Distinguishing Bonds

The energy change per electron in a chemical or physical transformation, Delta E/n, may be expressed as Delta(chi) over bar + Delta(V-NN + omega)/n, where Delta(chi) over bar, is the average electron binding energy, a generalized electronegativity, Delta V-NN is the change in nuclear repulsions, and Delta omega is the change in multielectron interactions in the process considered. The last term can be obtained by the difference from experimental or theoretical estimates of the first terms. Previously obtained consequences of this energy partitioning are extended here to a different analysis of bonding in a great variety of diatomics, including more or less polar ones. Arguments are presented for associating the average change in electron binding energy with covalence, and the change in multielectron interactions with electron transfer, either to, out, or within a molecule. A new descriptor Q, essentially the scaled difference between the Delta(chi) over bar and Delta(V-NN + omega)/n terms, when plotted versus the bond energy, separates nicely a wide variety of bonding types, covalent, covalent but more correlated, polar and increasingly ionic, metallogenic, electrostatic, charge-shift bonds, and dispersion interactions. Also, Qitself shows a set of interesting relations with the correlation energy of a bond.