I am currently learning about Radioactivity and Nuclear Physics. Why are nuclides with an even number of protons and neutrons more stable?
I have read that nuclides with an even number of protons or neutrons or both, are more stable than those with an odd number of nucleons.
Is this something that is based on theoretical reasoning? Or just something taken from observation?
I understand that nuclides with more neutrons would be more stable due to more nuclear forces to act against the electrostatic repulsion between protons (to an extent), but I don't know why odd/even counts matter. Is there more stability due to possible greater symmetry if the nuclide has an even number of nucleons?
Related: What makes the number of neutrons the number of proton similar?