Magic Numbers

A further, more specific pattern in nuclear stability is captured by magic numbers. Nuclides whose proton count or whose neutron count equals one of the values 2, 8, 20, 28, 50, 82 or 126 are found to be unusually stable and unusually abundant in nature, compared with neighbouring nuclides that do not hit one of these numbers.

A nucleus that has a magic number of protons AND a magic number of neutrons at the same time is doubly stabilised. Lead-208 (208-82-Pb) is the standard example: it has 82 protons and 126 neutrons, both of which are magic numbers, which is part of why lead-208 is the heaviest known stable (non-radioactive) nuclide with an even simpler doubly-magic structure, and helps explain lead's broader presence at the end of several …