 Okay, so we're going to think about the atom calcium from the periodic table, and we're going to write out its full electron configuration, okay? So if you guys can help me, if you want, you don't have to, though, okay? So starting with the lowest energy level always, right, it's going to be 1S2. So how many electrons? This calcium have 20, right? So all of these numbers we want to add up to 20, right? So 1S2, 2S2, 2P6, 3S2, 3P6, 4S2, okay? So 2, 4, 10, 2, 4, 10, 10 plus 10 equals 20, so we got the right number, okay? So now we want to write the electron configuration, or we're going to draw the electron configuration by putting in the orbitals, okay? So the orbital diagram, I guess I should say. So how do we do that? We draw it starting lines, showing the energy levels and the different orbital subsets that are in that energy level, okay? So what's the lowest energy level orbital? How would I figure that out? Look over here, okay? So help me out. So what's the lowest energy orbital? 1S. 1S. So remember when I say 2, then I start referring to the electrons, so don't say that, okay? So what's the next, and how many orbitals are in the 1S? I already gave it away, but how many are there? One. One, right? How can I tell? Well, I can look here and I know that there's just two electrons there. Or really, what you should be doing is looking up at the periodic table and learn. So what's the next one up? And if you can't remember, it's up there. 2S. 2S. And how many orbitals are in it? One. One, very good. And the next one up? 3S. 3S. How many orbitals? One. One. Next one up? 3P. 3S. How many orbitals? One. One. Next one up? 3P. 3P. How many orbitals? Three. The next one up? 4S. 4S. How many orbitals? One. One. Okay? So this is increasing energy, right? And what do we know about these electrons? They like to go to the lowest energy orbital first, right? Okay, so we've got two electrons. So we're just going to put them in. But this tells us we've got two electrons in the 1S orbital. Is everybody okay with saying that? So how are they going to fill? So remember, Hunter Rule tells us that they like to go to the lowest energy level first. So 1 and then 2 is Pauli Exclusion Principle. The other one has to go opposite spin, right? So the next energy level is the 2S. So the first one goes there. The second one goes there. Like that. Okay. So the next one. Oh, sorry. Did I say Hunter Rule? I meant Off-Ball Principle Building Up. So the Hunter Rule is when you're building up doing a cross, right? So Hunter Rule now? One, two, three, Pauli Exclusion, four, five, six. Like that. Okay. So now Off-Ball, Pauli Exclusion, Off-Ball, Hunter Rule, Pauli Exclusion, and then Off-Ball, Pauli Exclusion. Right? So is everybody okay on doing something like that? So really what you should be able to do is if you can do this type of thing, this is really the most basic. This translates to this, okay? So your orbitals will always be set up in the same way here, okay? So the next one after the 4S would be the 3D, which would be starting with SC up there and going all the way to ZN, okay? And do one of those next if you want to, okay? Any questions on this one?