Overview

Americium was synthesised in 1944 at the wartime Metallurgical Laboratory in Chicago by Glenn Seaborg, Ralph James, Leon Morgan and Albert Ghiorso, by bombarding plutonium with neutrons. It was named after the Americas, the continent of its discovery. Americium is a silvery, radioactive metal, and, remarkably for so exotic an element, it is put to everyday use: a tiny amount of americium-241 provides the ionising source in most household smoke detectors. The steady alpha particles from a speck of the isotope ionise the air in the detector so that drifting smoke disturbs the current and sounds the alarm, and americium also serves in the industrial gauges that measure the thickness and density of materials.

Americium's existence was first revealed to the public not in a scientific journal but on the radio: in November 1945, Glenn Seaborg announced the discovery of both americium and curium live on the popular children's quiz programme Quiz Kids, after one young panellist asked whether any new elements had been found, a disclosure that reportedly startled his own laboratory colleagues, who had expected the formal scientific announcement to come first. Wartime secrecy had kept both elements classified for over a year before that broadcast, so the news reached the general public before it reached most of the scientific community in print.