Shell corrections to a liquid-drop description of nuclear masses and radii

It is shown that a consistent treatment of nuclear bulk and surface effects leads to an improved version of the liquid-drop mass formula with modified symmetry and Coulomb terms. If in addition shell effects are modelled through the counting of the number of valence nucleons, a very simple mass formula is obtained with an rms deviation from the 2003 database of atomic masses of about 800 keV. As an application, the volume and surface symmetry energy for A -> infinity are determined. A similar description of nuclear radii is suggested with specific reference to the neutron skin.