Comments on the paper by A. D. Walsh

Abstract

Theoretical justification for a relationship between ionization potential ( I ) and electronegativity ( x ) rests in the equation derived by Mulliken (1934, 1949), viz.: X = I + E / 2 where E is the electron affinity. Elements situate on the left-hand side of the Periodic Table have small E values, so that in these cases a direct relationship between x and I might be anticipated. On the right-hand side of the Periodic Table, the electron affinities may be appreciable, and for example in the halogens, are of the order 3 to 4 eV. The neglect of the term in E in these instances represents a serious departure from Mulliken’s equation. It is furthermore important to stress that the values of I which apply in the Mulliken equation are ‘valence-state’ ionization potentials, and are not in general to be identified with the first ionization potentials of the elements, which Walsh has employed. The relationships observed by Walsh might, in consequence, be misleading in cases where the ionization potential of the ground-state of an atom is far removed (in energy) from the ionization potential of the atom in its appropriate valence-state (e.g. Zn, Cd, Hg).