on the previous lecture we went ahead and learned about the skeletal structure and our goal is twofold the first is if we have a loose diagram we want to be able to convert it to a skeletal structure and if we have a skeletal structure we want to insert back those invisible hydrogens and turn it back into those diagram so let's do an example in this case we have a ketone of sort and converted that into a skeletal structure and what do we do well the first thing i suggest is to highlight the longest carbon chain in this case the longest carbon chain is going to be six right so i'm going to draw that first one two three four five six and then i'm going to start adding feature from the first carbon all the way to the end so the first carbon here have an o h and therefore i'm going to put an o h here and the next carbon have a double bonded oxygen so i'm going to put double bonded oxygen there the next one the o h is there right then another oh sticking upward and the other one here is sticking upward but you know in skeletal structure it doesn't matter because it's tetrahedral it's not a square so we put it there and the last one here the last carbon also have an o h so i'm going to put it down here all right so that's going to be the skeletal structure of the materials that we have here and again one of the rules that we're going to use whenever we have a skeletal structure is we're not going to draw the hydrogens that is attached to carbon so that's why those hydrogens are not visible in the picture that we have yet now of course since the hydrogens are invisible you know our task is that we also need to know how to put them back in so in this case if we have a molecule that looks like this what would it look like if this were a a lewis diagram and we should insert the car the hydrogens as well now before i go on to draw the lewis diagram just kind of remember if you want to insert back the invisible hydrogens remember that carbons have four bonds and if you see that they're missing that means there's going to be a hydrogen on there as well so if you look at these carbons or actually any of the carbon that is represented in the molecule bends in here that there's only one two and three bonds attached to it so that means is that there's going to be one more hydrogen sticking out the same with all of these so that means each of these carbon have a hydrogen on it right so what it means is that the actual lewis diagram of this material is going to look like you have the hexagon with all carbons and then you have one hydrogen each attached to the carbon and now that's going to be the lewis diagram of the molecule benzene right here and let me eliminate the uh the hydrogens that i just donated there right and part of the reason why we're using the skeletal structure inside of the lewis diagram is that you know as you can see that drawing the benzene molecule is a lot faster in the skeletal structure compared to the lewis diagram that we did here and on next portion of the clasp we're going to start to learn how to name these materials