Now recall that an orbital can hold a maximum of two electrons that pair up with opposite spins. Remember the opposite spins is part of the Poly exclusion principle. Now we have 2 terms, paramagnetic versus diamagnetic. With paramagnetic this is one at least one electron in given orbitals is unpaired, and diamagnetic is when all electrons in given orbitals are paired.
We're going to realize that paramagnetic substances are also magnetic, meaning that they're influenced by a magnetic field. So if we take a look here, paramagnetic if we look we have an S orbital, all the electrons within that one orbital are paired up. But if we look at the P orbitals, we have this electron by itself in an orbital, so it's unpaired. And this one too. As long as you have one electron in an orbital by itself unpaired, it's paramagnetic.
For diamagnetic, if we look, all the electrons in the S orbital are paired up, and then all the electrons in the P orbitals are paired up. There's not one electron by itself within a given orbital, so this is what is meant by diamagnetic. So just keep this in mind when doing the electron configurations of either elements or ions. Paramagnetic elements and ions have at least one electron by itself in an orbital somewhere. Diamagnetic, every single orbital has two electrons in it. All of the electrons are therefore paired up.
