<P> The principal quantum number is related to the radial quantum number, n, by: </P> <Dl> <Dd> n = n r + l + 1 (\ displaystyle n = n_ (r) + \ ell + 1 \,) </Dd> </Dl> <Dd> n = n r + l + 1 (\ displaystyle n = n_ (r) + \ ell + 1 \,) </Dd> <P> where l is the azimuthal quantum number and n is equal to the number of nodes in the radial wavefunction </P>

How may orbitals are there in a shell of principal quantum number n