okay folks in order to distinguish families that arise from function groups you must begin seeing like an oenus what does that actually mean it just means you must know how to First recognize and then draw carbon skeleton so carbon skeleton is going to be probably the way that you're going to see most of our compounds in organic chemistry because it allows us to keep all the information about the actual organic compound without having to write so much okay so you'll see the skeletal structur that just show carbon atom and carbon carbon bonds as line okay and of course if it's attached to any other atom or any kind of functional group you'll see their attachments of wood what attachments you won't see are the carbon hydrogen at okay folks so it's all about making sure you recognize things so sometimes that also includes recognizing the L structure and the convinced structure let's start with the MCT form here we have c3h8 that means we have three carbons and h8 so we're taking lectum formula and we're using leis Theory just like in 101 and creating a Lu structure but because we have multiple carbons and they're all the same electro negativity we need to make sure that all going to go on the middle so for the L structure we have three carbons in the middle of fing and then we have it flush with all the hydrogen again you can call this the hydrocarbon because it's only carbon and hydrogen few so again you want to just remember from one one the least electronegative is in the middle and if there's multiples like we see here they all so the L structure sometimes called the complete structure sometimes called the expanded structure is going to give you all bonds that you see attached to carbon all of them okay and so yes that could be great but think about it if you had a carbon that's like 12 if you had a structure a granite compound that's like 12 carbons for example you're going to be drawing a lot and so the L structure is not going to be your best friend when it comes to that so when I again into chemistry we go a little bit further we say Okay instead of having L structure let's go ahead and create our condensed structure it's better because again it reduces the amount of drawing by eliminating um the lines between carbon and hydrogen sometimes you will see condensed structures look like this okay and that's just showing you that this bond is showing the bond between carbon and carbon so yes can this structure can either take all of the lines away like you see here all the bonds to carbon or it can show carbon carbon bonds okay folks so just keep that in mind another thing about the condensed structure that you will see is that sometimes it also shows repeated units so say we had more carbon it wasn't just C3 here and we have more carbon you can put actually ch3 and then in parentheses all right say you have like five ch2s you can put ch2 there so technically we have five six seven carbons in this structure but if you have repeated units instead of writing ch2 ch2 ch2 for the condensed structure you can simply put in parentheses and have a superscript of the amount of those repeated portions okay again carbon is modular modular so it can have all these little pieces coming together which is pretty cool all right you also can see the condensed structure that includes like say um carbon attachments to heteroatom like nitrogen oxygen Etc we'll see that as well so condensed structure can show you a lot and no matter what you should be able to go between the condensed structure to Le structure and conen structure to a skeletal structure now skeletal structure is a bigon what we like to see it's easier to draw it's all going to be lines based on those carbon carbon bonds okay now skeletal structure it simplifies everything but if we have something like an oxygen group attached here or nitrogen group we definitely write out the actual functional groups or hetero atoms for it okay hydrogen are not drawn and then you see carbons is represented at the end points of the line so let me just erase this here and show you this will be a carbon atom this will be a carbon atom this will be a carbon atom I kind of just wrote little mini carbon mans just to show you that hey these are carbon atoms you don't show the connection between the hydrogens here because again that is going to be excess writing that we mainly see in the L structure also we are assuming that each carbon has an octet that's another reason why we're like oh we don't need to look at the hydrogen atoms there because we know that carbon has an octet and so we just fill up however however many hydrogen atoms are needed if it makes a double bond or triple bond of course we fill up less hydrogen atoms that are needed now let's talk about lone pairs but with the skeletal structure sometimes when you have hetero atoms attached you actually will not see the lone pairs written if I have a nitrogen we know that nitrogen likes to make three bonds and have lone pair sometimes you'll see it written and sometimes um you won't okay so here I'm like I have a cell structure that's attached to the nitrogen so we know that we can write the long pairs or if it's not written you should already assume that you know that there's long pairs there because of how nitrogen exils okay same thing with oxygen you should assum Ox is going to have two long pair groups if it's making tubon but really the pairs of optional something that's not optional when you're talking about F construction definitely not optional is going to be formal charge so formal charge let's go ahead and rewrite that formal charge is going to equal to your V electrons minus lone pairs plus half of your bonding pairs or whatever way that you learned it okay so veence electrons minus lone pairs plus half of your bonding pairs so again if I have my nh2 here if I want to get the actual veence or formal charge of nitrogen I'll say okay five ve electrons minus long pairs is going to be two plus one half of what is bonding to so that's going to be 1 12 of three okay and of course um not one half three one half of six sorry half of six because each bond is going to represent the sharing of two electrons right so this is going to be 5 - 2 + 3 which is going to be 5 - 5 which equals zero so the formal charge here is zero that's why it's like you don't have to write it but anytime you have a charge that's actually attached so let's go ahead and do this say you have an oxygen that has a minus charge you must keep the formal charge it's going to be attached with any hetero okay so just keep that in mind as far as let's give a couple more examples all right so let's just say we have this skel structure here and we're going to have oxygen no it's going to have NH3 but of course we don't have instead of Lone pairs we're going to make plusy now you have to ask yourself well can I get rid of that plus the answer will be no you have to make sure you can recognize these car spell from all these different forms and be able to go back and forth between them but also stop yourself and say wait a minute do I need to have lone pairs here you don't have to unless the question specifically saided for example do I need to have a charge yes so let's go ahead and get the uh charge of this nitrogen here so again we have 5 electrons Min lone pairs don't have any plus 12 of8 okay so 5 - 4al to plus one that's how we got the plus one charge here that see those charges go ahead and keep all right we also know that we're looking at another flash card moment folks so on the front of a flash card you can write carbon skeletons on the back you can write some examples of L structures condensed and skeletal structure let's go through a a couple of examples just to get it started