roentgenium

The Columbia Encyclopedia, 6th ed. | 2011 | 700+ words | Copyright

roentgenium artificially produced radioactive chemical element; symbol Rg; at. no. 111; mass number of most stable isotope 272; m.p., b.p., sp. gr., and valence unknown. Situated in Group 11 of the periodic table , it is expected to have properties similar to those of gold .

In 1994 an international research team led by Peter Armbruster and Sigurd Hofmann at the Institute for Heavy Ion Research at Darmstadt, Germany bombarded bismuth-209 atoms with nickel-64 ions. In an 18-day experiment, three atoms were unambiguously identified as an isotope of element 111 with mass number 272 and a half-life of 1.5 msec. The discovery was officially confirmed in 2003, and the discoverers named the element in honor of Wilhelm Conrad Roentgen .

See also synthetic elements ; transactinide elements ; transuranium elements .

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