Principal quantum numbers are denoted by the symbol 'n'. They designate the principal electron shell of the atom. The positive whole number values starting from 1,2,3 and so on..
Explanation:
All orbitals that have the same value of n are said to be in the same shell (level). For a hydrogen atom with n=1, the electron is in its ground state; if the electron is in the n=2 orbital, it is in an excited state. The total number of orbitals for a given n value is n2.
