Atomic Number: 95 Atomic Radius: 244 pm (Van der Waals)
Atomic Symbol: Am Melting Point: 1176 °C
Atomic Mass: 243 Boiling Point: 2011 °C
Electron Configuration:
[Rn] 7s2 5f7
Oxidation States: 6, 5, 4, 3, 0


(the Americas) Americium was the fourth transuranic element to be discovered; the isotope 241Am was identified by Seaborg, James, Morgan, and Ghiorso late in 1944 at the wartime metallurgical laboratory at the University of Chicago as the result of successive neutron capture reactions by plutonium isotopes in a nuclear reactor.



The luster of freshly prepared americium metal is white and more silvery than plutonium or neptunium prepared in the same manner. It appears to be more malleable than uranium or neptunium and tarnishes slowly in dry air at room temperature. Americium must be handled with great care to avoid personal contamination. The alpha activity from 241Am is about three times that of radium. When gram quantities of 241Am are handled, the intense gamma activity makes exposure a serious problem. 241Am has been used as a portable source for gamma radiography. It has also been used as a radioactive glass thickness gauge for the flat glass industry and as a source of ionization for smoke detectors.


Los Alamos National Laboratory, Periodic Table of Elements,