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Dubnium ( formerly: Hahnium ) is an exclusively artificially produced chemical element with the element symbol Db and atomic number 105, it is one of the Transactinoiden. All Dubnium isotopes are radioactive.


Was discovered in 1967 by GN Flerov Dubnium et al. at the Joint Institute for Nuclear Research, Dubna at near Moscow and Albert Ghiorso et al. at the University of California, Berkeley. Like all transactinides Dubnium is exclusively synthesized by particle bombardment. The Russian working group worked here with the bombardment of americium by neon cores and suggested for the name Nielsbohrium ago:

The American team, however bombarded californium and berkelium with nitrogen and oxygen nuclei and gave the resulting element name Hahnium:

After a Elementnamensgebungskontroverse it was named after the Russian nuclear research center in Dubna in 1997. Other names were sometimes used for this element were:

  • Unnilpentium ( element symbol Unp ), ( systematic name, provisional name)
  • Eka- tantalum ( " standing under the tantalum ", provisional name)
  • Hahnium ( element symbol Ha ), ( after Otto Hahn )
  • Joliotium ( by Irène and Frédéric Joliot- Curie )


The item has been synthesized for research purposes only in very small amounts ( in the experiments by Albert Ghiorso et al. Emerged, eg, about 6 atoms per hour) and also has no meaning.


Classifications according to the Hazardous Substances Ordinance are not available because they only include the chemical danger and play a very minor role compared to the risks based on the radioactivity. Even the latter applies only if there is a relevant material for this amount.