Determine whether each molecule is polar or nonpolar. b. SiCl4

Video transcript

Hey everyone today, we're being asked to identify which of these four molecules is the polar one. Now the easiest way to do this would be by drawing out the LewiS structure for each molecule And then identifying which one has a diaper moment that causes it to be polar. Before that however, I'd like to point out that we can actually eliminate one of our answer choices right from the get go and this will be and the choice c now recall that on our periodic table electro negativity increases from the bottom left to the top right of the periodic table, excluding the religions of course. Or sorry, excluding the noble gasses. So carbon is further to the right than hydrogen And in Ch four methane there's only one bond or one type of bond, I should say the carbon hydrogen bond. Now, even though carbon is more electro negative, the difference in their electro negativity is is still small enough that we consider this to be a non polar bond. It's a non polar bond. That's why that here bond. So therefore, since methane only contains these non polar ch bonds, methane itself is a non polar molecule. So we don't have to go any further than that. For the rest of them though, let's go ahead and start drawing out our LewiS structures. Let's take a look at a xenon d fluoride. So the first step to drawing out of lewiS structure is identifying how many valence electrons are present within the structure. Xenon is one of the noble gasses. So it has eight valence electrons. It's in group eight on the periodic table Florian is one of the allergens in group seven and will have seven valence electrons and we have two of those. That brings us to 14 plus 8, 22 valence electrons in xenon fluoride with that in mind. We can go ahead and start drawing out our structure. So Zenon will be our least electro negative atom here since it is a noble gas. It doesn't really attract electrons to it. It's inert Susan and and being in the center and it will be attached to either flooring on either side. We can fill the updates of each flooring like so And in our molecule right now, that means we have 8:16 valence electrons. We're still missing six however, but we can add those onto the central atom since the octet of the rest are filled. No. On a side note you may be wondering why Xenon Has 10 atoms around it. It has more than eight electrons and has more than an octet. Well, this is because xenon, like other molecules such as phosphorus are elements that can have an expanded octet. They can actually hold more than eight electrons in their outermost shell with that in mind. However, due to the repulsion forces experienced by these lone pairs, this causes the molecule to be linear. It is it'll be straight which means that these xenon flooring bonds which are extremely polar towards the florins. We'll have a diaper moment there because flooring is far more electro negative than xenon. Even though these are polar bonds, the diet poles cancel each other out, meaning that zenon de fluoride is non polar. It's non polar. This can slide out. Let's take a look at B ammonia. So, nitrogen is a group five element has five valence electrons. And hydrogen is in group one has one valence electron and we have three of those, Which brings us to eight valence electrons drawing that out. Since the only molecules are nitrogen and hydrogen and hydrogen can never be essential atom except when bonded with itself, nitrogen will be our central atom. We can bonded to three hydrogen giving us six valence electrons present in the single bonds, meaning the last two can be added as a lone pair on the nitrogen because of this lone pair on the night on the central nitrogen, it actually forces the rest of these bonds downwards and causes it to have a sort of tribunal pyramidal shape like a triangle pyramid sort of like that. No nitrogen is further to the right then, carbon is on the periodic table. It is one group over as such. It is more electro negative than carbon and it will actually form polar bonds with the hydrogen. Unlike carbon, which means each bond will have a die pool moment facing the high nitrogen, which in turn means that we'll have a huge net die po facing up since we have an unequal die pool here. This means that NH three or Ammonia is a polar molecule. So we have our answer. But just to be careful, let's go back and finish out the lewis structure. For boron dry fluoride. That Boron is a group three element has three valence electrons. And like we mentioned earlier, Florian is in group seven. It's a halogen. So will have seven valence electrons have three of those. 21 plus four or sorry, 21 plus three gives us 24 valence electrons. Let's go ahead and dry that out. Boron is least election negative. So it goes in the center attached to the florins. We fill their act it's 123, 123. So this will give us 8 16, 24 valence electrons. So we have our final lewis structure. Now florian is the most electro negative element on the periodic table. And it's further to the right than boron. So each boron flooring bond will be pulling however, since the bonds all facing opposite directions and we have a symmetrical molecule, the disciples cancel out which means boron trap fluoride is non polar. This means we've isolated b ammonia as our answer. So the only polar molecule here is ammonia. I hope this helps. And I look forward to seeing you on the next one