Configuration Energies of the Main Group Elements

Configuration energies (CEs), formerly called spectroscopic electronegativities, are an attempt to quantum mechanically define, and extend, the important chemical concept of electronegativity. In a previous paper (J. Am. Chem. Soc. 1989, 111, 9003) we reported high-resolution experimental values obtained from the National Institutes of Science and Technology spectroscopic energy level tables using the formula CE = (nεs + mεp)/(n + m). where n and m are the number of s and p electrons and εs and εp are their multiplet averaged one-electron energies, for the 34 s and p-block atoms H→Xe. This CE definition is a direct extension of N. Bohr's introduction of electron configurations to quantum mechanically rationalize the periodic table (hence its designation as configuration energy). Here we give experimental numbers for the remaining 8 sixth row representative atoms plus Zn, Cd, and Hg. In addition, we have carried out high accuracy numerical Dirac−Hartree−Fock solutions for all 45 atoms. Results from these calculations closely parallel the experimental values and enable us to estimate some of the atomic multiplet levels for which no experimental data exist. CE leads to numbers which are interpretable as an “electron attracting power” in the same manner as the traditional scales of Pauling and Allred & Rochow. They are also strongly correlated with atomic energy level spacings, therefore providing an additional interpretability compatible with energy level data and the molecular orbital diagrams that dominate much of contemporary chemistry. Likewise, CEs are able to rationalize the origin of the metalloid band (diagonal line separating metals from nonmetals) in the periodic table and the new determination of sixth row CEs permit designation of bismuth and polonium as metalloids, clarifying their previous uncertain classification between metal and metalloid.