The orbital angular momentum quantum number in the nuclear shell model is not restricted by the principal quantum number as it is in the atomic shell model because the nuclear potential differs from the Coulomb potential. In the atomic model, energy levels correspond to the principal quantum number, following the relationship E ~ 1/n². However, in the nuclear shell model, the levels are defined in a central potential that does not adhere to this relationship. The numbers used in spectroscopic notation, like 1d or 2p, serve as serial identifiers rather than principal quantum numbers. Consequently, the principal quantum number does not correspond to energy in either the nuclear or atomic shell models.