Nobelium is an artificially produced radioactive element. It has an atomic number (number of protons) of 102. Its chemical symbol is No.
Chemists classify nobelium in the actinide group among the transuranium elements. For information on the position of nobelium on the periodic table, see the article Periodic table.
Scientists have discovered more than 10 isotopes of nobelium, forms of the element with the same number of protons but different numbers of neutrons. These isotopes have atomic mass numbers (total numbers of protons and neutrons) from about 250 to 260. The most stable isotope has a mass number of 259 and a half-life of 58 minutes—that is, due to radioactive decay, only half the atoms in a sample of isotope 259 would still be atoms of that isotope after 58 minutes.
In 1957, scientists at the Nobel Institute for Physics in Stockholm, Sweden, claimed that they had produced an element whose atomic number was 102. They proposed to name the element nobelium in honor of Swedish inventor Alfred Nobel. However, no other laboratory could confirm their claim.
In 1958, scientists at Lawrence Radiation Laboratory (now Lawrence Berkeley National Laboratory) in Berkeley, California, published the first in a series of claims that they had created element 102. The Berkeley scientists also proposed the name nobelium. The International Union of Pure and Applied Chemistry (IUPAC) accepted this name. The IUPAC is the recognized authority in crediting the discovery of elements and assigning names to them.
In the 1950’s and 1960’s, the Joint Institute for Nuclear Research (JINR) in Dubna, Russia, near Moscow, claimed that its scientists had discovered element 102. In 1986, the 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. In 1993, the IUPAC accepted the working group’s conclusion that the discovery of element 102 was first proved in 1966 at the JINR. The JINR scientists had bombarded americium, whose atomic number is 95, with nitrogen, which has an atomic number of 7.
