Here we're going to say that central elements with 3 electron groups can have either 0 or one lone pair, which gives us 2 possible molecular geometries. Alright. So we have 3 electron groups, and the possibilities are you have 3 bonding groups, surrounding elements, and 0 lone pairs. Or you could have 2 bonding groups and 1 lone pair. Remember, adding up your bonding groups and your lone pairs together gives you back the number of electron groups. So with 3 bonding groups and 0 lone pairs, we have this example. Carbon is connected to 3 surrounding elements. The visual representation will be our central element in black and these 3 surrounding elements. Here, this would be trigonal or trigonal planar, or planar. Let's look at when you have 2 bonding groups and 1 lone pair.
Here we have tin in the center. It has 2 bonding groups in the form of those chlorines, and it has 1 lone pair. Here, the representation would look like this. Here, you would have to add in the fact that the lone pair is there, which is causing this bending of the bond. Now this particular shape goes by a few different names. You might see it written as bent. Others might see it written as V-shaped, or you might see it as angular. Now the first two kind of make sense. It's not a straight line; it's bent. Also, V-shape makes sense because it's an upside-down V. Angular is a little bit tricky, but realize here that any one of these three names are associated with this particular shape where you have 2 bonding groups and one lone pair on the central element. And remember, when you have 3 electron groups total, you can either have this as your molecular geometry or this as your molecular geometry.