Numbers of neutrons or protons that occur in atomic nuclei to produce very stable structures. The magic numbers for both protons and neutrons are 2, 8, 20, 28, 50, and 82. For neutrons 126 and 184 are also magic numbers and for protons 114 is a magic number. The relationship between stability and magic numbers led to a nuclear shell model in analogy to the electron shell model of the atom. The term ‘magic number’ is also used to describe the number of atoms in particularly stable cluster molecules, such as the 60 carbon atoms of buckminsterfullerene.