Now, what I want to do is switch gears and talk about a type of notation that's very common in organic chemistry, and it's a model that we use to really predict what molecular orbitals are going to look like. It's called the linear combination of atomic orbitals. So, if you ever see LCAO, that just means this little diagram that I have drawn right here. So let's go ahead and just get right into it, figure out what's going on. The first thing you need to do is learn how to read this. There are 2 orbitals on the sides, here and here. These are your atomic orbitals. Write in AO AO. Just so you know, these are the same types of orbitals that we were dealing with when we talked about atomic orbitals. Basically, just orbitals that have 2 electrons in them. They don't interfere with each other; those are just the orbitals by themselves with the atoms by themselves. Now, these orbitals in the middle have to do with interference. They have to do with how the atomic orbitals are coming together. These are called molecular orbitals. What molecular orbitals do is they predict where electrons are going to be in the entire molecule, not just for the atom. Does that make sense? Basically, they predict the way the bond is going to behave.
All right. So let's look at these three different possibilities of the way that atoms could interfere with each other, orbitals could interfere with each other. So let's go ahead and start with the simplest form of interference, which would be nonbonding. Now, I did not talk about nonbonding in the previous topic, so I want to ask you guys what do you think nonbonding is? Well, just like it sounds, it means that they're not bonding. It means they're not interfering with each other. So, you could almost think of it as I’m holding one hydrogen in one hand, one orbital in the other, one orbital in the other. They’re not interfering with each other. Maybe they’re too far apart or whatever, but they are just like freestanding. So, in that case, nonbonding, as you can see, I just have like a comma here. This means I have 2 orbitals that are not interacting and the way that I would draw these is as atomic orbitals because they don’t have any bond at all. So let's go ahead and try to figure out what the atomic orbitals would look like. What I want you guys to do is just pretend that this is a hydrogen atom and what type of orbital does a hydrogen atom have? Do you guys remember? Well, if you think about it, a hydrogen atom only has one electron, so that one electron should be in the 1s orbital. So that's why, as you've noticed, I have 1 and 1. What that means is that this is the 1s orbital for the a hydrogen and this is the 1s orbital for the b hydrogen. Does that make sense? I hope that's not too confusing. Basically, what I’m doing is I’m just going to map out where the electron is going to be for this atomic orbital and where the electron is going to be for this one.
So now that I know which orbitals correspond to which atoms, you guys have to tell me how many electrons do I have in the nonbonding orbitals. How many electrons do I have in each in 1s, a and in 1s, b. Well, what’s the atomic number of hydrogen? 1. So how many electrons should I have? 1. So what I’m going to do is I’m going to draw 1 electron here, 1 electron here. I’m done. That represents the one electron that’s in this orbital here and the one electron that’s in that orbital there. Does that make sense so far? I hope so. I know it's a little bit complicated. I’m trying to make it as easy as possible. So those are my atomic orbitals. Now remember that I said these orbitals in the middle, the molecular orbitals, have to do with how they’re interfering. So let's talk about the easiest form of interfering first, which is bonding.
Okay. So, remember that bonding would be a constructive interference. The way that you can constructive, go ahead and write down constructive. The constructive interference can be represented by just a positive, not a positive, a plus, meaning that one orbital is adding to another orbital and making the chances of finding an electron there better. The way that you would denote that on my model is that I would have this electron jump down to this energy state and this electron jump down to this energy state because now they're being shared between both atoms. So what I would have is that now one becomes an up spin and one becomes a down spin. The way that I’ve heard this as an analogy before is that imagine that these are like 2 people that are financially unstable and they can’t pay their bills and then they decide to move in together and share costs. So imagine you’re not cutting it and you’re like, hey let’s just go ahead and room for a few months or whatever. What that’s going to do is it’s going to make both of them more energetically favorable and I’m going to talk about that in a second. When they constructively overlap like this, that’s going to make what we call a sigma bond. Remember, a sigma bond is a region of one overlap. And the reason it’s called sigma-1s is because that’s the sigma bond created by 1s orbitals, 2 1s orbitals. All right. Cool. So hopefully that makes sense so far. That when they constructively interfere, you’re going to wind up filling what’s called the bonding orbital, which is this one right here. Now let’s see what happens when they destructively interfere. So let’s say that these 2 people try to move in together, but they just hate each other's guts. Well, that would be an anti bonding association where you use a minus charge to show that they're actually going to form a node in the middle and there's going to be no overlap at all. When that happens, these 2 electrons are actually going to jump up to a higher energy state and fill the antibonding orbital. The antibonding orbital, just so you know, is denoted by the star. If you ever see that star, that means this is antibonding. As you can see, these electrons are actually having to become see the energy is going up. They're actually having to become more energetic to do-[TRANSMISSION END]-