The neutron and proton separation energies and mean square charge radii are evaluated within the Woods--Saxon plus BCS model for even--even nuclei with 40 \leq A \leq 256. The various parametrizations of the Woods--Saxon potential are examined. The improved values of the constants of the central part of Woods--Saxon potential are determined from a least-square adjustment to the existing experimental data.

PACS numbers: 25.85.Ca, 21.60.Ev, 21.10.Tg