Isotopes of hassium

Hassium (₁₀₈Hs) is a synthetic element, and thus a standard atomic weight cannot be given. Like all synthetic elements, it has no stable isotopes. The first isotope to be synthesized was ²⁶⁵Hs in 1984. There are 13 known isotopes from ²⁶³Hs to ²⁷⁷Hs and 1–4 isomers. The most stable isotope of hassium cannot be determined based on existing data due to uncertainty that arises from the low number of measurements. The half-lives of ²⁶⁹Hs and ²⁷¹Hs are about 12 seconds, whereas that of ²⁷⁰Hs is about 7.6 seconds. It is also possible that ^277mHs is more stable than these, with its half-life likely being 130±100 seconds, but only one event of decay of this isotope has been registered as of 2016.