<s>[INST] What's the half life of a helium 6 isotope? [/INST] Helium-6 has a half life of 0.8 seconds. It decays by emitting a beta particle.</s>\ <s>[INST] What element has the highest half life? [/INST] Elements don't have half-lives, isotopes of elements have.

Stable isotopes have an infinite half-life.

Certain isotopes of elements, such as isotopes of tin (Sn) are suspected to be radioactive, but their expected half-life is so great that no decay has been observed yet. Isotopes whose half-life is greater than the age of the universe can be considered, for all practical purposes, stable.</s>