It says that electrons will not go into an occupied orbital occupied by some electron until all the orbitals within that subshell are already filled. So, for example, let's look at the electron configuration of nitrogen. And it's the following two electrons are placed into the one s orbital. Two electrons are placed into the two s orbital, right? We're not placing three electrons into our s orbital or four electrons, because only a maximum of two electrons can go into any given orbital because of this principle that we mentioned above. Now, let's look at our p orbitals.