If $B-Cl$ bond has a dipole moment,explain why $BCl_3$ molecule has zero dipole moment.

(N/A) Due to the difference in electronegativities of $B$ and $Cl$ atoms,the $B-Cl$ bond is polar in nature.
However,the $BCl_3$ molecule is non-polar. This is because $BCl_3$ has a trigonal planar geometry,which is a highly symmetrical shape.
In this structure,the three $B-Cl$ bond dipoles are oriented at an angle of $120^{\circ}$ to each other. The resultant dipole moment of any two $B-Cl$ bonds is equal and opposite to the third $B-Cl$ bond dipole.
Consequently,the individual bond dipoles cancel each other out,resulting in a net dipole moment of $\mu = 0$ for the $BCl_3$ molecule.