Element:	Fermium
Symbol:	Fm
Atomic number:	100
Atomic weight:	[257]
Electron configuration:	[Rn] 5f12 7s2
Ground level:	3H6
Ionization potential:	6.5 ev
Physical form:	Metal
Melting point:	1527°C
Boiling point:
Critical temperature:
Density:
Specific heat:
Valence	3

Origin of name: after Enrico Fermi [1901–1954], nuclear physicist

Fermium, the eighth transuranium element of the actinide series to be discovered, was identified by Ghiorso and co-workers in 1952 in the debris from a thermonuclear explosion in the Pacific in work involving the University of California Radiation Laboratory, the Argonne National Laboratory, and the Los Alamos Scientific Laboratory. The isotope produced was the 20-hour ²⁵⁵Fm. During 1953 and early 1954, while discovery of elements 99 and 100 was withheld from publication for security reasons, a group from the Nobel Institute of Physics in Stockholm bombarded ²³⁸U with ¹⁶O ions, and isolated a 30-min α-emitter, which they ascribed to ²⁵⁰100, without claiming discovery of the element. This isotope has since been identified positively, and the 30-min half-life confirmed.

The chemical properties of fermium have been studied solely with tracer amounts, and in normal aqueous media only the (III) oxidation state appears to exist. The isotope ²⁵⁴Fm and heavier isotopes can be produced by intense neutron irradiation of lower elements such as plutonium by a process of successive neutron capture interspersed with beta decays until these mass numbers and atomic numbers are reached.

Twenty isotopes and isomers of fermium are known to exist. ²⁵⁷Fm, with a half-life of about 100.5 days, is the longest lived. ²⁵⁰Fm, with a half-life of 30 min, has been shown to be a product of decay of ²⁵⁴No. It was by chemical identification of ²⁵⁰Fm that production of Element 102 (nobelium) was confirmed.

Fermium probably has chemical properties resembling erbium.