So that's what the poly exclusion principle tells us. And that means since any given orbital can have a maximum of two electrons there are two possible spin numbers or quantum spin numbers plus one two and minus one two. So I want to mention briefly two more important notes about quantum numbers. Now, to find a total number of orbitals in any given shell level with any given principal quantum number we simply take that principal quantum number and square it. So for N equals one there are one squared to one orbital. And that makes sense because when N equals one L equals zero and we have only the S orbital.