Polonium (
Po) has 33
isotopes, all of which are
radioactive, with between 186 and 227 nucleons.
210Po with a
half-life of 138.376 days has the longest half-life of naturally occurring polonium.
209Po with a half-life of 125 years has the longest half-life of all
isotopes of polonium.
209Po and
208Po (half-life 2.9 years) can be made through the alpha, proton, or deuteron bombardment of
lead or
bismuth in a
cyclotron.