So here we're going to say that the electron geometry represents the simplest system for geometrical shapes that focuses on the number of electron groups around the central element. We're going to treat lone pairs and surrounding elements as the same. Alright. So we can have 2, 3, or 4 electron groups on the central element. So remember, when you have 2 electron groups on the central element, that's just 2 surrounding elements. When we have 3, then there are 2 possibilities. We could have here 3 surrounding elements or 2 surrounding elements and 1 lone pair. With 4 electron groups, there are multiple possibilities here, which is showing 2 possibilities, where it's 4 surrounding groups or 2 surrounding groups and 2 lone pairs. Remember, the one that I'm not showing that we talked about in earlier videos is you could have 3 surrounding elements and one lone pair as well, and that would still constitute a 4 electron group structure.

Now the number of electron groups determines the electron geometry. When you have 2 surrounding groups, your electron geometry is linear. A good way to remember linear is that 2 points form a straight line. So 2 points, 2 surrounding elements in a straight line. Linear means a line. When you have 3 electron groups, then your electron geometry is trigonal planar. So again, depending on where you are in the country, you might pronounce it differently. Trigonal planar, trigonal planar, trigonal planar, trigonal planar. It's all the same thing. Here, a good way to remember this is "tri" equals 3. It starts out with "tri", "tri" means 3, 3 electron groups. Finally, if your electron group has 4, then your electron geometry is tetrahedral. A good way to remember tetrahedral is "tetra" means 4. Right? So "tetra" here means 4, 4 electron groups. So when it comes to 2, 3, and 4 electron groups, remember we have linear, trigonal planar, and tetrahedral.