Roentgenium was first observed in 1994 and several isotopes have
been synthesized since its first discovery. The most stable known
isotope is 281Rg with a half-life of ~20 seconds, which
decays by spontaneous fission, like many other N=170 isotones.
History
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 272Rg), by the cold fusion
between nickel ions and a bismuth target in a linear
accelerator:
20983Bi + 6428Ni -->
272111Rg + 10n
In 2001, the IUPAC/IUPAP Joint Working Party (JWP) concluded
that there was insufficient evidence for the discovery at that
time. The GSI team repeated their experiment in 2002 and detected a
further 3 atoms. In their 2003 report, the JWP decided that the GSI
team should be acknowledged as the discoverers.
Naming
The name roentgenium (Rg) was proposed by the GSI team in honor of
the German physicist Wilhelm Conrad Röntgen, and was accepted as a
permanent name on November 1, 2004. Previously the element was
known under the temporary IUPAC systematic element name unununium,
Uuu.
Chemistry
The heavier members of this group are well known for their lack of
reactivity or noble character. Silver and gold are both inert to
oxygen, but are attacked by the halogens. In addition, silver is
attacked by sulfur and hydrogen sulfide, highlighting its higher
reactivity compared to gold. Roentgenium is expected to be even
more noble than gold and can be expected to be inert to oxygen and
halogens. The most-likely reaction is with fluorine to form a
trifluoride, RgF3.
PERIODIC TABLE
Check out this interactive Periodic Table.
Check out this Roentgenium video. Prepared by The University of
Nottingham.