Flerovium is expected to crystallize in the face-centred cubic crystal structure like that of its lighter congener lead, although earlier calculations predicted a hexagonal close-packed crystal structure due to spin-orbit coupling effects. Those earlier calculations also predicted a density of 9.928 g/cm3, although this was noted to be probably slightly too low. The electron of the hydrogen-like flerovium ion (oxidized so that it only has one electron, Fl113+) is expected to move so fast that it has a mass 1.79 times that of a stationary electron, due to relativistic effects. For comparison, the figures for hydrogen-like lead and tin are expected to be 1.25 and 1.073 respectively. Flerovium would form weaker metal–metal bonds than lead and would be adsorbed less on surfaces.