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Astatine, named from the Greek for "unstable", was discovered in
1940. It was first synthesized by bombarding bismuth (209Bi) atoms
with helium nuclei (4He, high-energy alpha particles). Sufficient quantities
were obtained so that some of its properties can be studied. However, a cyclotron
must be used to synthesize astatine. So, this makes it very expensive and limits
its application and study.
All isotopes of astatine are radioactive. About 20 isotopes are known, the
longest-lived being 210At with a half-life of 8.3 hours and decays
mainly by electron capture. Shown above
is a recording of the detection of astatine in the notebook of its discoverer,
D. R. Corson, an American physicist.
