High Quality Content by WIKIPEDIA articles! Dubnium is a chemical element with the symbol Db and atomic number 105. This is a radioactive synthetic element whose most stable isotope is 268Db with a half life of 28 hours. This is the longest lived transactinide isotope and is a reflection of the stability of the Z = 108 and N = 162 closed shells and the effect of odd particles in nuclear decay. Chemistry experiments have provided sufficient evidence to confidently place dubnium in group 5 of the Periodic Table. Element 105 was first reported by Russian scientists, in 1968-1970 at the Joint Institute for Nuclear Research in Dubna, Russia. The 1968 work was based on the detection of correlated decays of element 105 to known daughter nuclei using the reaction 243Am(22Ne,xn). They reported a 9.40 MeV and a 9.70 MeV alpha-activity and assigned the decays to the isotopes 260105 or 261105.

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