Nickel-62

Nickel-62 is an isotope of nickel having 28 protons and 34 neutrons.

It is a stable isotope, with the highest binding energy per nucleon of any known nuclide (8.7945 MeV). It is often stated that ⁵⁶Fe is the "most stable nucleus", but actually ⁵⁶Fe merely has the lowest mass per nucleon (not binding energy per nucleon) of all nuclides. The lower mass per nucleon in Fe-56 is enhanced by the fact that ⁵⁶Fe has 26/56 = 46.43% protons, while ⁶²Ni has only 28/62 = 45.16% protons, and the relatively larger fraction of light protons in ⁵⁶Fe lowers its mean mass-per-nucleon ratio in a way that has no effect on its binding energy.

The misconception of ⁵⁶Fe's high nuclear binding energy probably originated from astrophysics. During nucleosynthesis in stars the competition between photodisintegration and alpha capturing causes more ⁵⁶Ni to be produced than ⁶²Ni (⁵⁶Fe is produced later in the star's ejection shell as ⁵⁶Ni decays). The ⁵⁶Ni is the natural end product of silicon-burning at the end of a supernova's life and is the product of 14 alpha captures in the alpha process which builds more massive elements in steps of 4 nucleons, from carbon. This alpha process in supernovae burning ends here, because of the higher energy of zinc-60, which would be the next step, after addition of another "alpha" (or more properly termed, helium nucleus).