The periodic table has been stamped into the minds of countless generations of schoolchildren. Immediately recognised and universally adopted, it has long since achieved iconic status.
So why change it? According to Mohd Abubakr from Microsoft Research in Hyderabad, the table can be improved by arranging it in circular form. He says this gives a sense of the relative size of atoms–the closer to the centre, the smaller they are–something that is missing from the current form of the table. It preserves the periods and groups that make Mendeleev’s table so useful. And by placing hydrogen and helium near the centre, Abubakr says this solves the problem of whether to put hydrogen with the halogens or alkali metals and of whether to put helium in the 2nd group or with the inert gases.
That’s worthy but flawed. Unfortunately, Abubakr’s arrangement means that the table can only be read by rotating it. That’s tricky with a textbook and impossible with most computer screens.
The great utility of Mendeleev’s arrangements was its predictive power: the gaps in his table allowed him to predict the properties of undiscovered elements. It’s worth preserving in its current form for that reason alone.
However, there’s another relatively new way of arranging the elements developed by Maurice Kibler at Institut de Physique Nucleaire de Lyon in France that may have new predictive power.
Kibler says the symmetries of the periodic table can be captured by a group theory, specifically the composition of the special orthogonal group in 4 + 2 dimensions with the special unitary group of degree 2 (ie SO (4,2) x SU(2)).
That gives a layout as follows:
Kibler’s approach is akin to the way particle physicists classify particles by their symmetry properties such as flavor and color. That has been hugely useful in predicting the existence of new particles. Can the power of this group theoretical approach have the same impact on chemistry?
The problem for Kibler (and anybody else attempting to redraw the table of elements) is that we seem to have already found all the stable elements and predicted the existence of other superheavy ones. The question is whether Kibler’s approach has any predictive power beyond that. Maybe but the jury (and Kibler himself) is still out on this one.
arxiv.org/abs/0910.0273: An Alternate Graphical Representation of Periodic table of Chemical Elements
arxiv.org/abs/quant-ph/0408104: On a Group-Theoretical Approach to the Periodic Table of Chemical Elements