Roentgenium is a chemical element with symbol Rg and atomic number 111. It is an extremely radioactive synthetic element (an element that can be created in a laboratory but is not found in nature); the most stable known isotope, roentgenium-282, has a half-life of 2.1 minutes. Roentgenium was first created in 1994 by the GSI Helmholtz Centre for Heavy Ion Research near Darmstadt, Germany.
111
Atomic Number
282
Atomic Mass (u)
28.7
Density (solid: g/cm³, gas: g/liter)
151
Electron Affinity
7
Number of Shells
2, 8, 18, 32, 32, 17, 2
Electron Shell Occupations