the gap between H and He in the opinion of the punters on this forum? Is it just cosmetic? Does it represent a real advance over the medium-long form table? eric

Sun Jul 24 01:14:11 UTC 2011

Philip Stewart wrote:

Janet's H over F, He over Ne version

Eric: the table in your 2008 article was Janet's Version I in his article of May 1928, replaced by his definitive Version III in his article of November of that year. It is also the table published by L M Simmons in his article in J Chem Ed in December 1947. He knew of Janet's work only from the disastrous article in Chemical News, and he rather ungallantly said: "[His] insistence on coiling the chart, together with the paucity of explanation, cause Janet's table to be regarded as only touching the fringe of the present arrangement." He too abandoned his copy of Janet Version I in in his article in J Chem Ed in December 1948 and opted for the full Janet table. So you are the only person who has not so far moved from Version I to Version III.

Sat Jul 23 20:28:42 UTC 2011

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