Boron trichloride, or BCl3, is nonpolar. The three chloride atoms have a negative charge, and the one boron in the center has an equal but positive charge.
Boron sits in the center of the molecule and has three valence electrons, so it balances out the three chlorides. This causes the optimal configuration for the chloride atoms to be a perfect triangle. The important thing in this situation is to know the shape of the molecule is a triangle with 120 degrees separating the chlorides. This means that the pull of these atoms is perfectly balanced out. Boron is rare in that it is OK with not fully filling the octet, and it is still able to create nonpolar molecules.
