 As supercritical atoms are expected to pose no difficulties with their electronic structure, the end of the periodic table may be determined by nuclear instability rather than electron shell instabilities.The stability of nuclei decreases greatly with the increase in atomic number after curium, element 96, so that all isotopes with an atomic number above 101 decay radioactively with a half-life under a day, with an exception of dubnium-268.No elements with atomic numbers above 82 (after lead) have stable isotopes.