Ion-Neutral Bonding

Abstract

Electrostatic calculations of bond energy are made for a variety of ion‐neutral systems, and where possible the calculations are compared with experimental results. An independent semiempirical determination of ion repulsive potentials allows accurate calculation of bond energies for H₂O molecules clustered to all alkali (+) and halide (−) ions; the cases of one and two H₂O molecules are computed here. Contrary to previous estimates on these systems, the ion‐quadrupole energy is small and there is very little, if any, covalent bonding in ${\mathrm{F}}^{-}·{\mathrm{H}}_2\mathrm{O}$ . Bond energies and entropies of association are computed for alkali (+) and F⁻ ions with O₂, N₂, and CO₂; the results yield predictions of equilibrium constants. Relative bond strengths of these neutrals with any one ion are determined by the ion‐quadrupole energies. The bond energies of Mg²⁺, Ca²⁺, and Ba²⁺ with O₂, N₂, CO, CO₂, N₂O, and H₂O are approximated. The molecular hyperpolarizability is very important in the bonding of doubly ionized atoms and is capable of explaining several anomalies in experimental termolecular association rate constants. The bonding of molecular ions is discussed and the ${\mathrm{O}}_2^{+}$ repulsive potential is derived and used to compute the ${\mathrm{O}}_2^{+}·{\mathrm{H}}_2\mathrm{O}$ bond energy.