Dubnium

Dubnium is the superheavy element with atomic number 105, synthesized between the late 1960s and early 1970s by teams in Dubna, USSR, and Berkeley, U.S., who bombarded suitable targets with heavy ions. All of its isotopes have half-lives of only tens of seconds to tens of minutes, it does not occur in nature, and only a few atoms at a time can be produced in heavy-ion accelerators. It has no practical uses and serves only in research on the nuclear chemistry and nuclear structure of superheavy elements.

Dubnium compounds such as dubnium bromide and dubnium oxychloride have only been briefly observed in single-atom on-line chemistry experiments, to judge whether it behaves like tantalum and niobium; they have never been prepared in macroscopic quantities and have no scale of application.