All right. So remember that I said that we can move electrons as long as we're not breaking octets. Okay. We can't break octets. We can't have more than 8 electrons. So, in this case, I really only have one set of electrons that has my attention. We always want to start with the most negative thing, and that would be my lone pair because my lone pair is just these free electrons. So, if I were to move these electrons and make them into a double bond, would that be okay? Would I be breaking the octets? Actually, I would be if I just left it like that. Because remember, this carbon here already has a hydrogen. So if I made that double bond, I would now have 5 bonds to that carbon; that would suck.
So, can you guys see anything that I could do to fix that? What I could do is break a bond. So I could break this double bond and put those 2 electrons. Remember that there are 2 electrons in that double bond? In the additional π bond, we could take those 2 electrons and make them into a lone pair. So what that means is that let's just go ahead and draw this as double-sided arrows since we're going to draw a new resonance structure. What I would get is something like this where I have an NH2 here, but now I have a double bond and now I have a lone pair here. But remember that with bond line structures, usually, we don't include a lot of lone pairs. We instead want to use formal charges. So let's compute the formal charges here. By the way, that H is still there. I just didn't draw it because H's can be implied. So what would be the formal charge of this carbon right here now? Well, it wants 4 electrons and how many does it have? 5. It has 5 valence electrons, so this is going to have a negative charge. So I'm just going to erase the lone pair and I'm just going to replace it with a negative because I think that's a little easier to look at. Now let's look at the nitrogen. Does that one have a formal charge? Well, nitrogen wants 5 electrons and it has 4, so kind of like they swapped. The nitrogen has a positive charge.
All right. So there we have it. That is a resonance structure. Is there anything else that could happen? I know that some of you guys are wondering, okay, but couldn't I do something else? Couldn't I, let's say, make this negative do a double bond there? Couldn't I do that? And the answer is no, you couldn't. That would be terrible. Please don't do that. The reason is that think about it. There are already 2 hydrogens here. If I went ahead and tried to make a double bond here, first of all, that carbon would now have 5 bonds. Secondly, there's nothing else that I can break to make that work. You can never break single bonds with resonance structures. So what that means is that I would have to either break off one of the H's or I would have to cut off this carbon-carbon bond, which would suck. So that negative charge is stuck. It can't go there. You say, oh, well, what if it goes down? How would it be if I put it down here? The same exact thing. Once again, I've got 2 H's, and by making a double bond, I would be forced to break off a hydrogen or break off a carbon. It would suck. So that negative charge is stuck there. The only other thing that it can do is it can go back in the direction it came from. So if I made a double bond there, then that would be fine because then I could break this bond and make it a lone pair there. See how this works? So you basically keep going with that charge until you get stuck. Until there's nothing else you can do. So those are my resonance structures for this compound. Cool?