the isotopes 308–310Ubb are predicted to have half-lives under 1 microsecond, too short for detection as a result of significantly lower binding energy for neutron numbers immediately above the N = 184 shell closure. Alternatively, a second island of stability with total half-lives of approximately 1 second may exist around Z ~ 124 and N ~ 198, though these nuclei will be difficult or impossible to reach using current experimental techniques. However, these predictions are strongly dependent on the chosen nuclear mass models, and it is unknown which isotopes of unbibium will be most stable. Regardless, these nuclei will be hard to synthesize as no combination of obtainable target and projectile can provide enough neutrons in the compound nucleus. Even for nuclei reachable in fusion reactions, spontaneous fission and possibly also cluster decay might have significant branches, posing another hurdle to identification of superheavy elements as they are normally identified by their successive alpha decays. Chemical Unbibium is predicted to be similar in chemistry to cerium and thorium, which likewise have four valence electrons above a noble gas core, although it may be more reactive. Additionally, unbibium is predicted to belong to a new block of valence g-electron atoms, although the 5g orbital is not expected to start filling until about element 125. The predicted ground-state electron configuration of unbibium is either [Og] 7d1 8s2 8p1 or 8s2 8p2, in contrast to the expected [Og] 5g2 8s2 in which the 5g orbital starts filling at element 121. (The ds2p and s2p2 configurations are expected to be only separated by about 0.02 eV.) In the superactinides, relativistic effects might cause a breakdown of the Aufbau principle and create overlapping of the 5g, 6f, 7d and 8p orbitals; experiments on the chemistry of copernicium and flerovium provide strong indications of the increasing role of relativistic effects. As such, the chemistry of elements following unbibium becomes more difficult to predict. Unbibium would most likely form a dioxide, UbbO2, and tetrahalides, such as UbbF4 and UbbCl4. The main oxidation state is predicted to be +4, similar to cerium and thorium. A first ionization energy of 5.651 eV and second ionization energy of 11.332 eV are predicted for unbibium; this and other calculated ionization energies are lower than the analogous values for thorium, suggesting that unbibium will be more reactive than thorium. Notes References Bibliography External links Chemistry-Blog: Independent analysis of Marinov's 122 claim Chart