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Prior to the end of the Second World War, an American research team in Chicago discovered the 95th element on the periodic table – hence, the name "americium."
Americium is a radioactive metal that possesses an alpha activity approximately three times greater than that of radium. As a result, one of its isotopes, americium-241, serves as a portable source for gamma radiography. Americium is also used in crystallography research and as a source of neutrons.
Although the latter are rarely encountered in our daily lives, we are closer to this element than one might think. Many smoke detectors in North American homes and other buildings use americium as an ionization source to detect smoke from fires. Molecules not normally present in air are ionized by the alpha radiation emitted from americium, which "sets off" the alarm. Although americium is radioactive, it is present in such negligible amounts in smoke detectors that it is not considered to pose a hazard.