Roentgenium (Rg)

Isotopes of Roentgenium 

Isotope Atomic Mass Half-life Mode of Decay
Rg-272 272.1535 0.0015 seconds α to Mt-268
Rg-279 279 0.17 seconds α to Mt-275
Rg-280 280 3.60 seconds α to Mt-276


Roentgenium was first synthesized in 1994 at the Gesellschaft für Schwerionenforschung (Institute for Heavy Ion Research — GSI) in Darmstadt, Germany, by an international team led by Sigurd Hofmann. Chemically, roentgenium should be in the same group as the elements copper, silver, and gold. Its name honors German physicist Wilhelm Conrad Röntgen (also spelled Roentgen), the discoverer of x-rays.

Roentgenium is calculated to have similar properties to its lighter homologues — copper, silver and gold — although it may show some differences as well. It is predicted to be a noble metal, and it is expected to be a solid under normal conditions and to crystallize in the body-centered cubic structure. All of its isotopes are extremely unstable and radioactive; in general, the heavier isotopes are more stable than the lighter.

Properties of Roentgenium

Name Roentgenium
Symbol Rg
Atomic number 111
Atomic weight [280]
Standard state Presumably a solid at 298 °K
CAS Registry ID 54386-24-2
Group in periodic table 11
Group name None
Period in periodic table 7
Block in periodic table d-block
Color Unknown, but probably metallic and silvery white or grey in appearance
Melting point No data available
Boiling point No data available
Density of solid 28.7 g/cm3 (predicted)
Electron configuration [Rn]5f146d97s2

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