Fermium

History

• 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.

Properties

Isotopes

• 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).