Americium

Americium (pronounced /ˌæməˈrɪsiəm/, AM-ə-RIS-ee-əm) is a synthetic element that has the symbol Am and atomic number 95. A radioactive metallic element, americium is an actinide that was obtained in 1944 by Glenn T. Seaborg who was bombarding plutonium with neutrons and was the fourth transuranic element to be discovered. It was named for the Americas, by analogy with europium. Americium is widely used in commercial ionization chamber smoke detec... more

Americium (pronounced /ˌæməˈrɪsiəm/, AM-ə-RIS-ee-əm) is a synthetic element that has the symbol Am and atomic number 95. A radioactive metallic element, americium is an actinide that was obtained in 1944 by Glenn T. Seaborg who was bombarding plutonium with neutrons and was the fourth transuranic element to be discovered. It was named for the Americas, by analogy with europium. Americium is widely used in commercial ionization chamber smoke detectors, as well as in neutron sources and industrial gauges. Pure americium has a silvery and white luster. At room temperature it slowly tarnishes in dry air. It is more silvery than plutonium or neptunium and apparently more malleable than neptunium or uranium. Alpha emission from Am is approximately three times that of radium. Am emits intense gamma rays, creating a serious exposure problem for anyone handling gram quantities of the element. Americium is also fissile; the critical mass for an unreflected sphere of Am is approximately 60... less