| yooˌnənkwädˈēəm, artificially produced radioactive chemical element; symbol Uuq; at. no. 114; mass number of most stable isotope 289; m.p., b.p., sp. gr., and valence unknown. Situated in group IVA of the periodic table, it is expected to have properties similar to those of lead and tin. Late in Dec., 1998, using plutonium-244 and calcium-48 isotopes provided by the Lawrence Berkeley National Laboratory in Calif., Russian scientists employed a cyclotron at the Joint Institute for Nuclear Research in Dubna to produce an atom of element 114 with a mass number of 289. After a surprisingly long existence of 30 seconds, the ununquadium atom broke down successively into ununbium (element 112), darmstadtium (element 110), and hassium (element 108). The Dubna team created a second isotope of ununquadium, Uuq-287, with a half-life measured in milliseconds, three months later. Ununquadium is the first element of what might be an "island of stability" among heavy nuclei. Synthetic elements heavier than uranium are generally unstable. Scientists have for some time thought that elements number 114 and above might possess a very stable configuration of neutrons and protons because the nucleus would have a full complement of protons and neutrons making for longer life. The Dubna and Berkeley results seem to be evidence for this, since each isotope having an increasing number of neutrons (toward the optimum 184) has a longer half-life. No name has yet been suggested for element 114, which is therefore called ununquadium, from the Latin roots un for one and quad for four, 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. -48837- | 
