Is it ensure, insure, or assure?
|magic number |
Any of the numbers, 2, 8, 20, 28, 50, 82, or 126, that represent the number of neutrons or protons in strongly bound and exceptionally stable atomic nuclei. The existence of such stable nuclei is explained by assuming a shell structure for nucleons, much like the shell structure of electron orbitals around the nucleus.
in physics, in the shell models of both atomic and nuclear structure, any of a series of numbers that connote stable structure