Charge capacities and shell structures of atoms

Abstract

This paper focuses upon two important features of atoms: their charge capacities and their shell structures. The charge capacity к is a measure of an atom's ability to accommodate a gain or loss of electronic charge in the process of forming a molecule. Estimated values of к are presented for the atoms Li-Xe. The overall trend is that as the inherent (neutral atom) electronegativity increases, к decreases. The shell structure of an atom can be discerned by plotting its local ionization energy Ī(r) against radial distance from the nucleus; it decreases in a roughly stepwise manner and the inflection points correspond to meaningful boundaries between the electron shells. An effective “outer radius” r_s for an atom can be defined in terms of the sphere that encompasses all but 0.2 of its electrons. For nearly three-fourths of the atoms, the outer shell is found to be 97% or more of the total volume. The computed populations, radii and volumes of all of the shells are presented for the atoms Li-Xe, as well as the magnitudes of Ī(r) at all shell boundaries. Good correlations exist between atomic polarizability, Ī(r_s), к and outer shell electron density. It is suggested that Ī(r) can be used as a measure of local polarizability, α(r), in atoms and molecules.