Kimball atoms Li to Ne, revisited: in Preparation


This is an artists view of the atoms Li to Ne with their "electronic rabbit ears", ready to accept ligands: light blue: single electron cloud; deep blue: doubly occupied; red: 1s2 core cloud


from Kimball-Model in chemistry didactics at ETH, Zürich (by Dr. Urs Wuthier). If this link has been killed by the inquisition, try here or another set. (Lewis atomic dot symbols of electrons and electron pairs added to point out analogy, by ES).

With and without rabbit ears

I'm sure that G.E. Kimball would not have liked these qualitative pictures and know that some theoretical chemists give a deadly verdict like "trash" to it. However, although you will not find this exact picture anywhere in the Columbia theses of Kimball's doctorands, they have been used, e.g. for deriving the arithmetics to compute the hydrides LiH to HF (L.M. Kleiss, loc. cit.) and for building CH, ..., CH4. Furthermore, G.E. Kimball and J.G.Trulio, JCP 28,493(1958) have presented the "Quantum Mechanics of H3" and given the proof that all molecular structures can be described accurately with a large → infinite number of H(1s)-functions. That is essentially, what the above picture of (a still small number!) of non-overlapping spherical functions i of variable R(i) shows, R(i) depending on interaction with the Coulomb fields of the other particles nearby and their quantum chemical zero point kinetic energy. These "rabbit-ear" atoms are just a bit more elaborate than G.N.Lewis' single and double dots with which he decorated atom symbols to express their "bonding number". This has been accepted by chemists since the thirties of last century. Lewis tried
in vain to attach quantitative significance in the sense of energy values to this electron pair bonding scheme (in 1916 QM was still 10 years away). G.E. Kimball, however, has succeeded to attach a quantitative aspect to a blown-up spherical Lewis-dot, avoiding the big machinery of Quantum Chemistry, many chemists do not properly understand, anyway! Lewis' dashes and dots, even tapered to render them 3D aware, are a big part of the symbolic language of organic chemists. It is loaded with a wealth of empirical data not directly visible with the formulae. An analogy would be the score of a symphony which conveys pitch and duration of notes but presupposes, that every instrumentalist has learned over many years how to interpret the composers intentions behind the abstract notation. Most theoretical chemists have never learned nor understood the practical chemists' language. Hence, their verdict in regard to simple models is inadequate, and may be ignored. Organic chemists get results with this symbolic art in minutes without using a computer and in cases where todays' quantum chemists dare not even try.

Rabbit ears tested

The following link shows results for the quantitative "rabbit ear" atoms Li to Ne and up to K, depicting an "Aufbau" principle with H(1s) only. If you look at other properties than chemical reactivity, e.g. ionization potentials, the shell filling of the figure above does not give correct results. Among other data this is shown and explained in Kimballs_Atoms.

Do spherical atoms better ?

"Rabbit ear" atoms "pseudopotentially" sphericalized from Li to Cs: As already shown in Slater Kimballs atoms do not require rabbit ears. With an almost identical "Ansatz" the wavemechanical atom model can be simulated as spherically symmetrical, responding to the shell fillings as observed by spectroscopy and mass spectrometric ionization potentials and electron affinities. This and molecular interactions up to Xenon-Fluorides is documented with quantitative data in Spherical Atoms.