Polonium in the Earth's crust are not harmful. Polonium has been found in tobacco smoke from tobacco leaves grown with phosphate fertilizers. Because it is present in small concentrations, isolation of polonium from natural sources is a tedious process. The largest batch of the element ever extracted, performed in the first half of the 20th century, contained only (9 mg) of polonium-210 and was obtained by processing 37 tonnes of residues from radium production. Polonium is now usually obtained by irradiating bismuth with high-energy neutrons or protons. In 1934, an experiment showed that when natural Bi is bombarded with neutrons, Bi
Isotopes of polonium Isotopes of polonium Polonium (Po) has 33 isotopes, all of which are radioactive, with between 186 and 227 nucleons. Po with a half-life of 138.376 days has the longest half-life of naturally occurring polonium. Po with a half-life of 125 years has the longest half-life of all isotopes of polonium. Po and Po (half-life 2.9 years) can be made through the alpha, proton, or deuteron bombardment of lead or bismuth in a cyclotron. Po is an alpha emitter that has a half-life of 138.376 days; it decays directly to stable Pb. A milligram of Po emits as many alpha particles