from The American Heritage® Dictionary of the English Language, 4th Edition

  • n. A synthetic transuranic metallic element (atomic number 100) having 10 isotopes with mass numbers ranging from 248 to 257 and corresponding half-lives ranging from 0.6 minutes to approximately 100 days. See Table at element.

from Wiktionary, Creative Commons Attribution/Share-Alike License

  • n. A transuranic chemical element (symbol Fm) with an atomic number of 100.

from the GNU version of the Collaborative International Dictionary of English

  • n. the transuranic element of atomic number 100; symbol Fm. The atomic weight of the most stable isotope, having a half-life of about 80 days, is 257. The first isotope, Fm255 was discovered in 1952 in the debris of a thermonuclear explosion. Other istopes have been produced in nuclear reactors and by decay of other transuranic elements.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

  • n. a radioactive transuranic metallic element produced by bombarding plutonium with neutrons


After Enrico Fermi.
(American Heritage® Dictionary of the English Language, Fourth Edition)
Named for Enrico Fermi. (Wiktionary)


  • The first glimpse at 112 lasted for only a third of a millisecond, until it decayed first into element 110 (darmstaditium) and then into four different short-lived elements until researchers lost its trail at element 110 (fermium).



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