Which is the correct order of dipole moments of `BF_(3),NF_(3)and NH_(3)`?

Options

A. `NH_3 gt BF_3 gt NH_3`
B. `BF_3 gt NF_3 gt NH_3`
C. `NH_3 gt NF_3 gt BF_3 `
D. `NF_3 gt NH_3 gt BF_3`

Answer

C

Explanation

`BF_3` has zero dipole moment.

In `NH_3` N is more electronegative than H. So, nitrogen pulls the electron from H towards itself and the direction of moment is same due to N-H bond as that of the lone pair of electrons on nitrogen.

In `NF_3` F is more electronegative than N. All F atoms pull the electrons towards themselves and resultant dipole moment is opposite to the direction of that of the lone pair at N atom. Hence, net dipole moment decreases.

Therefore, dipole moment of `NH_3` is greater than `NF_3` Hence, order of dipole moment is
`NH_3 gt NF_3 gt BF_3`