Shell structure of atoms

The average local electrostatic potential function, V(r)/rho(r), is calculated for 87 atoms and the corresponding mono-positive and mononegative ions in the ground state, using the nonrelativistic average-over-configuration numerical Hartree-Fock density. It is found in general that the shell boundaries are expressed as the successively increasing maxima in V(r)/rho(r) and the outermost maximum presents good approximate estimates of the core-valence separation in atoms. The reason for such behaviour is explained analytically. The proposed function is identified as the inverse of charge capacity per unit volume which attains a maximum at the shell boundary.