Hassium is an artificially produced radioactive element with 108 protons—that is, with an atomic number of 108. Scientists have discovered several different isotopes of hassium. Different isotopes of an element have the same number of protons but different numbers of neutrons. The most stable isotope of hassium has an atomic mass number (total number of protons and neutrons) of 263. This isotope has a half-life of 1 second—that is, due to radioactive decay, only half of the atoms in a sample of isotope 263 would still be atoms of that isotope after 1 second.
The chemical symbol for hassium is Hs. Chemists classify hassium in the transactinide element group among the transuranium elements . For information on the position of hassium on the periodic table, see the article Periodic table .
In 1984, scientists at the Heavy Ion Research Center in Darmstadt, West Germany (now part of Germany), announced the production of the element. They claimed that they had produced three atoms of it with mass number 265. They bombarded lead, whose atomic number is 82, with iron, which has an atomic number of 26.
Scientists at the Joint Institute for Nuclear Research in Dubna, near Moscow, made a rival claim in 1984. Dubna was then part of the Soviet Union and is now in Russia. The Dubna scientists also bombarded lead with iron.
In 1986, the International Union of Pure and Applied Chemistry (IUPAC) and the International Union of Pure and Applied Physics formed a working group to review the histories of the elements with atomic numbers from 101 to 109. IUPAC is the recognized authority in crediting the discovery of elements and assigning names to them. The working group concluded that, though the Soviets had probably produced the element, the West Germans deserved the credit for its discovery because their experiments were more detailed. The experiments at Darmstadt provided definitive evidence for the atomic number and atomic mass of isotopes of the element.
In 1993, IUPAC accepted the working group’s conclusion. Disagreements about what to name the element delayed an official naming until 1997, however. The name hassium comes from Hasse, Latin for Hesse, the German state where Darmstadt lies. Before the element got its official name, it was referred to as element 108.
