Isotopes of molybdenum

Molybdenum (₄₂Mo) has seven isotopes in nature, with atomic masses of 92, 94-98, and 100. All are stable except ¹⁰⁰Mo, which undergoes double beta decay with a half-life of 7.07×10¹⁸ years (the shortest known for this mode) to ¹⁰⁰Ru. ⁹²Mo and ⁹⁸Mo are also energetically able to decay in this manner, to zirconium and ruthenium respectively; the others are theoretically stable. There are also a total of 32 synthetic isotopes known, and at least 13 metastable nuclear isomers, ranging in atomic mass from 81 to 119.

The isotopes with mass 93 or lower decay by electron capture or positron emission to niobium isotopes (or zirconium after delayed proton emission); those with mass 99 or higher by ordinary beta decay to technetium. The most stable of the former are ⁹³Mo, recently measured to have a half-life around 4800 years, and ⁹⁰Mo at 5.56 hours. The most stable of the latter is the medically important ⁹⁹Mo, half-life 65.932 hours, and whose decay leads to the chief isotope of technetium. By far the most stable isomer is ^93m1Mo at 6.85 hours, decaying to its ground state.