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copernicium

copernicium, artificially produced radioactive chemical element; symbol Cn; at. no. 112; mass number of most stable isotope 285; m.p., b.p., sp. gr., and valence unknown. Situated in Group 12 of the periodic table , it is expected to have properties similar to those of zinc , cadmium , and mercury .

In 1996 an international research team led by Peter Armbruster and Sigurd Hofmann at the Institute for Heavy Ion Research at Darmstadt, Germany bombarded lead-208 atoms with high-energy zinc-70 ions. In a two-week experiment, one of the resulting atoms was unambiguously identified as an isotope of element 112 with mass number 277 and a half-life of 280 msec. In 2009 the name copernicium, for Copernicus , was proposed for the element by its discoverers, and International Union of Pure and Applied Chemistry (IUPAC) approved the name in 2010. The most stable isotope, copernicium-285, has a half-life of approximately 29 sec.

See also synthetic elements ; transactinide elements ; transuranium elements .

The Columbia Electronic Encyclopedia, 6th ed. Copyright © 2012, Columbia University Press. All rights reserved.

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