Electronegativity: the distance factor

Abstract

Since its introduction by Linus Pauling in the 1930s, electronegativity has been defined as the power of a neutral atom in a molecule to attract electrons. However, while other powers of attraction involve a dependence on distance, no such distance dependence is routinely associated with electronegativity. A distance-corrected electronegativity function has been developed with X c= X(A)exp[−( R(AB)− R(A))] where X(A) is the electronegativity of atom A, R(AB) is the bond distance of interest, and R(A) is the appropriate quantum mechanically calculated atomic radius. Linear correlations have been found between several properties of the hydrogen and alkali metal halides and the distance-corrected electronegativity difference. These properties include ionicity, dissociation energy, heat of formation, stretching frequency, force constant, and lattice energy. The expansion of electronegativity from a constant to a distance-dependent function with two equivalent forms provides an insight to the importance of the bond distance on the property–electronegativity correlations.