Classify each species as either a Lewis acid or a Lewis base. d. CN-

Video transcript

hey everyone. So here it says, determined whether the following is a lewis acid or lewis base. Remember lewis acid is an electron pair except er here, the species that commonly exists as lewis acids are species that are positively charged, then being positive would attract negative electrons. Also it can happen when the central element has less than eight electrons around it. It has room to accommodate a lone pair to reach the octet rule. Lewis base is an electron pair donor. This happens with negatively charged species. Or ones where the central element has a lone pair or compounds where we have pi bonds involved. So here if we look at ph two ch two, so carbon, remember carbon, it wants to make four bonds for to be able to do that. It would need to form a double bond with the phosphorus. Okay, so here doing that would help us to create a structure where the phosphorus now it's making four bonds would actually be positively charged. Now, another way we could draw this is we could have the lump. The pi bond here actually sit itself here as lone pairs on the phosphorus instead, which would make this carbon here positively charged since it has lost an electron in either case focused on the fact that we have either a pi bon involved or we have a lone pair involved. This first structure represents a lewis base. So this and this are out Now. BF three bonds in group three a. So it has three valence electrons. Since it only has three valence electrons. It can make three bonds collectively. Now it has six electrons around it, it has 246 electrons. It's not fulfilling the octet rule, so it has room to accept the lone pair, which makes it a lewis acid. Same thing can be said for aluminum chloride. Right? So here aluminum's in group three a. As well. So here aluminum As three valence electrons. That makes three bonds. And because of that it has room to accommodate a long pair to get closer to the octet rule. So this would also be a lewis acid and then finally we have the bromide ion. Remember if you're negatively charged, it means you have extra electrons at least one extra electron. Here bromide ion has all these lone pairs which you can use. It can donate them. So the bromide ion represents a lewis base. Based on this option, C would be our correct answer.