Question

Which among the following has the largest dipole moment

• A. $N{H}_3$
• B. $H_{2}O$
• C. $HI$
• D. $S{O}_3$

Answer 1

The correct option is B $H_{2}O$

There is a bond dipole moment pointing from each $H$ to the $O$, making the oxygen partially negative and the hydrogen partially positive. In addition, the $O$ also has non-bonded electrons in the direction opposite the hydrogen atoms. There is thus a large molecular dipole, pointing from a positive region between the two hydrogen atoms to the negative region of the oxygen atom. The charge differences cause water molecules to be attracted to each other (the relatively positive areas being attracted to the relatively negative areas) and to other polar molecules.

For others compounds the dipole moment is not that significant when compared to water molecule.