To take the nuclear motion contribution into account, we traditionally evaluate the normal mass epsilon(nm) and specific mass (mass polarization) epsilon(sm) corrections separately and add them to the total electronic energy of atoms and ions calculated in the fixed-nucleus approximation. We point out that the sum of these mass corrections epsilon(mass) = epsilon(nm) + epsilon(sm) is immediately and rigorously obtained from the electron-pair moments in momentum space. The Hartree-Fock limit values of the mass correction sum epsilon(mass) are reported for the 102 neutral atoms He through Lr, singly charged 53 cations Li+ through Cs+, and 43 stable anions H-through I- in their experimental ground states. (C) 2002 Elsevier Science B.V. All rights reserved.