in this video i'm going to give you a basic introduction into drawing simple lewis structures so the first thing you need to be able to do is determine the number of valence electrons in an atom hydrogen has one valence electron so when you draw the structure of hydrogen it looks like this beryllium which is in group two has two valence electrons so this is the lewis dot structure for beryllium carbon which is found in group four has four valence electrons and so when you draw a lewis structure you only show the valence electrons nitrogen has five oxygen has six valence electrons and fluorine has seven so first you want to space out the electrons evenly before you pair them up so oxygen which has six you can draw like this if you want and then fluorine has seven so that's how you can draw simple lewis structures of the elements now what about when these atoms combine and four molecules what can we do so let's say for example if we want to draw hydrogen gas so each hydrogen atom contains a single valence electron and hydrogen likes to form one single bond so these two electrons will get together and form a single bond so this is going to look like this a single bond represents two electrons so now let's look at another example what about chlorine gas chlorine is a halogen which contains seven valence electrons so if we draw the separated chlorine molecules or atoms it's going to look like this now the halogens like fluorine chlorine bromine they form they like to form only one bond and so these two electrons will be used to generate the single bond of the chlorine molecule so this is how you draw the lewis structure of cl2 so as you can see these two electrons were used to form the covalent bond within the chlorine molecule now it's very helpful to know the number of bonds certain elements like to form for instance carbon has 4 valence electrons and in order to get 8 it likes to form four bonds it forms a bond to acquire a new electron nitrogen has five valence electrons and in order to satisfy the octet rule it needs three more electrons to get to eight so nitrogen likes to form three bonds to acquire those three electrons oxygen has six valence electrons it needs two more to get to eight and fluorine has seven valence electrons and only needs one more to get to eight so fluorine likes to form a single bond oxygen likes to form double bonds now to the left of carbon you have elements like boron boron doesn't follow this nice trend in fact boron doesn't want to gain five electrons in order to satisfy its octet requirements rather it prefers to give away its three valence electrons so boron likes to form two bonds beryllium prefers to give away its two valence electrons so beryllium likes to form two bonds so elements on the right side of the periodic table like carbon and everything to the right of that they like to acquire electrons so therefore you'll see that these numbers they add up to eight elements to the left of carbon like beryllium and boron they like to give up their electrons so the number of valence electrons tend to correspond to the number of bonds that they have or that they like to form so that's the general trend that you see as you continue to draw lewis structures in the future so let's draw the lewis structure of oxygen gas so each oxygen atom contains six valence electrons but i'm going to draw like this by the way when i draw an arrow a full arrow represents the flow of two electrons a half arrow represents the flow of one electron now we know that oxygen wants to form a double bond so each bond represents two electrons so therefore we need four electrons these four electrons will be used to create this double bond and so oxygen has four electrons left over that didn't participate in a reaction and on the right side we also have four electrons so this is the lewis structure of the oxygen molecule now how can we draw the lewis structure of methane using the same technique carbon has four valence electrons and every hydrogen atom contains one valence electron so when these elements get together to form methane you can see that this is going to represent one single bond this is another and that's another single bond and here's another so methane looks like this this is the lewis structure for ch4 so let's consider our next example ammonia how can we draw the lewis structure of ammonia now nitrogen has five valence electrons and hydrogen each contain one valence electron so these two electrons will be used to form a single bond that's another single bond and that's going to be another single bond so the lewis structure for nh3 looks like this as you can see nitrogen likes to form three bonds as you mentioned before and hydrogen likes to form one and in the last example we see that carbon has the four bonds that it likes to form so now let's try another example let's try the lewis structure of water now oxygen has six valence electrons which i'm going to place like this and each hydrogen atom only has one so these two will be used to form a single bond and those two electrons will form a single bond so you can draw the lewis structure like this but water does have a bench shape so if you draw it with the appropriate geometry technically it should look like this so that's the lewis structure for water it has a bent shape now let's try another example let's try oxygen difluoride how can we draw the lewis structure for that so oxygen has six valence electrons and fluorine has seven now we know that fluorine likes to form a single bond and oxygen likes to form two bonds so this is going to be one bond and there's the other so the lewis structure looks like this so that's the lewis structure of of2 oxygen difluoride but keep in mind in reality it has a bent shape just like water now let's try a harder problem draw the lewis structure for hydrazine and two h2 now keep in mind hydrogen likes to form one bond and nitrogen likes to form three bonds so because nitrogen likes to form more bonds than hydrogen we're going to put in the middle so every nitrogen atom has five electrons or valence electrons and the hydrogen atoms only contain one so we need to form three bonds with each or for each nitrogen atom so we can say this is going to be one bond this is going to be the second bond here that's the third bond that's for the first nitrogen these two could form a bond and those two could form a bond so right now we have a structure that looks like this and as we can see that each nitrogen atom has two electrons left over which we can draw as a lone pair so that's the lewis structure of hydrazine n2h4 now let's try acetylene c2h2 so we have two carbon atoms and two hydrogen atoms so every carbon atom has four valence electrons and hydrogen only has one now keep in mind carbon likes to form four bonds and hydrogen can only form one bond so this is the only bond that hydrogen can form so we can draw that as ch and we could put a single bond between the two carbon atoms we could also make another bond here that's a double bond or we can make a triple bond if we make a triple bond each carbon atom will have four bonds and so it turns out that this is the best lewis structure for the acetylene molecule c2h2 you