Valence-state energies of excited configurations involving 4s, 4p, and 3d orbitals in later second-row elements

Abstract

Valence-state energies of excited configurations involving 3d, 4s, and 4p, orbitals in later second-row elements (Si, P, S, and Cl) and their ions are computed from spectral term energies. Slater's treatment for complex atoms is found to be accurate in applications to these excited configurations. From valence-state energies, ionisation potentials and electron-affinities of outer-shell orbitals are estimated. The results indicate that for bivalent sulphur and univalent chlorine the weight of configurations involving high-energy orbitals is likely to be small. For later second-row atoms with high covalencies the weight is expected to be largely dependent on the degree of perturbation of the ligands and upon the contribution to bonding energies by the excited orbitals. In particular the 4s orbital is always a few eV more stable than 4p and 3d orbitals: thus the contribution of the former to the valence state is expected to be at least comparable or possibly larger than that of 3d orbitals.