Bismuth has no stable isotopes, but does have one very long-lived isotope; thus, the standard atomic weight can be given as 208.98040(1).

Is bismuth stable or unstable?

Bismuth was long considered the element with the highest atomic mass that is stable, but in 2003 it was discovered to be extremely weakly radioactive: its only primordial isotope, bismuth-209, decays via alpha decay with a half-life more than a billion times the estimated age of the universe.

Is lead-214 stable?

Uranium is widely distrib- uted in rocks and soils throughout the earth’s crust. … Thus, radium-226 is one of the decay products of uranium-238. Polonium-218 and lead-214 are decay products of radon-222. The final isotope, lead-206, is stable (non-radioactive) and its formation ends the series.