Why is BCl3 non-polar?
The BCl3 molecule is known to be trigonal planar. That means the angle between each of the bonds is 120. The reason why this is nonpolar is easiest seen with vectors. If I start at one end of a Cl bond, and then imagine adding the other two bonds as vectors, tip to tail, they will all line up into a triangle, so if you start at any point on the triangle, you will reach back to the baginning. As a result, the charge doesn’t act in any particular direction, and so the molecule is non-polar. It’s quite tricky to explain – sorry – hope that helps!
