Isotopes of dubnium

Dubnium (₁₀₅Db) is a synthetic element, thus a standard atomic weight cannot be given. Like all synthetic elements, it has no stable isotopes. The first isotope to be synthesized was ²⁶¹Db in 1968. Thirteen radioisotopes are known, ranging from ²⁵⁵Db to ²⁷⁰Db (except ²⁶⁴Db, ²⁶⁵Db, and ²⁶⁹Db), along with one isomer (^257mDb); two more isomers have been reported but are unconfirmed. The longest-lived known isotope is ²⁶⁸Db with a half-life of 16 hours.