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Isotopes of mendelevium
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<p><a href="/facts/Mendelevium/bEHBu18F">Mendelevium</a> (101Md) 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 synthesized was 256Md (which was also the first isotope of any element produced one <a href="/facts/Atom/FoQ4kGN5">atom</a> at a time) in 1955. There are 17 known <a href="/facts/Radioisotope/5WpCfbdq">radioisotopes</a>, ranging in <a href="/facts/Atomic_mass/J1FJY9MV">atomic mass</a> from 244Md to 260Md, and 5 <a href="/facts/Nuclear_isomer/L8DHcqnk">isomers</a>. The longest-lived isotope is 258Md with a <a href="/facts/Half-life/kGVH8BAB">half-life</a> of 51.3 days, and the longest-lived isomer is 258mMd with a half-life of 57 minutes. </p>