Hassium (Hs). Diagram of the nuclear composition and electron configuration of an atom of hassium-269 (atomic number: 108), the most stable isotope of this radioactive element. The nucleus consists of 108 protons (red) and 161 neutrons (yellow). 108 electrons (white) bind to the nucleus, successively occupying available electron shells (rings). Hassium, named for where it was first synthesised in 1984, is a transactinide and transition metal in group 8, period 7, and the d-block of the periodic table. Hassium-269 has a half-life of 9.7 seconds, its nucleus emitting an alpha particle to form seaborgium-265.