This element is no longer available.
Dubnium is highly radioactive: the most stable known isotope, dubnium-268, has a half-life of just over a day. This greatly limits the extent of 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 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 IUPAC/IUPAP Joint Working Party, resulting in credit for discovery being officially shared between both teams. The element was officially named dubnium in 1997 after the town of Dubna, the site of the JINR.
In the periodic table of the elements, dubnium is located in group 5 as the third member of the 6d series of transition metals. Limited investigation of dubnium chemistry has demonstrated that dubnium behaves as a typical group 5 element and the heavier homologue to tantalum; however, some deviations from periodic trends occur due to relativistic effects.