Hey, guys, In this new video, we're gonna take a look at structural formulas. So we're gonna say your typical organic molecule can be drawn in a few different ways. So if we take, for example, painting paintings formula is C five h 12 Now there are different ways we can draw it. The three major ways that we can talk about it is our structural formula in our structural formula. We show all the connections that each of the elements is making. We also call this our expanded formula expanded because we've blown it out where every single bond is shown. And remember, carbon is Tetra Valent, Tetra valent, meaning that carbon wants to make four bonds when it's neutral. So here, if you take a look, each carbon in the center is making four bonds in some way, either by making those bonds with hydrogen or with carbons around them. They're all making four bonds Now, here you can transition away from your structural formula toe what's called your condensed formula. So you're condensed formula. You basically just push the bonds back in around that central element. So if you take a look, this carbon here it is connected to 123 hydrogen. So it's a CH three group. So there goes our stage three groups, this carbon. Here it is connected toe 12 carbons. So it's a CH two group. This carbon here is connected to 12 It's also ch two. This carbon here is connected toe 12 It is also a ch two. And then finally, the carbon at the end is connected. Toe 123 hydrogen. That's why it's a CH three. So we go from the structural or expanded formula to the condensed formula when we push the bonds inward so everything's compact, basically, and then next we move to the skeletal formula. When you guys get to organic, you'll also hear being called by different names. We can hear that it's called by a new name, which is called the Cuckoo Lee, or Cake. You'll structure So K E K U l e. With a little, uh, accent mark above the so called Coulier or cake You'll, depending on which professor you get because they pronounced him differently. Um, that's a structural formula. Skeletal formula. Now, how do we read something like this? What you need to realize here is that every end is a carbon every end and every corner is a carbon. So there's a carbon here, here, here, here and here. So at both ends there's a carbon, and basically at every edge there's a carbon. Now the rule about skeletal formula is that you cannot show carbons. Carbons are invisible, they're there, and we just can't draw them. And also, any hydrogen is connected to them are also invisible, so the carbons are invisible and the hydrogen is connected to them are invisible. Now, if you have an O. H or N H or some other group, if you have a different element than carbon and it has a cheese on it, then you'd have to show that different element, and you can show the hydrogen is connected to that different element. So again, when it comes to our skeletal formula, carbons are invisible and the hydrogen is connected to them are also invisible. The Onley way I could show those hydrogen is that those hydrogen were connected to something different from carbon, such as a halogen, such a sulfur or phosphorus or oxygen or nitrogen. Now, remember, we said that carbon is tetro Valent, meaning it needs to make four bonds to be satisfied. So every end, every corner is a carbon. So what you need to realize here is that if this is a carbon, we see it making one bond with another carbon. So that must mean it has three hydrogen is on it that we don't see. Why does it need three hydrogen? Because again, carbon is tetra valid. It needs to make four bonds, then hear this. Carbon is, um we see it making one bond to bonds. So that means it has to hydrogen is we don't see toe. Help it get to four. Bonds totaled. Same thing with this carbon. We see it's connected toe 12 carbons, so it must have to hydrogen is we don't see in order to get to four here, this carbons making one to bond. So it needs to more hydrogen to get to four. And then finally the end carbon. We see him making one bond here, so I must have three hydrogen. We don't see now. You're also hear about your professor talking about the ball and stick way of drawing these. That's with, like, models and stuff like that. But when it comes to actually taking the exam and doing the work, um, either online or in class. These are the three predominant formulas that we use for any organic molecule we can draw as a structural formula where we expand all the bonds out. We can draw it as a condensed formula where we push the bonds in, or we can draw it as a skeletal formula. What we do not show any carbons or the hydrogen is connected to them. Now that we've seen this, I want you guys to attempt to do some of these example questions. We'll come back, take a look at each 11 by one and see what's the best way to look at. Remember every corner, every edge is a carbon. So I hope you guys a little bit on this first one. So every end, every edge is a carbon. So all those that have marked our carbons and remember carbon is Tetra Valent. So what does Tetra Valent mean? Use that to determine the number of hydrogen on each of those carbons. Once you figure out the total number of elements, then you can get the molecular formula also remember here, Why do I have to show this hydrogen now? Because it's connected to an element different from carbon. It's connected to an oxygen. So now we can show it. This oxygen up here is different from carbon. It has no hydrogen on it. We know that hydrogen is not gonna be invisible on it because again, if it's an element different from carbon, we can show the hydrogen is connected to it. So guys, try to attempt to do this question on your own will come back and take a look at this first one here.