 All right, so here's your how-to on orbital notation. To start orbital notation, the first thing you need is an electron configuration. To do an electron configuration, you need to have your orbitals in order from lowest energy to highest energy. So energy level 1 has nothing but an s orbital on it, so nothing but a 1s there. Level number 2 grows a little bit and has both s and p orbitals. So we have 2s and 2p. Level number 3 grows further still and has sps and d's. And 3s and 3p would be the next two orbitals in order. But we have to follow the off-bob principle in dealing with the d orbital. It says the d orbital can't be filled until the s orbital on the next level has. So we can't just jump to 3d. We have to do 4s and then come back to 3d. At which point that we can pick up where we left off, we have 4s, so the next one up is 4p. And the next one would be 4d. But again, the rule is we can't put anything in 4d until we've done 5s. Now according to the standards and what I understand, we can't go beyond atomic number 38, which is strontium. And that's where we did right there. 4 5s would be the last orbital in strontium atom. So there's really no need to go any further. So let's do a quick electron configuration. Let's do the electron configuration for a nice big one this time. Let's do it for selenium. Selenium is atomic number 34. That means it has 34 electrons for us to put in the electron configuration. So we just start at the beginning and work away across until we put 34 electrons away. So the 1s orbital can hold two electrons. All s orbitals can hold two electrons and no more. Next one up is 2s. It holds two electrons as well. Next one up is 2p. p orbitals can hold 6. And again, if you forget that, spdf. That's the order of orbitals. Just write down your odd numbers, 1, 3, 5, and 7. That's the number of suborbitals they have. And because your number of electrons multiply that by 2. So 2 in the s, 3 times 2, 6 in the p, 5 times 2, 10 in the d, 7 times 2, 14 in the f. So you ever forget your limits, just do that. 1, 3, 5, 7, 2, 6, 10, 14. Just double it all up. Back to what we're doing. 2 plus 2 is 4 plus 6 is 10. We have 10 of our 34. We still got 24 to go, so we've got a ways to go yet. Next one up is 3s. And again, an s holds 2. Next one up is 3p. A p holds 6. And then the next one up is 4s. It holds 2. Good time to see where we're at. See how close to that 34 we're getting. 2 plus 2 is 4. Plus 6 is 10. Plus 2 is 12. Plus 6 is 18. Plus 2 is 20. So we still have 14 more to go. So 3d is next. And d's hold 10. So that's 10 of our 14. We only have 4 left. 4p's the next orbital. And we can stick them all right in there. So that's the electron configuration for selenium. And the first level, we have an s orbital with 2. And the second level, we have an s orbital with p. And the second energy level, a p orbital with 6. Third energy level, s with 2. Third energy level, a p with 6. And the third energy level, a d with 10. Level number 4 has an s with 2. And a p with 4. As far as valence electrons are concerned, we have 4s2 and 4p6. That's my outermost energy level. 2 and 4 is 6, which makes sense because selenium isn't group 16. So there's a lot of ways to check yourself to make sure you've done these right. Add those all up and make sure they equal the number of electrons you're supposed to have. Check that valence electron thing to see if you've got the right number of valence electrons. There's a lot of ways to look at it to see if you've done it right. Now on to orbital notation. In orbital notation, we just want to draw this. We want to show what it looks like. Put little arrows in to represent the electrons. Show all the suborbital stuff like that. That's based on this right here. What you're going to do is you're going to draw a little blank. That blank represents your sublevel. And then you're going to put arrows on that blank that represent the electrons. One arrow going up, the other one going down to show that opposite spin that the poly exclusion principle says we have to have. S orbitals have one sublevel. So when you get to an S orbital, all you got to do is draw a little line and label it what orbital it is, 1s. This S orbital has two electrons in it. So an arrow going up and an arrow going down. Again, opposite spin. Next orbital is 2s. And again, the S orbital has one sublevel. So it's 2s. Again, two electrons. So one going up, the other going down. Now we've got a p orbital. There are three subopitals, three compartments, three rooms in the p orbitals. That's how we get that total of 6. There's three sublevels. So we draw in our three little lines, bracket it, and call it 2p, and get ready to put our electrons in. Now as a general rule, whenever you're doing p or d orbitals, whenever you have multiple sublevels, it's one electron in each suborbital first. And then you can go back and double them up. What that does is it means when we get to the end, if we have a partially filled orbital, we're going to have the minimum number of pairs, which is what it's all about. We want to minimize repulsion. That means the minimum number of pairs. So we do one in each sublevel. And then we come back and double them up. It's not going to be as big a deal here on the inside. Then when we get it to the end here, it's going to be really important. So that's 2p. Next one up is 3s. So again, s is just a single line. It's got 2 in it. Now another p orbital. 1, 2, 3 sublevels, call them 3p. Again, it's 6. One on each level, then double them up. 1, 2, 3, 4, 5, and 6. And again, this is just like stoichiometry. Do it the way I tell you to do it, and you won't mess it up. Start trying a shortcut, and that's when you're going to make mistakes. So after 3p is 4s, 4s is a single orbital. So just a single line, 2 electrons in it, 1 up, 1 down. And then the next one is d. 5 sublevels and a d orbital. So you've got it 5 lines. And call them 3d. And again, there's 10 in there, 1 on each line, then double them up. 1, 2, 3, 4, 5, 6, 7, 8, 9, and 10. Now we've reached the end. p orbital, 3 sublevels on 4p. Here's where it's really important. 1 per level, then double them up, because we're only going to put 4 in this time. And there's a way 4 has to look. Has to look like this. 1, 2, 3, 4, 1 double and 2 singles. That minimizes the number of doubles, which minimizes the repulsion, which means lowest energy state. And everything in the universe wants to be in its lowest energy state. So that is the orbital diagram for selenium. Granted, that's a huge one. But that is about as complicated as you get. There's really only four more elements beyond that that we would do. So that's about as tough as it come. Let's do a smaller one, just for the sake of doing a smaller one. Let's do phosphorus. Phosphorus is atomic number 15, so it has 15 electrons. So what we've got to do is do the electron configuration first. So back up to this, first orbital is a 1s. It can hold 2. 2 of the 15 down, 13 to go. Next orbital is 2s. As is hold 2, 4 down, 11 to go. Next orbital is 2p. P's can hold 6. 2 plus 2 is 4, plus 6 is 10. We still have 5 to go. Next orbital is 3s. We can stick 2 there. Now we're up to 12. We have three more to go, and all three fit in the 3p orbital. Again, total them up. 2 plus 2 is 4, plus 6 is 10, plus 2 is 12, plus 3 is 15. We've got the right number of electrons in there. You can check your valence electrons to make sure you did it right. Level 3 is our top most level. 2 plus 3 is 5. Phosphorus is in group 15. It's supposed to have 5. Three energy levels. I mean, there's a lot of ways to make sure that we're on the right track with this. Now it's time to draw it. We start with the 1s. That is a single blank. Label it 1s. Two electrons in it. One up, one down. Again, one blank because it is a single orbital. 2s. Single line again. Two electrons. One up, one down. Remember, the p is this collection of three sub orbitals. So three blanks. Fill it up one at a time until you get to 6. 1, 2, 3. Those are ups. Now we'll start doubling up the down arrows. 4, 5, 6. Next up is an s. Two electrons. One up and down. And finally the 3p. Three electrons. Again, one at a time and then you can double them up. That's it. All three are in there. All three are up. There's no downs to do this one. All singles, no repulsion. That's the way it needs to be. Minimum number of doubles.