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Atomic Number:100Atomic Symbol:Fm
Atomic Weight:257Electron Configuration:2-8-18-32-30-8-2
Shells:2,8,18,32,30,8,2Filling Orbital:5f12
Melting Point:oCBoiling Point:oC
Description:Man made radioactive metal.


(Enrico Fermi)
  • Fermium, the eighth discovered transuranium element of the actinide series, was identified by Ghiorso and co-workers in 1952 in the debris from a thermonuclear explosion in the pacific during work involving the University of California Radiation Laboratory, Argonne National Laboratory, and 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 alpha-emitter, which they ascribed to 250-100, 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. In normal aqueous media, only the (III) oxidation state appears to exist.


  • 254Fm and heavier isotopes can be produced by intense neutron irradiation of lower elements, such as plutonium, using a process of successive neutron capture interspersed with beta decays until these mass numbers and atomic numbers are reached.
  • Sixteen isotopes 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 minutes, has been shown to be a decay product of element 254-102. Chemical identification of 250Fm confirmed the production of element 102 (nobelium).

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