Which of the following order of dipole moment is correct for these compounds ?

Options

A. `BF_3 gt NF_3 gt NH_3`
B. `NF_(3) gt BF_3 gt NH_3`
C. `NH_3 gt NF_3 gt BF_3`.
D. `NH_3 = NF_3 gt BF_3`.

Answer

To determine the correct order of dipole moments for the given compounds, we need to analyze the molecular structure and the electronegativity of the atoms involved in each compound.

### Step-by-Step Solution:

1. **Understanding Dipole Moment**:
- The dipole moment (μ) is a vector quantity that arises from the separation of positive and negative charges in a molecule. It is influenced by the electronegativity of the atoms involved and the geometry of the molecule.

2. **Analyzing BF3 (Boron Trifluoride)**:
- Boron trifluoride has a trigonal planar structure.
- Boron is less electronegative than fluorine. However, due to the symmetrical arrangement of the three fluorine atoms around the boron atom, the dipole moments of the individual B-F bonds cancel each other out.
- **Conclusion**: The dipole moment of BF3 is 0.

3. **Analyzing NF3 (Nitrogen Trifluoride)**:
- Nitrogen trifluoride has a pyramidal structure due to the presence of a lone pair on nitrogen.
- Nitrogen is less electronegative than fluorine, which means the electron density is pulled towards the fluorine atoms.
- The lone pair on nitrogen also contributes to the dipole moment, but the overall dipole moment is not canceled out due to the asymmetrical shape.
- **Conclusion**: NF3 has a dipole moment of approximately 0.24 Debye.

4. **Analyzing NH3 (Ammonia)**:
- Ammonia also has a pyramidal structure due to the lone pair on nitrogen.
- Nitrogen is more electronegative than hydrogen, which means the electron density is pulled towards nitrogen.
- The dipole moment is directed upwards towards the nitrogen atom, resulting in a significant dipole moment.
- **Conclusion**: NH3 has a dipole moment of approximately 1.46 Debye.

5. **Comparing the Dipole Moments**:
- From the analysis:
- BF3: 0 Debye
- NF3: 0.24 Debye
- NH3: 1.46 Debye
- Therefore, the order of dipole moments from highest to lowest is:
- NH3 > NF3 > BF3

### Final Answer:
The correct order of dipole moments is: **NH3 > NF3 > BF3**.