Fm

Fermium

Identification

CAS Number: 7440-72-4

Discovery Year: 1953

Discoverer: Argonne, Los Alamos, U of Calif

Discovery Location: United States

Properties

Atomic Mass: 257 →Density: 9.7 g/cm³ →

Atomic Dimensions

Van der Waals Radius: 245.00000000000003 pm

Thermodynamics

Melting Point: 1800 K →

Electronic Structure

Electron Config: [Rn] 5f12 7s2

Block: f

Period: 7 →

Oxidation States: +3

Abundance & Geochemistry

Goldschmidt Class: synthetic

About

Radioactive metallic transuranic element, belongs to the actinoids. Ten known isotopes, most stable is Fm-257 with a half-life of 10 days. First identified by Albert Ghiorso and associates in the debris of the first hydrogen-bomb explosion in 1952.

Isotopes

Fm-253 253 ☢ 3.00 d

Fm-257 257 ☢ 101 d