 It is often stated that 56Fe is the "most stable nucleus", but only because 56Fe has the lowest "mass" per nucleon (not binding energy per nucleon) of all nuclides.The lower mass per nucleon of 56Fe is possible because 56Fe has 26/56 = 46.43% protons, while 62Ni has only 28/62 = 45.16% protons; and the larger fraction of lighter protons in 56Fe lowers its mean mass-per-nucleon ratio, despite having a slightly higher binding energy in a way that has no effect on its binding energy.The high binding energy of nickel isotopes in general makes nickel an "end product" of many nuclear reactions (including neutron capture reactions) throughout the universe and accounts for the high relative abundance of nickel—although most of the nickel in space (and thus produced by supernova explosions) is nickel-58 (the most common isotope) and nickel-60 (the second-most), with the other stable isotopes (nickel-61, nickel-62, and nickel-64) being quite rare.