Lewis Dot Structures: Exceptions

some elements can have less than eight or mawr than eight octet. Electrons around themselves and maintain stability. Now recall their non octet number of electrons is two x their group number. So for incomplete octet, where they have less than eight octet electrons around them for group to A and B two times two, which is four for Group three A would be three times to, which is six so they can have Group two elements. Can have four electrons, octet, electrons and be stable. Group 38 can have six or just multiplying their group number by two. So five they could have 10 electrons and me. Okay, Group six. They could have 12, 14 and 16. So just remember, sometimes the octet rule is broken and it's still okay in terms of the lewis dot structure.

here. We have to draw the lewis dot structure for xenon di bromide molecule. So Zain on is in group eight A. It's a noble gas. So it has eight valence electrons, bro means a group seven. So it has seven, and there's two of them, so we have a 22 total valence electrons. Now, xenon will go in the center and here we're gonna be connected to our two bro means okay, Now, remember, your surrounding elements need to follow the octet rule. So we're gonna put our electrons around, bro Means so that they each have eight total valence electrons. Three lone pairs around them totalling six electrons. But remember, they're also sharing electrons from the single bond. So that's eight each one has. So that's using up 16 of my total 22 valence electrons. So we have six remaining here. The remaining six electrons. We have no choice but to put them around Zen on. So six electrons and we separate them evenly is lone pairs. And this would be the structure off xenon di bromide molecule. We can see here that Zen in has 2468 10 electrons around it. It's breaking the octet rule because it is an exception. Now it's non. It's ideal non octet number would have been 16, but again, that's when it's ideal here. We just don't have enough electrons to get to that number of 16. Instead, Xenon is okay with having 10 electrons around it. But here we're seeing that are central elements are breaking the octet rule, and it's still okay.

So some of you may have heard of the term free radicals. When discussing health and nutrition, we know that free radicals can damage healthy cells within our bodies. But what is a free radical look like? Well free radicals are just molecules or ions with an unpaid aired electron around an element In this case, we have this unpaid electron on the nitrogen atom. We're gonna say radicals, radicals or compounds Radical compounds always have an odd number off total valence electrons nitrogen in group five days. So it has five oxygen's group 68 so it has six. So this molecule has a total of 11 total valence electrons. Now, we're gonna say to draw to draw it, you place the electron on the element that gives least formal charges. So if we took the formal charge of nitrogen and oxygen, remember, formal charge equals group number minus the bonds. The element is making plus non bonding electrons. So nitrogen is in group five A. So it has five valence electrons. We see it making to bonds, and it has three electrons, so it equals zero. Oxygen is in Group six A. We see it making to bonds and it has four electrons that are not bonding, so it is also equal to zero. So both molecules have zero formal charges. Remember, we want to get all our Adams, if possible, within the lewis dot structure, as close to zero as possible. This gives us the best representation for particular molecule. Now again, the giveaway that we're dealing with the radical is when you calculate the total number of valence electrons and you get back in odd value, this is usually a strong indication that a radical maybe present, so play around and see what makes the most sense in terms of the free radical compound.

here, it says, Draw the lewis dot structure for the radical of nitrogen dioxide. So nitrogen dioxide is a very common example used to talk about radicals. If we look at the total number of violence, we have five from nitrogen, since it's a Group five a six times to oxygen's in Group six A. So it has six and there's two of them. So this has a total off 17 total valence electrons. It's an odd number of Valence electrons, so that's a strong indication we're dealing with a radical. We place nitrogen in the center. It forms single bonds to the oxygen's. Initially, make sure that your surrounding elements follow the octet role. Right now, we have a total of 16 electrons being depicted, leaving us with one electron left. The issue now is that nitrogen is not fulfilling the octet rule. It has 235 electrons around it. So remember when the element is not fulfilling the octet role. What we can do is make double or triple bonds. Here. We can't make a triple bond because then that would be too many electrons around nitrogen. It can only go up to eight for the octet role. So we're just gonna use one of the lone pairs on oxygen, either one to make a double bond. And in that way, nitrogen has seven electrons around it, and that's the best that we can do. This year depicts what the nitrogen dioxide molecule would look like. It is a radical because we have that one lone electron on top of nitrogen.