Isotopes of manganese

Naturally occurring manganese (₂₅Mn) is composed of one stable isotope, Mn. Twenty-seven radioisotopes have been characterized, with the most stable being Mn with a half-life of 3.7 million years, Mn with a half-life of 312.08 days, and Mn with a half-life of 5.591 days. All of the remaining radioactive isotopes have half-lives that are less than 3 hours and the majority of these have half-lives that are less than a minute. This element also has seven meta states.

Manganese is part of the iron group of elements, which are thought to be synthesized in massive stars shortly before supernova explosions. Because of its relatively short half-life, Mn occurs on Earth only in tiny amounts due to the action of cosmic rays on iron in rocks.

As Mn decays to Cr, manganese isotopic analysis is typically combined with that of chromium and this has found application in isotope geology and radiometric dating. Mn−Cr isotopic ratios reinforce the evidence from Al and Pd for the early history of the Solar System. Variations in Cr/Cr and Mn/Cr ratios from several meteorites indicate a non-zero initial Mn/Mn ratio that implies Cr isotopic variations must result from in-situ decay of Mn in differentiated planetary bodies. Hence Mn provides additional evidence for nucleosynthetic processes shortly before coalescence of the Solar System.

The isotopes of manganese range from Mn to Mn. The primary decay mode before the most abundant stable isotope, Mn, is electron capture and the primary mode after is beta decay.