High Quality Content by WIKIPEDIA articles! In atomic physics, the principal quantum symbolized as n is the first of a set of quantum numbers (which includes: the principal quantum number, the azimuthal quantum number, the magnetic quantum number, and the spin quantum number) of an atomic orbital. There are a set of quantum numbers associated with the energy states of the atom. The four quantum numbers n, ?, m, and s specify the complete and unique quantum state of a single electron in an atom called its wavefunction or orbital.