Wöhler’s Urea Synthesis

Katz, G. The Periodic Table: An Eight Period Table For The 21st Centrury. Chem. Educator 2001, 6 (6), 324–332; DOI 10.1007/ s00897010515a.

Eric Scerri

University of California Los Angles, Department of Chemistry & Biochemistry, 607 Charles E. Young Drive East, Los Angeles, CA 90095-1569, scerri@chem.ucla.edu

I wish to respond to some comments made about my published work on the periodic system in a recent article by Gary Katz which appeared in The Chemical Educator. I am afraid the author has misquoted me as well as taking my published remarks out of context with the result that he makes me appear anti-quantum mechanical. Nothing could be further from the truth. Katz cites me as saying that "quantum mechanics cannot explain the periodic table".

This passage has been fabricated by Katz from fragments of what I wrote. As a matter of fact what I wrote in my article in Scientific American was the following.

"Despite the efforts of chemists and physicists quantum mechanics cannot explain the periodic table any further. For example it cannot explain explain from first principles the order in which electrons fill the various electronic shells. The electronic configurations of atoms, on which our modern understanding of the periodic table is based, cannot be derived using quantum mechanics... As a result quantum mechanics can only reproduce Mendeleev's original discovery by the use of mathematical approximations- it cannot predict the periodic system."

This is quite different from saying simply that quantum mechanics cannot explain the periodic table.

I have never made such a claim but only have tried to make the more subtle point that the order of filling of orbitals is not derived in a strictly ab initio fashion form QM (1). I do this because I think it would be a worthwhile goal to strive for and because until this has been achieved I think that the reductive claims of quantum mechanics in chemistry should be qualified.

Nevertheless, I believe that Katz's article is an important one and am pleased to see it published. He has made what I think is the best case yet for the reform of the periodic table into what I prefer to call the fdps format. This table has the added advantage of displaying the doubling of all period lengths whereas the conventional form shows an anomaly with the first period length not being repeated. The need to display the symmetry of the periodic system is a point I also made in the Scientific American article which Katz cited (2).

The most controversial aspect of Katz's suggestion, which has been made before as he readily concedes, is the placement of He among the alkaline earths. I note with some interest that Katz has an original explanation to justify doing this or at least for disconnecting H and He from the rest of the table.

I would be interested in hearing from other people as to their opinions about such a proposed table which I regard to be rather desirable.

References

1. Scerri, E. R. How Good is the Quantum Mechanical Explanation of the Periodic Table? J. Chem. Educ. 1998, 75, 1384–1385.

2. Scerri, E.R. The Evolution of the Periodic System Sci. Am. 1998, 279 (Sep), 78–83.