fermium(redirected from Unnilnilium)
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n. Symbol Fm
A synthetic transuranic metallic element having over 20 isotopes and isomers with mass numbers ranging from 242 to 260. The longest-lived isotope has mass number 257 and a half-life of approximately 100 days. Atomic number 100; melting point 1527°C; valence 3. See Periodic Table.
[After Enrico Fermi.]
(Nuclear Physics) a transuranic element artificially produced by neutron bombardment of plutonium. Symbol: Fm; atomic no: 100; half-life of most stable isotope, 257Fm: 80 days (approx.)
[C20: named after Enrico Fermi]
fer•mi•um(ˈfɜr mi əm, ˈfɛər-)
a transuranic element, artificially produced from plutonium or uranium. Symbol: Fm; at. no.: 100.
Symbol Fm A synthetic, radioactive metallic element of the actinide series that is produced from plutonium or uranium. Its most stable isotope has a half-life of about 100 days. Atomic number 100. See Periodic Table.
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|Noun||1.||fermium - a radioactive transuranic metallic element produced by bombarding plutonium with neutrons|