Roentgenium

Roentgenium (IPA: /ˌr(ə/o)ʊntˈgɛniəm/, formerly Unununium) is a chemical element in the periodic table that has the symbol Rg and atomic number 111, making it one of the super-heavy atoms. It is a synthetic element whose longest-lived isotope has a mass of 280 and a half-life of 3.6 seconds. Due to its presence in Group 11, it is a transition metal.