copper group element atom roentgenium atom LJROPTGWFUZRDB-UHFFFAOYSA-N chebi_ontology Rg Roentgenium CHEBI:33368 A copper group element atom with atomic number 111. The the ninth member of the 6d series of transition metals, it is an extremely radioactive, synthetic element. Average mass is around 281. 0.00000 WebElements:Rg Wikipedia:Roentgenium 0 111Rg 0.000 unununium [Rg] Rg InChI=1S/Rg roentgenium Uuu roentgenio roentgenium