We were just talking about constructive and destructive interference. We said that when things constructively interfere, they're going to create unusual regions of shared electron density. That's just another way of me saying higher probability called bonds. So remember that a bond is just an area where you wouldn't expect to find electrons. Usually, you would say, there shouldn't be electrons here according to the math. If I did the math, there should not be electrons. But for some reason, these orbitals are interfering with each other constructively, so they're increasing the chance of finding electrons there. Does that make sense? Cool.

So it turns out that there's actually multiple ways to make these bonds or these shared regions of electron density. So let's talk about the simplest ways first, which is the sigma bond. As you see here, I have sigma, sigma, sigma. First of all, what you should know is that sigma is going to be synonymous with the word single. So whenever I say a single bond, I'm always referring to a sigma bond. What that means is that a sigma bond is a region of one region of overlap. There's only one place where these orbitals are coming together and they're making that bond happen.

It turns out that there's actually several ways to make this region of overlap though. There are several ways to make a single bond. We could have an s orbital and an s orbital or we could have an s orbital and a p orbital, or we could have a p orbital and a p orbital. The important part is that they all count as sigma bonds as long as there's only one region of overlap. So those are all the different types of sigma bonds I could make.

Now, another type of bond that I could make is one that has more than one region of overlap. And that would be, for example, a pi bond. In fact, it would have 2 regions of overlap from 2 p orbitals coming together. As you can see, there's a region at the top. There's a region at the bottom. Just so you know, pi bonds are found in double bonds. So now, I'm going to clarify this in a little bit. Pi bond and double bond are not the same exact thing. What you should know is that a double bond has a pi bond in it. All right? Cool.