Definition of fermium in English:



  • [mass noun] The chemical element of atomic number 100, a radioactive metal of the actinide series. Fermium does not occur naturally and was discovered in 1953 in the debris of the first hydrogen bomb explosion.

    • ‘The transfermium elements are those elements with atomic numbers greater than 100, the atomic number for fermium.’
    • ‘All isotopes of fermium are radioactive, with fermium-257 having the longest half life, 20.1 hours.’
    • ‘Scientists have for the first time literally shed light on properties of the radioactive element fermium - a metal discovered some 50 years ago.’
    • ‘The Dubna group had made fermium and rutherfordium this way in the 1970s.’


1950s: from the name of Fermi, Enrico + -ium.