Periodic Table of Elements




Roentgenium was discovered by research scientists at the Heavy Ion Research Laboratory in Darmstadt, Germany in 1994.

Name: Roentgenium
Symbol: Rg
Atomic number: 111
Atomic weight: 280.16
State: gas
Group, period, block: 11, 7, d
Color: unknown
Classification: unknown but probably a transition metal
Electron configuration: 5f14 6d9 7s2

Physical properties

Density: 28.7 g/cm-3
Melting point: no data
Boiling point: no data

Atomic properties

Oxidation states: 5, 3, 1, -1
Electronegativity: no data
Ionization energies: 1st: 1022.7 kJ·mol-1
Covalent radius: 121 pm
Van der Waals radius: no data
  • Rg
  • Electron Configuration


Roentgenium is an artificial element, and thus a standard atomic mass cannot be given. Like all artificial elements, it has no stable isotopes. The first synthesized isotope was 272Rg in 1994, which is also the only directly synthesized isotope. There are 7 known radioisotopes from 272Rg to 282Rg. The longest-lived isotope is 281Rg with a half-life of 26 seconds.