The Element Americium
Atomic Number: 95
Atomic Weight: 243
Melting Point: 1449 K (1176°C or 2149°F)
Boiling Point: 2284 K (2011°C or 3652°F)
Density: 13.69 grams per cubic centimeter
Phase at Room Temperature: Solid
Element Classification: Metal
Period Number: 7
Group Number: none
Group Name: Actinide
Special Notes: Radioactive and Artificially Produced
What's in a name? Named for the Americas.
Say what? Americium is pronounced as am-er-ISH-ee-em.
History and Uses:
Americium was discovered in 1944 by the American scientists Glenn T. Seaborg, Ralph A. James, Leon O. Morgan and Albert Ghiorso. They produced americium by bombarding plutonium-239, an isotope of plutonium, with high energy neutrons. This formed plutonium-240, which was itself bombarded with neutrons. The plutonium-240 changed into plutonium-241, which then decayed into americium-241 through beta decay. This work was carried out at the University of Chicago's Metallurgical Laboratory, now known as Argonne National Laboratory.
Americium can be produced in kilogram quantities and has a few practical uses. It is used in smoke detectors and can be used as a portable source of gamma rays. Americium-241, with a half-life of 432.2 years, is used in these products because it is easier to produce relatively pure samples of this isotope.
Estimated Crustal Abundance: Not Applicable
Estimated Oceanic Abundance: Not Applicable
Number of Stable Isotopes: 0 (View all isotope data)
Ionization Energy: 5.993 eV
Oxidation States: +6, +5, +4, +3
3s2 3p6 3d10
4s2 4p6 4d10 4f14
5s2 5p6 5d10 5f7