Some of this video, we're gonna go over question 128 from chapter eight, which asks us to write Lewis structures and predict whether each of the following is polar or non polar. So when a were given a Josie and and we were told that it exists is h o bonded to CNN. Um, so we know that our hydrogen will bring one valence electron. Our oxygen atom will bring six valence electrons, and our carbon will bring four valence electrons, and our nitrogen will bring five. So that all tellings together to 16 electrons that we have in order to draw this Louis structure. Um, so we know that we'll have hydrogen and oxygen bonded to carbon and nitrogen. Um, and we know we can go ahead and fill in the octet on oxygen. Uh, and we know that carbon, who normally has four valence electrons, likes to make four bonds. So rather than just having my carbon and nitrogen simply bonded to each other, I'm going to triple bond. Hm. And this uses up 2468 10 12 14 of my electrons. And I have two electrons remaining, so I'm gonna put my last loan pair of electrons on the nitrogen atom. Now let's assess this on Louis structure based on formal charges. So the formal charge in hydrogen the zero, um, remember formal charges equal to the number of valence electrons. The Adam usually has minus the number of electrons and lone pairs around that Adam, minus half the number of electrons in the bonds that that Adam is making. So for oxygen. Here we have six minus four minus two. That's a formal charge of zero for carbon. We have four minus four. That's a formal charge of zero. And for nitrogen we have five minus two minus three. So that's also a formal charge of zero. So having formal charges of zero means this is a good Louis structure. So now we want to use that to predict whether or not this molecule is polar or non polar. So we do have these polar bonds between carbon and nitrogen and even more so between carbon and oxygen, because oxygen is much more Electra negative than carbon on. Because of that, this was a polar molecule, um, sometimes and we have polar bonds, but they're placed symmetrically with a Knick with violent bond countering it, um, we end up with a non polar molecule, despite the polar bonds. But in this case are polar bonds are not placed symmetrically, So we have a polar molecule. So, Inbee, we have C o S s O. I know that my carbon brings bore valence electrons both oxygen and Solberg will bring six Valence Electron, so I'd have a total of 16 electrons to work with. Um, when I'm thinking about which Adam, I want to make my Central Adam. Usually the best choice is the least, Electra. Negative, Adam. So in this case, I'm gonna use carbon. Okay, Um, so I know that if I were to just fill in the octet on my oxygen atom, that would give me a formal charge of minus one on oxygen because we would have six minus six minus one. But if instead of, um instead of having a single bond and filling in my octet, I have a double barn, and then I feel in my October than my formal charge is six minus four minus two. Um, and because sulfur has the same valin, see, it's favorable to do the same thing to sulfur since we'll have six minus four minus two equals zero. We have a formal charge of zero on both oxygen and sulfur now, and we've used of all 16 of our electrons and more formal charge on carbon is four minus four. So that zero as well s. So we have this linear molecule, Um, and we have these two bonds. We know that oxygen is more electra negative than carbon and sulphur is more Electra negative than carbon. But our oxygen carbon bond is more polar than our carbon sulfur bond s o. This bond is more polar than this bond. And so the overall molecule is polar. And see, we have co two eso where carbon brings more electrons, and then both of our oxygen atoms bring six valence electrons. So we have a total of 16 electrons to work with, since carbon is the least selector negative, Adam, I'm gonna make it my central adam, Um, And again, I'm bonding to two oxygen atoms. And I know that if I were to have a single bond oxygen and fill in my ock tight, I would have a formal charge of minus one. But rather than doing that We're going to do a double bond and fill in the OC type, which gives us a formal charge of zero, and then we can do the same thing to our other oxygen atom. Formal charges. Zero on guy uses up all 16 of our electrons and then the formal charge in our carbon atom is four minus four is zero. So we pretty much have the same structure as C E O s 02 Um, but C E O. S was polar because of the different CEO and CS bonds. I'm here. We have two CEO Bonds s Oh, they're equally polar, and they're pointing in opposite directions because this is a linear molecule. Um, so this is a non polar molecule because of the symmetric placement of the polar bonds. Indy, we have CF to seal, too. So we're carbon out and brings four valence electrons. Each of our florins and Corning's bring seven valence electrons, and we have a total of 32 electrons to draw a Louis structure with. We're gonna go ahead and make carbon the central Adam because it's the least Electra negative. And then we barn are Florian's and are Koreans, so we can go ahead and fill in the octet. It's on each of our religions, which is going to use up eight times for electrons s O that will use up 32 electrons. So we've used up all of our electrons. Um and we want to know whether or not this structure is polar or non polar. So in order to do that, we need to know the molecular geometry. Not just look at the Louis structure, the last few molecules brewing here. But this one isn't. This one is what we call Tetrick, You troll. So we have a carbon atom, and then our religions are four corners of a tetrahedron, the bond pointing forward. And this is a bond pointing backwards. I So because we have, we have two different kinds of the halogen atoms are CF bonds are more polar than are sti C l bonds. Because Lauren is more Electra negative and chlorine, eh? So we have these different polarities and r c e f and R. C C l bonds. Um, so this molecule is polar and it'll have a DYP whole moment pointing towards towards the flooring Adams because those air more Electra negative in party, we have s e f six. So Cellini, um, bring six Valence electrons and then each of our floor ings bringing seven valence electrons. That's 42. So we have a total of 48 electrons to draw our Louis structure. So we make Cellini Amar Central Adam, and then we draw our 64 rings, bonded to it, and then we can go ahead and filling the OC texts on each of our flooring. Adams and we used up we used up six times a day. That's 48 electrons. So we used up all of our electrons. Eso Now we have a loose structure. What about the molecular structure for this? Um, well, we have six Adam's around one Adam. So the most stable way thio arrange that is as an octahedron. Um, so we have one foreign Adam above selenium and one below, and then in a square around Cellini, um, we have our other for flooring Adams. So each of our Cellini imploring bonds is polar because of the difference is an Electra negativity. But the fact that each of our bonds is countered by another bond pointing in the opposite direction means that this molecule is non polar. So because of the symmetry of the mollick of the molecular structure, our polar bonds still result in a non polar molecule. Finally, the last molecule we have is each to C o R formaldehyde eso. Each of our hydrogen atoms brings one valence, electron or carbon brings foreign oxygen. Bring six. So we have a total of 14 electrons to work with. Gonna go ahead and make the least elector. Negative, Adam are central Adams. We have carbon, hydrogen, hydrogen and oxygen. If I were to just fill in my octet on oxygen, I know I would have a formal charge of minus one, and that would also make my formal charge on carbon plus one, cause I'd have four minus three. So let's not do that. Instead, let's draw a double bond to oxygen and then fill in the oc tight. Now, the formal charge on oxygen is zero, and the formal charge on carbon is also zero. So that's a slightly better Louis structure. Um, So what's the molecular structure here? Well, we have, um it's gonna be tribunal plainer because we have three atoms around another Adam that has no electron pairs around. It s o. This is tribunal plainer. Um and is it polar or non polar? While our carbon oxygen bond is much more polar than our carbon hydrogen bonds, and we have only one of them are pointing in one direction. So we are gonna have a disciple moment in this direction, and it is gonna be a polar molecule.