243Am+48Ca reactions. The multiplicity of excited states populated by the alpha decay of odd nuclei may however preclude clear cross-bombardment cases, as was seen in the controversial link between 293Ts and 289Mc. Heavier isotopes are expected to be more stable; 320Ubu is predicted to be the most stable unbiunium isotope, but there is no way to synthesize it with current technology as no combination of usable target and projectile could provide enough neutrons. The teams at RIKEN and at JINR have listed the synthesis of element 121 among their future plans. These two laboratories are best suited to these experiments as they are the only ones in the world where long beam times are accessible for reactions with such low predicted cross-sections. Naming Using Mendeleev's nomenclature for unnamed and undiscovered elements, unbiunium should be known as eka-actinium. Using the 1979 IUPAC recommendations, the element should be temporarily called unbiunium (symbol Ubu) until it is discovered, the discovery is confirmed, and a permanent name chosen. Although widely used in the chemical community on all levels, from chemistry classrooms to advanced textbooks, the recommendations are mostly ignored among scientists who work theoretically or experimentally on superheavy elements, who call it "element 121", with the symbol E121, (121), or 121. Nuclear stability and isotopes The stability of nuclei decreases greatly with the increase in atomic number after curium, element 96, whose half-life is four orders of magnitude longer than that of any currently known higher-numbered element. All isotopes with an atomic number above 101 undergo radioactive decay with half-lives of less than 30 hours. No elements with atomic numbers above 82 (after lead) have stable isotopes. Nevertheless, for reasons not yet well understood, there is a slight increase of nuclear stability around atomic numbers 110–114, which leads to the appearance of what is known in nuclear physics as the "island of stability". This concept, proposed by University of California professor Glenn Seaborg and stemming from the stabilizing effects of the closed nuclear shells around Z = 114 (or possibly 120, 122, 124, or 126) and N = 184 (and possibly also N = 228), explains why superheavy elements last longer than predicted. In fact, the very existence of elements heavier than rutherfordium can be attested to shell effects and the island of stability, as spontaneous fission would rapidly cause such nuclei to disintegrate in a model neglecting such factors. A 2016 calculation of