dubnium

Dubnium (Db) is a synthetic chemical element with atomic number 105. It is a transactinide element produced only in laboratories, and it has no stable isotopes. All known isotopes are radioactive and decay relatively quickly, which limits practical applications and makes detailed measurement difficult.

Dubnium was discovered independently by the Joint Institute for Nuclear Research in Dubna and by a team at Lawrence Berkeley National Laboratory in the late 1960s and early 1970s. Because both groups claimed discovery, the element's name was subject to dispute. In 1997, IUPAC officially adopted the name dubnium for element 105, in honor of the Dubna research center, with the symbol Db. The earlier proposed name hahnium is now obsolete.

Chemically, dubnium is expected to behave similarly to niobium and tantalum as a group 5 element. Theoretical and early experimental work has focused on the +5 oxidation state, though relativistic effects complicate its chemistry. Due to short half-lives and the tiny amounts produced, only a few chemical experiments have been performed.

Dubnium is produced in particle accelerators by fusion-evaporation reactions, typically involving actinide targets such as uranium, neptunium, or californium and light ions. The element is studied primarily to understand the chemistry and physics of transactinide elements and to test nuclear and chemical models.