Livermorium

Livermorium came out of the long Dubna-Livermore collaboration, in which the American laboratory supplied the exotic actinide targets — curium in this case — and the Russian laboratory supplied the calcium-48 beam and the separator. It was first observed in 2000 and named in 2012, honouring Lawrence Livermore National Laboratory and, through it, Ernest Lawrence, who also has element 103. Its longest-lived isotope survives about 60 milliseconds, far too short for any chemical experiment, so its predicted place under polonium as a post-transition metal remains entirely theoretical and the category is left unknown here. The electron configuration given is calculated, not observed.