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Known properties
Name, Symbol, NumberSeaborgium, Sg, 106
Chemical series Transition metals
Group, Period, Block15, 5 , d
Appearance unknown; probably metallic,
silvery white or gray
Atomic weight [266] amu
Electron configuration probably [Rn]55f14 6d4 7s2
e- 's per energy level2, 8, 18, 32, 32, 12, 2
State of matter Presumably a solid

Seaborgium is a chemical element in the periodic table that has the symbol Sg and atomic number 106. It was also known as "unnilhexium" (Unh), and at one time "rutherfordium" was suggested. Seaborgium is a synthetic element whose most stable isotope 266Sg has a half-life of 30 seconds.


Element 106 was discovered almost simultaneously by two different laboratories. In June 1974, a Soviet team led by G. N. Flerov at the Joint Institute for Nuclear Research at Dubna reported producing an isotope with mass number 259 and a half-life of 7ms, and in September 1974, an Americann research team led by Albert Ghiorso at the Lawrence Radiation Laboratory at the University of California, Berkeley reported creating an isotope with mass number 263 and a half-life of 0.9s.

Because their work was independently confirmed first, the Americans suggested the name seaborgium to honor the American chemist Glenn T. Seaborg. This name was extremely controversial because Seaborg was still alive. An international committee decided in 1992 that the Berkeley and Dubna laboratories should share credit for the discovery.

An element naming controversy erupted and as a result IUPAC adopted Unnilhexium (symbol Unh) as a temporary name for this element. In 1994 a committee of IUPAC recommended that element 106 be named rutherfordium and adopted a rule that no element can be named after a living person. This ruling was fiercely objected to by the American Chemical Society. In 1997, as part of a compromise involving elements 104 to 108 the name seaborgium for element 106 was recognized internationally.

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