A transuranic, radioactive,
metallic element and member of the actinide
series. There are 18 known isotopes of americium,
the most stable of which is 243Am with a half-life
of 8.8 × 103 years. Americium is used in home smoke detectors
and in industrial density and thickness gauges; 241Am is a source
of gamma rays. Americium was first isolated
in 1944 by Glenn Seaborg, Leon Morgan, Ralph James, and Albert Ghiorso at
the University of Chicago. It is prepared by neutron
irradiation of plutonium.
| Sample of americium.