Ununpentium is the temporary name of a synthetic superheavy
element in the periodic table that has the temporary symbol Uup and
has the atomic number 115. It is placed as the heaviest member of
group 15 (VA) although a sufficiently stable isotope is not known
at this time that would allow chemical experiments to confirm its
position. It was first observed in 2003 and only about 30 atoms of
ununpentium have been synthesized to date, with just 4 direct
decays of the parent element having been detected. Four consecutive
isotopes are currently known, 287-290Uup, with
289Uup having the longest measured half-life of ~220 ms,
although the isotope 290Uup may well have an even longer
half-life (only a single decay has been measured leading to poor
accuracy).
On February 2, 2004, synthesis of ununpentium was reported in
Physical Review C by a team composed of Russian scientists at the
Joint Institute for Nuclear Research in Dubna, and American
scientists at the Lawrence Livermore National Laboratory. The team
reported that they bombarded americium-243 with calcium-48 ions to
produce four atoms of ununpentium. These atoms, they report,
decayed by emission of alpha-particles to ununtrium in
approximately 100 milliseconds.
The Dubna-Livermore collaboration has strengthened their claim
for the discovery of ununpentium by conducting chemical experiments
on the decay daughter 268Db. In experiments in June 2004
and December 2005, the Dubnium isotope was successfully identified
by milking the Db fraction and measuring any SF activities. Both
the half-life and decay mode were confirmed for the proposed
268Db which lends support to the assignment of Z=115 to
the parent nuclei.
Sergei Dmitriev from the Flerov Laboratory of Nuclear Reactions
(FLNR) in Dubna, Russia, has formally put forward their claim of
discovery of ununpentium to the Joint Working Party (JWP) from
IUPAC and IUPAP. The JWP are expected to publish their opinions on
such claims in the near future.
Ununpentium is historically known as eka-bismuth. Ununpentium is
a temporary IUPAC systematic element name. Research scientists
usually refer to the element simply as element 115.