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 Cl and B, the B–Cl bond is naturally polar. 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.

Answer 2

Explanation:

B-Cl has a dipole due to the difference in the elctronegativity of boron and chlorine atom. The overall dipole of a molecule also depends on the geometry. The geometry of BCl3 is planar with a bond angle of 120 degree. The resultant dipole of two B-Cl bonds cancels the third one, resulting in net zero dipole.