Dubnium is a chemical element with symbol Db and atomic number 105. A transactinide element, dubnium is highly radioactive: the most stable known isotope, dubnium-268, has a half-life of just above a day. This greatly limits the extent of possible research on dubnium.
Dubnium does not occur naturally on Earth and is produced artificially. The first discovery of the element was claimed by the Soviet Joint Institute for Nuclear Research (JINR) in 1968, followed in 1970 by the American University of California. Both teams proposed a name for the new element, and used it without formal approval. The long-standing dispute was resolved in 1997, when the element was officially named dubnium after Dubna, the site of the JINR.
In the periodic table of the elements, dubnium is located in period 7, in d-block, thus being a transactinide element. Dubnium belongs to group 5 as the third member of the 6d series of transition metals. The limited investigation on chemistry of dubnium has demonstrated that behavior of dubnium is typical for group 5, and the element is established as the heavier homologue to tantalum in group 5; however, some deviations, particularly those from the periodic trends, occur due to relativistic effects....LESS