 If we take an oxygen molecule, we know that's an oxygen attached to another oxygen. There's some unshared pairs of electrons that you're going to be able to put in later. And we have a linear geometry. So that affects its behavior. We have boron tetrachloride. In this molecule, boron trifluoride. We have three fluorines attached to the boron. And in this case, the angle is 120 degrees and it's planar. So that geometry is going to tell us something about the way this molecule will behave. We have a tetrahedron, which is a very common molecular structure. We have four things attached to the center and they're equal distance apart. So the angle from here to here is 109. Here to here is 109. And if I rotate this over, you can see that it looks the same. No matter how I turn it, it's symmetrical.