Am

Americium

Identification

CAS Number: 7440-35-9

Discovery Year: 1945

Discoverer: G.T.Seaborg, R.A.James, L.O.Morgan, A.Ghiorso

Discovery Location: United States

Properties

Atomic Mass: 243 →Density: 12 g/cm³ →

Atomic Dimensions

Atomic Radius: 175 pm →

Atomic Radius (Rahm): 276 pm

Covalent Radius: 180 pm →

Van der Waals Radius: 244 pm

Atomic Volume: 20.8 cm³/mol

Thermodynamics

Melting Point: 1267 K →Boiling Point: 2880 K →Heat of Fusion: 10 kJ/mol →Heat of Vaporization: 238.5 kJ/mol →

Heat of Formation: 284 kJ/mol

Electronic Structure

Electron Config: [Rn] 5f7 7s2

Block: f

Period: 7 →

Oxidation States: +3, +4, +5, +6

Abundance & Geochemistry

Goldschmidt Class: synthetic

About

Radioactive metallic transuranic element, belongs to the actinoids. Ten known isotopes. Am-243 is the most stable isotope, with a half-life of 7.95*10^3 years. Discovered by Glenn T. Seaborg and associates in 1945, it was obtained by bombarding Uranium-238 with alpha particles.

Isotopes

Am-241 241 ☢ 433 a

Am-243 243 ☢ 7.37e+3 a