Dipole moment is a measure of polarity of a bond. It is the product of charges and the distance between partial charge. Dipole moment of polar molecule containing lone pairs is vector sum of dipole of lone pair and net dipole moments of bonds. Electronegativity of F is more than that of N, thus the direction of dipole moment of N-F bond will be form F to N. So, net dipole moment of NF, found be 0.24D. Due to less electronegativity of H in ammonia, it has maximum dipole moment. Dipole moment order: NH3>NBr3>NCl3>NF3 (1.4D)(0.8D)(0.6D)(0.24D) Here, D= debye or coulomb metre.