A molecule with the formula AB3 has a trigonal pyramidal geometry. How many electron groups are on the central atom (A)?

Video transcript

Welcome back everyone to another video, a theoretical molecule with the formula XY three as a T shaped geometry. How many electron groups are on the central atom? A? And we're given for answer choices A five B three C two ND four. So let's solve this problem. First of all, let's understand that the given structure is xy three. That's the formula we have X as our central atom. And if we want to produce a T shaped geometry, we want to have our Y atoms above X below X forming a linear geometry. So far, right, we have a 180 degree angle and then we're going to introduce another Y on the right. Such a geometry is quite common. Let's suppose that we take a structure of chlorine bio fluoride which forms a T shaped geometry. This is a very good example. And what we want to understand is that this structure should be energetically favorable, right? The reason why it's energetically favorable is essentially because electronically it's supposed to form a trigonal pyramidal shape. So what we are missing in the given structure, those would be two loan pairs if we think about them right, meaning the electronic geometry would make perfect sense. We would have a trigonal bi Permal geometry. We can clearly see that meaning there should be two lone pairs on a to form an energetically stable structure based on the Bs Cpr theory. So now what we can sell is basically that a T shaped geometry should have five electron groups. And how do we know that? Well, we need to calculate the number of atoms bonded the central atom. A those are three atoms because we have those three bonds, right? We have 123 electron groups plus two long pairs, which gives us a total of five electron groups. And we can tell that the correct answer to this multiple choice question would correspond to the answer choice A five that will be it for today. And thank you for watching.