Localised molecular orbitals in self-consistent field wave functions. Part VIII. The role of the inner-shell electrons in molecule formation

Abstract

The role which the inner-shell electrons play in bond formation is analysed, using the known localised molecular orbitals of some molecules built from first-row atoms. The Is atomic orbitals do not enter the lone pairs appreciably but they do enter the valence atomic orbitals and increase their ionisation energies substantially. This has little effect on the covalency but it does affect the ionic terms significantly. The localisation routes used to get the Ione pairs and chemical bonds have been changed slightly so as to eliminate the unrealistic negative hybrids from the valence atomic orbitals. These two modifications of the earlier results lead to some changes in numerical values of the energy quantities and, in particular, the (–δe^µ) defined earlier (the increase in the ionisation energy of the bond on molecule formation) now show clearer connections with the experimental bond energies. The (–δe^µ) are now called the “one-electron binding energies” of the electron or of the molecular orbital.