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. 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.