 So far so good. All right, let's try boron trichloride, which you had to think about at the end of the last video First pause the video and draw the Lewis structure for this molecule or you can get your working from when you did it before This is what you would have drawn Remember that boron is one of those funny atoms that can happily be electron deficient. So it doesn't have a full octet So how can the bonds position themselves to minimize repulsion? Well in this case, we've got three bonds If we draw two of them Linear then the third one will have to point out at 90 degrees. Is this the best that we can do? What if we shift them around to even the spacing out? Hopefully this is what you predicted in the task at the end of the last video This molecular shape with three bonds spaced out like a propeller is called trigonal planar Because the bonds point to the vertices of a triangle and they're all in the same plane So this molecule is flat The last detail to add is that if the bonds are evenly spaced then because there are 360 degrees in a circle The angle between each pair must be 120 degrees