Consideration of effective nuclear charge Z(eff) e in an electrostatic model, together with the pairwise combination of ionization potentials I (or of I with electron affinity), yields both a value of Z(eff) related to electronegativity and an averaged charge radius r related to polarizability. For anions the value of r is within a few percent of the experimental in-lattice radius from XRD. For cations, the positive charge external to the closed shells interacts with the latter as with a dielectric, again in accord with a model yielding realistic cation radii R : apart from Li salts, r + R values accord well with experimental lattice parameters, demonstrating further the applicability of electrostatic continuum models.