in this video we're going to be looking at a concept called leis structures and how to draw calent compounds this is a topic that you'll see in your chemical bonding unit in your high school chemistry class by the end of the video you should be able to identify single double and triple calent bonds and draw electron dot diagrams or Le structures for each so there are some basic steps for drawing Le structures the first thing you want to do if you're drawing a leis structure for a calent compound is to make sure that that compound is actually calent there are ionic compounds and metallic compounds out there for it to be calent it must be atoms that are non-metals non-metals bonded to non-metals in an earlier unit the periodic table unit you should have learned that the non-metals are situated on the right hand side of the periodic table from groups 13 over to group 18 so just check to make sure that you don't have a metal in your compound so step one is to count all the veence electrons step two determine the central atom step three draw single bonds to the central atom step four put all the remaining atoms as lone pairs on Terminal atoms then turn lone pairs into double or triple bonds if needed to ensure that atoms have an octet or eight veence electrons around them remember in chemical bonding elements want to have eight veence electrons to be stable unless you're hydrogen or helium then you want to only have two veence electrons so let's let's do a simple let's do a common compound that uh we're used to so let's do um yeah let's do do H2O do water okay so the first step is to count all veence electrons so what I would do is I would just set the elements up on the side here I would I would get my total count total veence electrons Okay so hydrogen has one veence electron it's in group one of the periodic table and there's two hydrogen atoms so I multiply by two so those two hydrogen will bring two electrons oxygen has six veence electrons oxygen is in group 6A or group 16 and elements that are in group 16 have six veence electrons we'll do another video about how to identify veence electrons um but the easy way is to use the periodic table and look at the group number so the last digit of the group number is the veence electrons except for groups 3 through 12 um those are a little bit more tricky so there's one oxygen atom so 6 * one oxygen atom is six then if we add these up you get eight total electrons sorry eight total veence electrons and what are valence electrons veence electrons are the electrons that are in the outer um the outer part of the atom there's electrons that are closer to the nucleus and there's electrons that are farthest so the veence electrons are let's do it here veence electrons they are the electrons farthest from the nucleus they're in the highest energy level like I said we'll do another video on if I haven't already on a electron configuration and uh how to determine who are the electrons on the outermost farthest I'll do outermost outermost ring outermost energy level and so there's eight total that come to this bonding Arena and so we're going to create this water molecule so the second thing you do is we did one um determine the central atom so the central atom will be the atom that can make the most bonds often time it's carbon who can make four bonds or any element in group 14 in this case oxygen likes to make two bonds it's in group 16 or group 6A so it's two away from the noble gases in group 18 or group 8A so it'll make two bonds it likes to hydrogen only likes to make one Bond so oxygen makes the most Bond so it'll be Central and then the other way you can figure out who Central is whoever the least electr negative atom is that would be the one that's farther left and down the table so we'll draw this so determine Central atom it's going to be oxygen here put oxygen in the center and then we'll draw single bonds to the central atom so a single Bond is um let me do a different color here so this would be a single Bond and a single Bond one line is um two electrons two shared electrons okay so then that means a a um two two lines together would be four electrons and [Music] then three lines that would be six electrons these are shared electrons so we call them the single bond this is the single then you got the double and then you have the triple bond so one line single Bond two bold lines double bond three triple so we start by drawing single bonds to the centrom which we did and then we're going to to connect the um the two hydrogens to that so what we're showing here is that there's two electrons if I wanted to I could just do two dots like that but instead of doing that we we draw a line to show that they're being shared between the two atoms and then put all the remaining atoms as lone pairs on the terminal atoms so what's terminal do this do this draw single bonds and then the terminal atoms are the ones on the outside so I like to put them on first so we'll do what do we have what's our count here so there's two electrons here two in this Bond that's four right we have eight total so 8 minus 4 we have four left so we're going to put a pair here and then a loone pair here I like to space them out I don't want the two the pairs to be next to each other because um these are electrons and they have a minus charge and if you have two negative charges they repel each other so you don't want them to be close this is also why you probably have noticed here that um that I have the the bond the single bond is like farther down um it's it's like bent so I didn't I didn't put like you know the the oxygen like this you know them straight out because I didn't want these electrons these right this right here to be too close to each other so I I I put them a little as far as possible apart so that's what that would be the leis structure for a water molecule H2O and so when you look at this it says after you put all the remaining atoms as lone pairs turn lone pairs into double or triple bonds if needed to ensure that all atoms have an octed or eight veence electrons um except hydrogen um and helium doesn't is a noble gas so it doesn't really want to bond with anybody except hydrogen needs two um the reason why is it's electron configuration it can only uh have two electrons in its first energy level so if we look at hydrogen it's got two electrons it's got the two from this uh Bond right here it's sharing it so that counts as two and then the other hydrogen's got two that shared pair of electrons and then if you look at oxygen this this is interesting [Music] um because a lot of students when they're first doing this the shared electrons so let's do let's do this so this is a shared pair that's bad it's not good let's do shared so that's a shared pair and then this pair here is called a lone pair right so loone Pairs and shared pairs both count so if you if you look at oxygen it's got one it's got um let's do let me do it in green just so you can see it it's got one two three four remember this is a shared pair five 6 78 so the o oxgen has eight electrons around it it's just that these are single bonds right here these are actual single bonds shared electrons it's getting messy now but they're shared electrons whereas it has two pairs of Lone two lone Pairs and two shared pairs but it's got two four I count we want to count in twos from here and out 2 4 6 eight and everybody needs to have eight veence electrons around them to be stable so this would be the correct leis structure for water all right so the next one we'll do is cf4 so it's the name of this is um when you're naming coent compounds that could be another lesson but it's a carbon and then f is Florine but it turns into floor ey and there's four Florine so it's Tetra Tetra fluoride so we'll draw this compound and so start out with our count right so got carbon and we got Florine so carbon has four veence electrons there's only one we just do electrons do VE for veence electrons here there's only one carbon atom so that's four and then Florine there are seven veence electrons for every Florine atom times four Florine atoms which is 28 and that'll give us 32 total 32 total veence not total electrons in the atoms but veence the ones that are involved in bonding so let's let's draw a structure then so we'll put the central atom is going to be the atom that makes the most bonds uh carbon likes to make four bonds and Florine likes to make one Bond because Florine is one away from the noble gases carbon's four away so it likes to make four bonds so we're going to put carbon in the center and then once we do that we're going to connect the um other atoms the terminal atoms around the central atom with single bonds so do there Florine there the reason why I'm keeping uh the Florin kind of spaced out is because the electrons they repel each other so they don't like to be near each other so I got my count so it's 2 4 6 8 there's eight electrons here right now because each single Bond counts as two electrons so 32 minus 8 what do I have left 24 right so I'm going to go put these lone pairs around this terminal atoms 2 4 6 8 10 12 14 16 18 20 22 24 you'll notice I'm putting six around because there's already a single Bond right here so that's that's gives me eight and I don't what I don't want to do is I don't want to put electrons I don't want to put electrons near the uh bonds because in the bonds are electrons as well so I don't want to do that okay so then I and I check my uh see if everybody has octat so this this Florine on the left has 2 4 68 the Florine up top has 2 4 68 the Florine around on the right side has 2 4 68 around it and the Florine on the bottom has 2 four 6 8 remember when I count these 2 4 six eight so this is a single Bond and in a single bond is two shared electrons all right let's do another one oh well before we do that the carbon we check the carbon the carbon has two this is two carbon two 4 six and then this other green one at the bottom is eight so the carbon has eight veence the flines have eight and if I do my total count there's 32 electrons in this molecule and so that gets me my 32 that I had to have all right in this one we'll do do pf3 so this one is um phosphorus and then three flines so Tri Tri fluoride that's you got to do in chemistry you got to try that's why it's called chemist try right all right let's do our count here so phosphorus Florine each phosphorus how many electrons does each phosphorus have phosphorus is in group 15 of the periodic table so it's got five veence electrons and there's only one phosphorus so there's five from the phosphorus and then Florine seven veence electrons it's in group 7 a 17 times three of them three flines so it's 21 so I got to have 26 total here all right let's do this so I'm going to go ahead here in central atom so Florine likes to make one Bond because it's one away from the noble gases and then phosphorus likes to make it's in group 15 three away from group 18 so it likes to make three bonds so we're going to put phosphorus in the middle because it makes the most bonds and then we're going to connect the um we're going to connect the phosphorus to the three Florine so we'll go let's go um we'll do white I guess so one two three we'll go Florine Florine Florine so there's our three atoms and then once we have that then we're going to so that's two when we kind of make this count here right Let's do let's make our count so we used two here four I'm trying my best here not to make two lines but two 4 6 so 26 - 6 that's 20 left so we'll add the 20 as lone pairs around the terminal atoms so 2 4 6 8 10 12 4 14 16 18 so that's that's 18 now right 20us 18 we have two left so then we're going to go up here and we're going to put the the extra loone pair on the central atom at that point you can right I just like to put it around the outside first and then if I have room I can put it around the central last and then what I want to do is I want to check my octat roll here this Florine outside here so let's let's come after this in a different color ready let's count them two 4 6 eight so that florine's good let's look at this Florine two 4 six eight that florine's good let's look at this Florine you can see it's the same right two 4 six eight and then look at this phosphorus the three green single bonds 2 4 six eight so everyone has the octet everyone has eight veence electrons around it and if you look at our final count we'll count them 2 4 6 8 10 12 14 16 18 19 20 22 24 26 there's 26 electrons in this molecule and we said we needed 26 total and we have it so we don't need any double or triple bonds here so we're done all right let's do another one here so we'll do let's do s O2 we'll do sulfur I do that white if I was doing in white sulfur dioxide because die for two oxygens so we'll do my count here sulfur and oxygen sulfur and oxygen are both in group 16 of the periodic table so they both have six veence electrons there's only one oxygen here here sorry there's two oxygen here that's 12 total electrons there's only one sulfur remember this is our veence electrons this is our number of atoms and our total here is 18 total very important you can't have any more or less than 18 to build this Sol every suver dioxide molecule has to have 18 B electrons so let's set it up so in this case both of them like to make the same number of bonds but the way you break this tie is there's one less sulfur than oxygen so there whoever's the least amount of the atoms will be Central or the one that's the least electr negative which is sulfur so sulfur is going to be in the center here and then we'll put oxygen to the right oxygen to the left keep them far apart and then we'll connect them with single bonds so go one two they connect them that's two four electrons 18 - 4 that's 14 left so then we'll go 2 4 6 8 10 12 2 4 6 8 10 12 14 16 total so we have two left so then we'll go two right there okay this is important if you if you count these again if you recount these 2 4 6 8 10 12 14 16 18 so we can't add any more electrons and we can't take any away we have to make the bonds and the molecule stable and and correctly bonded with the electrons we have so if we count this left oxygen it's got two four six eight so it's good although it likes to make two bonds this oxygen on the right is two 4 six and eight so it's good with the octet so there's eight eight here and eight here on the oxygen look at the sulfur two for this Bond four six so the sulfur in the center doesn't have eight bance electrons around it so we have to we have to make that happen it has to have um eight now if we bring this pair this is where we have to like make doubles or triples if we bring this pair in to make a bond right here and then we want to eras that because we just moved it so we don't have extra now let me erase this so it looks better so that I have a double bond here so I just made a double so if I count this this Central sulfur has 2 4 six it still has six and now this oxygen out here has 2 4 6 8 10 which makes it breaks the octet rule so that has too many so we have to put that pair back so what you want to do at this point is we want to move a pair from the oxygen in to make a double bond and then We'll erase that so that we don't have an extra pair that we just created from nowhere so now if we count it right let's count it so we have two 4 6 8 so Oxygen's good now let's look at a sulfur two four 68 so the Su for now has eight so we're good and this oxygen over here is two 4 6 and eight so this this Oxygen's good and I know this isn't way we want it you're like oh can we really have a double and a single Bond or do we have to have all singles all doubles all triples in this case you can have a single bond to the one sulfur and a double bond to the other because that's what satis satisfies the octet rule so this one's a little different than what we've drawn in the past but um this is how you would draw sulfur dioxide all right let's do this last one this one is carbon dioxide okay so it's what you're breathing out at me or at your computer screen while you're watching this if you got this far die for two oxygens so let's make our count so carbon is in group 14 it's got four veence electrons there's only one carbon this is the number of atoms this our veence electrons VE for veence and so we got four there and then oxygen is group 16 so it's got six veence but there's two oxygens so 6 * 2 is 12 this one has 16 total 16 total electrons in this one so carbon's going to make the most bonds it's in group 14 I likes to make four bonds and oxygen likes to make two bonds because it's in group 16 or group 6A so we'll put carbon in the center and then we're going to go ahead and connect the oxygen to oops I don't want to do that we'll go ahead and connect the uh oxygen to the carbon put another oxygen on here so we have four right there right so 16 - 4 is equal to 12 left and then we're going to add the the rest as lone pairs around the terminal atoms so two four 6 8 10 12 so we used all 12 or all 16 total now 2 4 6 8 10 12 14 16 electrons the oxygen is good it's got 2 468 around it the other oxygen on the right side is good it's got 2 468 around it so when you look at this so here's two here's four six and then it's got eight and then this oxygen two 4 six and eight with this single Bond so that's eight there okay now um let me get that a little bit better so the carbon you can see only has a single bond to the left two and a single bond to the right four so it's two four but carbon needs eight around it and we can't add any more electrons because we already have our uh 16 total so we can't add electrons and we can't take electrons away so we got to make carbon stable or happy with the electrons that are there so we're going to move into our final step to make doubles and singles so we'll make a double bond here and we'll make a double bond right here by moving in electrons and then we're going to go ahead and erase those that we just moved and if you recount this now now oxygen has it's 8 2 468 carbon has 2 468 and oxygen is 2 468 so we're stable and uh this would be the correct Lew structure for carbon dioxide well I hope you enjoyed the video and I hope that you've learned to draw calent compounds also known as leis structures and that you can identify a single double and a triple bond just remember to follow those steps don't do your single don't do your double and your triple bonds till the very end and make sure you always have a a good handle on the count of total electrons when you're doing them if you have any questions or you'd like me to do any other structures in the in the later video uh just please leave it in the comments uh also if you have any questions