i. Dipole moment is a vector quantity.
Therefore,
The resultant dipole moment of a molecule is the vector sum of dipole moments of various bonds in the molecule.
ii. In BF3 molecule,
B-F bond is polar and has a bond dipole moment.
iii. Also, in BF3,
The three B-F bonds are oriented at an angle of 120° to one another.
iv. The resultant of any two bond moments is equal in magnitude and opposite in direction to that of third.
Hence,
The net sum is zero and the dipole moment of tetra-atomic BF3 molecule is zero.
