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Isotopes of magnesium
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<p><a href="/facts/Magnesium/XyIhd2FG">Magnesium</a> (12Mg) naturally occurs in three stable isotopes: 24Mg, 25Mg, and 26Mg. There are 19 radioisotopes that have been discovered, ranging from 18Mg to 40Mg (with the exception of 39Mg). The longest-lived radioisotope is 28Mg with a half-life of 20.915(9) h. The lighter isotopes mostly decay to isotopes of <a href="/facts/Sodium/eYuSPu2V">sodium</a> while the heavier isotopes decay to isotopes of <a href="/facts/Aluminium/7wmR8jYE">aluminium</a>. The shortest-lived is <a href="/facts/Proton_drip_line/k3PfJUoy">proton-unbound</a> 18Mg with a half-life of 4.0(3.4) zeptoseconds. </p><p>A precise measurement of the neutron-rich 40Mg in 2019 showed the unexpected difference in its nuclear structure, compared to the lighter neighboring isotopes. </p>