Isotopes of copper

Copper (₂₉Cu) has two stable isotopes, ⁶³Cu and ⁶⁵Cu, along with 28 radioisotopes. The most stable radioisotope is ⁶⁷Cu with a half-life of 61.83 hours. Most of the others have half-lives under a minute. Unstable copper isotopes with atomic masses below 63 tend to undergo β⁺ decay, while isotopes with atomic masses above 65 tend to undergo β⁻ decay. ⁶⁴Cu decays by both β⁺ and β⁻.^[1]

There are at least 10 metastable isomers of copper, including two each for ⁷⁰Cu and ⁷⁵Cu. The most stable of these is ^68mCu with a half-life of 3.75 minutes. The least stable is ^75m2Cu with a half-life of 149 ns.^[1]