NOBELIUM

(No), synthetic chemical element of the actinide series in Group IIIb of the periodic table, atomic number 102. Not occurring in nature, nobelium (as the isotope nobelium-254) was discovered (April 1958) by Albert Ghiorso, T. Sikkeland, J.R. Walton, and Glenn T. Seaborg at the University of California, Berkeley, as a product of the bombardment of curium (atomic number 96) with carbon ions (atomic number 6) accelerated in a heavy-ion linear accelerator. An international team of scientists working at the Nobel Institute of Physics in Stockholm had claimed less than a year before that they had synthesized the same element, which they named nobelium (for Alfred Nobel); but experiments performed in the Soviet Union (at the I.V. Kurchatov Institute of Atomic Energy, Moscow, and at the Joint Institute for Nuclear Research in Dubna) and in the United States (University of California, Berkeley) failed to confirm the discovery. The Berkeley and Dubna teams have subsequently produced more than a half dozen isotopes of nobelium; nobelium-255 (three-minute half-life) is the stablest. Using traces of this isotope, radiochemists have shown nobelium to exist in aqueous solution in both the +2 and +3 oxidation states. The +2 state is very stable, an effect more pronounced than was anticipated in comparison with the homologous lanthanide element ytterbium (atomic number 70). For a discussion of the properties and applications of the actinide group, of which nobelium is a member, see actinide element. atomic number 102 stablest isotope 255 valence 2,3 electronic config. 2-8-18-32-32-8-2 or (Rn)5f 147s2