So if we look at the second column, let's look at copper. Now copper, if we're to look at the periodic table, we'd initially think it's argon 4S23D9. But if we look at the three D9 orbitals, what we should notice is we just need one more electron here and it will be completely filled. Remember, there's this need, this drive by your P&D sub levels or subshells to be either half filled or totally filled.
So we're going to say here an electron, an S orbital electron can be promoted to create completely filled orbitals with D9 elements. Here copper is a D9 element. It ends with D9. If you could just get one more electron, it can become D10 and that's what's going to happen. We take one from the S orbital before S orbital and we donate it over to the D. Doing this now we only have one electron here within 4 S and this now becomes totally filled in and therefore more stable.
So now this is 4S13 D10. So just remember we have the six elements we discussed previously in the videos. They have this drive where we're going to take one electron from an S orbital and promote it to one of the D orbitals so that we can create either 1/2 build D orbitals or totally filled, completely filled D orbitals. Remember this driving force that causes the exceptions within these neutral elements.