Now, every orbital can have a maximum of two electrons. And what the Pole Exclusion Principle tells us is it states that any two electrons in any given atom can never have the same four quantum numbers. Remember, just like any car in any given state can only have one license plate one unique license plate any unique electron in any given atom will only have four quantum numbers unique to that electron. 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.