Nucleons in nuclei pair up in spin up/down pairs similarly to electrons in orbitals (because they're fermions). So the most stable nuclei usually have
even numbers of nucleons, and with the exception of lithium-6, boron-10 and nitrogen-14, it is basically always more stable to have an even number of
protons with an even number of neutrons than a maybe more favorable proton/neutron ratio with odd numbers of both. |