Ununseptium (Uus). Diagram of the nuclear composition and electron configuration of an atom of ununseptium-294 (atomic number: 117), the most stable isotope of this radioactive element. The nucleus consists of 117 protons (red) and 177 neutrons (yellow). 117 electrons (white) bind to the nucleus, successively occupying available electron shells (rings). Ununseptium is a temporary name (2010 synthesis not yet official). It is a transactinide of unknown properties in group 17, period 7, and the p-block of the periodic table. The ununseptium-294 nucleus (half-life: 78 milliseconds) emits an alpha particle to form ununpentium-290.