| yooˌnŭnhĕkˈsēəm, artificially produced radioactive chemical element; symbol Uuh; at. no. 116; mass number of most stable isotope 289; m.p., b.p., sp. gr., and valence unknown. Situated in group VIA of the periodic table, it is expected to have properties similar to those of polonium and tellurium. In 1999 a research team at the Lawrence Berkeley National Laboratory in Calif. bombarded lead-208 atoms with high-energy krypton-86 ions to create, apparently, ununoctium (element 118) atoms. The Uuo-293 isotope that they synthesized emitted an alpha particle to decay into Uuh-289, which has a life-life of about 0.6 millisecond, which then emitted an alpha particle to decay into ununquadium (element 114). Although the Berkeley laboratory retracted its claim for creating ununoctium in 2001, other research teams have since created ununhexium directly. No name has yet been suggested for element 116, which is therefore called ununhexium, from the Latin roots un for one and hex for six, under a convention for neutral temporary names proposed by the International Union of Pure and Applied Chemistry (IUPAC) in 1980. See also synthetic elements; transactinide elements; transuranium elements. ____________________The Columbia Encyclopedia, Sixth Edition Copyright© 2004, Columbia University Press. Licensed from Lernout & Hauspie Speech Products N.V. All rights reserved. -48835- | 
