Roentgenium is a synthetic radioactive chemical element with the symbol Rg and atomic number 111. It is placed as the heaviest member of the group 11 (IB) elements, although a sufficiently stable isotope has not yet been produced in a sufficient amount that would confirm this position as a heavier homologue of gold.
Roentgenium/unununium was first observed in 1994 and several isotopes have been synthesized since its discovery. The most stable kno...
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Roentgenium is a synthetic radioactive chemical element with the symbol Rg and atomic number 111. It is placed as the heaviest member of the group 11 (IB) elements, although a sufficiently stable isotope has not yet been produced in a sufficient amount that would confirm this position as a heavier homologue of gold.
Roentgenium/unununium was first observed in 1994 and several isotopes have been synthesized since its discovery. The most stable known isotope is Rg with a half-life of ~26 seconds, which decays by spontaneous fission, like many other N=170 isotones.
Roentgenium was officially discovered by an international team led by Sigurd Hofmann at the Gesellschaft für Schwerionenforschung (GSI) in Darmstadt, Germany, on December 8, 1994. Only three atoms of it were observed (all Rg), by the cold fusion between nickel ions and a bismuth target in a linear accelerator:
In 2001, the IUPAC/IUPAP Joint Working Party (JWP) concluded that there was insufficient evidence for the discovery at...
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