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Isotopes of einsteinium
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<p><a href="/facts/Einsteinium/RePoIVN9">Einsteinium</a> (99Es) 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 synthetic 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/Nuclear_fallout/I1kJkLKt">nuclear fallout</a> from the <a href="/facts/Ivy_Mike/yFqF9H72">Ivy Mike</a> <a href="/facts/Thermonuclear_weapon/T9zFe3H0">H-bomb</a> <a href="/facts/Nuclear_testing/s2srGDFP">test</a>) was 253Es in 1952. There are 18 known <a href="/facts/Radioisotope/5WpCfbdq">radioisotopes</a> from 240Es to 257Es, and 4 <a href="/facts/Nuclear_isomer/L8DHcqnk">nuclear isomers</a>. The longest-lived isotope is 252Es with a <a href="/facts/Half-life/kGVH8BAB">half-life</a> of 471.7 days, or around 1.293 years. </p>