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 an extremely radioactive element; its most stable known isotope, ununpentium-289, has a half-life of only 220 milliseconds.[5] It is also known as eka-bismuth or simply element 115. Ununpentium was first created in 2003 by a team composed of Russian scientists at the Joint Institute for Nuclear Research (JINR) in Dubna, and American scientists at the Lawrence Livermore National Laboratory. In December 2015, it was recognized as a new element by the International Union of Pure and Applied Chemistry (IUPAC) and the International Union of Pure and Applied Physics (IUPAP). About 100 atoms of ununpentium have been observed to date, all of which have been shown to have mass numbers from 287 to 290.
In the periodic table, it is a p-block transactinide element. It is a member of the 7th period and is placed in group 15 as the heaviest pnictogen, although it has not been confirmed to behave as the heavier homologue to the pnictogen bismuth. Ununpentium is calculated to have some similar properties to its lighter homologues, nitrogen, phosphorus, arsenic, antimony, and bismuth, although it should also show several major differences from them.
Ununpentium is expected to be in the middle of an island of stability centered around copernicium (element 112) and flerovium (element 114): the reasons for the presence of this island are however still not well understood.[21][22] Due to the expected high fission barriers, any nucleus within this island of stability exclusively decays by alpha decay and perhaps some electron capture and beta decay.[2] Although the known isotopes of ununpentium do not actually have enough neutrons to be on the island of stability, they can be seen to approach the island as in general, the heavier isotopes are the longer-lived ones.[5][8]
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