We present a detailed analysis of the (ensemble-averaged) interaction between each of these ions and its short-range hydration sphere, in both bulk water and at the air/ water interface, using the quantum-chemical methods of symmetry-adapted perturbation theory (SAPT) . The SAPT family of methods is designed for accurate calculation of noncovalent interaction energies as well as a physically-motivated energy decomposition analysis of those energies . Of key interest will be whether the interfacial environment engenders any discernible changes in the ion-water interactions, relative to what is observed for the same ion in bulk water.