Isotopes of fermium

<p><a href="/facts/Fermium/Us3rnvG5">Fermium</a> (100Fm) is a <a href="/facts/Synthetic_element/azU9Nr1m">synthetic element</a>, and thus a <a href="/facts/Standard_atomic_weight/8arqbQsq">standard atomic weight</a> cannot be given. Like all artificial elements, it has no <a href="/facts/Stable_isotope/vgcdxgjA">stable isotopes</a>. The first <a href="/facts/Isotope/KD9B1y6o">isotope</a> to be discovered (in <a href="/facts/Fallout/I1kJkLKt">fallout</a> from <a href="/facts/Nuclear_testing/s2srGDFP">nuclear testing</a>) was 255Fm in 1952. 250Fm was independently synthesized shortly after the discovery of 255Fm. There are 20 known <a href="/facts/Radioisotope/5WpCfbdq">radioisotopes</a> ranging in <a href="/facts/Atomic_mass/J1FJY9MV">atomic mass</a> from 241Fm to 260Fm (260Fm is unconfirmed), and 4 <a href="/facts/Nuclear_isomer/L8DHcqnk">nuclear isomers</a>, 247mFm, 250mFm, 251mFm, and 253mFm. The longest-lived isotope is 257Fm with a <a href="/facts/Half-life/kGVH8BAB">half-life</a> of 100.5 days, and the longest-lived isomer is 247mFm with a half-life of 5.1 seconds.
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Isotopes of fermium open-in-new

Isotopes of fermium