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Known properties
Name, Symbol, NumberDubnium, Db, 105
Chemical series Transition metals
Group, Period, Block5, 7 , d
Appearance unknown; probably metallic,
silvery white or gray
Atomic weight [262] amu
Electron configuration probably [Rn]55f14 6d3 7s2
e- 's per energy level2, 8, 18, 32, 32, 11, 2
State of matter Presumably a solid

Dubnium is a chemical element in the periodic table that has the symbol Db and atomic number 105. This is a highly radioactive synthetic element whose most stable isotope has a half life of less than 40 seconds. This element therefore is not used for anything and little is known about its properties.


Dubnium (named after Dubna, Russia) was reportly first synthesized in early 1970 by Albert Ghiorso in Dubna, Russia. Later in 1970 researchers working at the University of California, Berkeley had positively identified element 105. The element was synthesized by bombarding a target californium-249 with a beam of 84 MeV nitrogen nuclei in particle accelerator. Atoms of element 105 were detected conclusively on March 5, 1970 but there is evidence that this element had already been formed at Berkeley a year earlier using the same method.

The Berkeley scientists later attempted to confirm the Soviet findings using more sophisticated methods but without success. They proposed that the new element should be named hahnium (symbol Ha) in honor of the late German scientist Otto Hahn (1879-1968). Consequently this was the name that most American and Western European scientists used.

An element naming controversy erupted over what to name this element after Russian researchers protested. The International Union of Pure and Applied Chemistry (IUPAC) thus adopted Unnilpentium (symbol Unp) as a temporary name for this element. However in 1997 they resolved the dispute and adopted the current name, Dubnium (symbol Db), after the city that contains the Russian Joint Institute for Nuclear Research.

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