Observations on the Significance of the Electrostatic Potentials at the Nuclei of Atoms and Molecules

The first portion of this paper reviews the development of a series of relationships, both exact and approximate, between the energies of atomic and molecular systems and the total electrostatic potentials at the nuclei in these systems. Mathematical formulations are presented for such properties as the energy of the valence electronic charge of an atom, and the energies associated with the individual atoms in a molecule. An equation is obtained that relates the energy of a molecule to the changes in the electrostatic potentials at the nuclei of the free atoms when they combine to form the molecule. The second portion of the paper discusses some properties of the potentials at nuclei, including their remarkable insensitivity to the environments of the nuclei. It is pointed out that the potentials at nuclei serve as links between theory and various experimental techniques, including electron spectroscopy, nuclear magnetic resonance, and Mossbauer spectroscopy. A general theme of this paper is that the electrostatic potentials at nuclei are a fundamental and unifying property of atomic and molecular systems, which can help to clarify and generalize some very basic concepts.