Dubnium Information
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Dubnium Element
Dubnium is a synthetic chemical
element with the symbol Db and atomic number 105. Dubnium is highly
radioactive: the most stable known isotope, dubnium-268, has a half-life of
about 28 hours. This greatly limits the extent of research on dubnium.
Dubnium does not occur
naturally on Earth and is produced artificially. The Soviet Joint Institute for
Nuclear Research (JINR) claimed the first discovery of the element in 1968,
followed by the American Lawrence Berkeley Laboratory in 1970. Both teams
proposed their names for the new element and used them without formal approval.
The long-standing dispute was resolved in 1993 by an official investigation of
the discovery claims by the Transfermium Working Group, formed by the
International Union of Pure and Applied Chemistry and the International Union
of Pure and Applied Physics, resulting in credit for the discovery being
officially shared between both teams. The element was formally named dubnium in
1997 after the town of Dubna, the site of the JINR.
Theoretical research
establishes dubnium as a member of group 5 in the 6d series of transition
metals, placing it under vanadium, niobium, and tantalum. Dubnium should share
most properties, such as its valence electron configuration and having a
dominant +5 oxidation state, with the other group 5 elements, with a few
anomalies due to relativistic effects. A limited investigation of dubnium
chemistry has confirmed this. Solution chemistry experiments have revealed that
dubnium often behaves more like niobium rather than tantalum, breaking periodic
trends.
In 1970 a group of
investigators at the Lawrence Radiation Laboratory of the University of
California at Berkeley announced that they had synthesized isotope 260 of
element 105, whereupon they proposed the name hahnium for the element, in
honour of Otto Hahn, the discoverer of nuclear fission. The American team could
not duplicate the Soviet experiment; but, when its members bombarded
californium-249 with the nuclei of nitrogen-15 atoms, they produced
“hahnium-260,” which had a half-life of about 1.6 seconds. As further evidence
of their discovery, the scientists at Berkeley measured the amount of energy
emitted by “hahnium-260” as it decayed, as well as the elements produced in the
process; these characteristics were quite different from those of previously
known elements in the periodic system. The International Union of Pure and
Applied Chemistry ultimately determined that the element be named dubnium
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