Nuclei with certain numbers of neutrons and protons (the magic numbers 2, 8, 20, 28, 50, 82, 126, ...) are particularly stable, because their shells are filled.
Tuumad, milles on kindel arv neutroneid ja prootoneid (maagilised arvud 2, 8, 20, 28, 50, 82, 126, …), on eriti stabiilsed, kuna nende kihid on täidetud.