Isotopes of magnesium

Magnesium (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 sodium while the heavier isotopes decay to isotopes of aluminium.

The shortest-lived is proton-unbound 18Mg with a half-life of 4.0(3.4) zeptoseconds.

A precise measurement of the neutron-rich 40Mg in 2019 showed the unexpected difference in its nuclear structure, compared to the lighter neighboring isotopes.