Specifications: Dubnium Dubnium is a chemical element in the periodic table that has the symbol Db and atomic number 105. This is a radioactive synthetic element whose most stable isotope is 268Db with a half life of 29 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.
