[en] A Gold ion with charge eQ has N = 197 Nucleons, Z = 79 Protons, and (Z-Q) electrons. (Here Q is an integer and e is the charge of a single proton.) The mass is m = au - Qm_e + E_b/c² (1) where a = 196.966552 is the relative atomic mass (1, 2) of the neutral Gold atom, u = 931.494013 MeV/c² is the unified atomic mass unit (3), and m_ec² = .510998902 MeV is the electron mass (3). E_b is the binding energy of the Q electrons removed from the neutral Gold atom. This amounts to 0.332 MeV for the helium-like gold ion (Q = 77) and 0.517 MeV for the fully stripped ion. For the Au³¹⁺ ion we have E_b = 13.5 keV. These numbers are given in Ref. (4). The deuteron mass (3) is 1875.612762(75) MeV/c².