noun Chemistry, Physics.
a transuranic element. Symbol: Fm; atomic number: 100.

1950–55; named after E. Fermi; see -ium

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World English Dictionary
fermium (ˈfɜːmɪəm)
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]

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Medical Dictionary

fermium fer·mi·um (fûr'mē-əm, fěr'-)
Symbol Fm
A synthetic radioactive metallic element whose most stable isotope is Fm 257 with a half-life of [approx] 100 days. Atomic number 100.

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American Heritage
Science Dictionary
fermium   (fûr'mē-əm)  Pronunciation Key 
Symbol Fm
A synthetic, radioactive metallic element of the actinide series that is produced from plutonium or uranium. Its most stable isotope is Fm 257 with a half-life of approximately 100 days. Atomic number 100. See Periodic Table.
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Encyclopedia Britannica


(Fm), synthetic chemical element of the actinoid series of the periodic table, atomic number 100. Fermium (as the isotope fermium-255) is produced by the intense neutron irradiation of uranium-238 and was first positively identified by Albert Ghiorso and coworkers at Berkeley, Calif., in debris taken from the first thermonuclear or hydrogen-bomb test explosion (November 1952), in the South Pacific. All fermium isotopes are radioactive. Mixtures of the isotopes fermium-254 (3.24-hour half-life), fermium-255 (20.1-hour half-life), fermium-256 (2.7-hour half-life), and fermium-257 (80-day half-life) can be produced by the intensive slow-neutron irradiation of elements of lower atomic number, such as plutonium.

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Encyclopedia Britannica, 2008. Encyclopedia Britannica Online.
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Example sentences
The elements curium, einsteinium, and fermium were named after famous nuclear physicists.
The chemical properties of fermium have been studied solely with tracer amounts.
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