Copernicium is an artificially produced radioactive element . It is also known as element 112 because it has an atomic number (number of protons) of 112. By late 2002, scientists had reported the creation of 10 atoms of the element. In 2009, the International Union of Pure and Applied Chemistry (IUPAC) began the process of approving a name for element 112. The Heavy Ion Research Center in Darmstadt, Germany—which is credited with the discovery—proposed the name copernicium, in honor of the Polish astronomer Nicolaus Copernicus . IUPAC is the recognized authority in crediting the discovery of elements and assigning names to them.
The chemical symbol for copernicium is Cn. Chemists place copernicium in the transactinide group of transuranium elements . For information on the position of copernicium on the periodic table, see the article Periodic table .
An international group of scientists working at the Heavy Ion Research Center in Darmstadt, Germany, made the first claim in 1996. They said that they had created two atoms of copernicium. They produced the atoms in a device known as a particle accelerator (see Particle accelerator ). They bombarded lead, which has an atomic number of 82, with zinc, whose atomic number is 30. The resulting isotope had an atomic mass number of 277.
The scientists claimed that they produced four isotopes of copernicium. The isotopes of an element have the same number of protons but different numbers of neutrons. The atomic mass numbers (total numbers of protons and neutrons) of the copernicium isotopes were 277, 283, 284, and 285.
The researchers estimated that the half-life of isotope 277 is 0.00024 second—that is, due to radioactive decay, only half the atoms in a sample of isotope 277 would still be atoms of that isotope after 0.00024 second. To determine an isotope’s half-life with much accuracy, scientists must study many atoms of the isotope. When only a small number of atoms have been detected—as in the case of this particular isotope—they can obtain only an approximate value of the half-life.
In 1998, Russian and American scientists working at the Joint Institute for Nuclear Research in Dubna, Russia, near Moscow, also announced the production of two atoms of copernicium. Those atoms had an atomic mass number of 283. The researchers used a particle accelerator to bombard uranium, which has an atomic number of 92, with calcium, whose atomic number is 20. They estimated a half-life of about 100 seconds for isotope 283.
From 1999 to 2001, scientists reported further evidence for the creation of copernicium at Dubna. That evidence was the result of successful attempts to produce atoms of elements with atomic numbers of 114 and 116. See Flerovium ; Livermorium .
The researchers created five atoms of element 114 that had an atomic mass number of 288. Each atom decayed by emitting (giving off) an alpha particle, which consisted of two protons and two neutrons. As a result of the decay, the five atoms became atoms of copernicium with an atomic mass number of 284.
The scientists also created one atom of element 114 with an atomic mass number of 289. That atom emitted an alpha particle, thereby becoming an atom of copernicium with an atomic mass number of 285.
