Question

If B–Cl bond has a dipole moment, explain why BCl₃ molecule has zero dipole moment. 

Answer 1

As a result of the difference in the electronegativities of B and Cl, the B–Cl bond is polar in nature. However, the BCl₃ molecule is non-polar. This is because BCl₃ is trigonal planar in shape. It is a symmetrical molecule. Hence, the respective dipole-moments of the B–Cl bond cancel each other, thereby causing a zero-dipole moment.