Which of the following molecule has highest dipole moment?

Options

A. `BF_3`
B. `NH_3`
C. `NF_3`
D. `B_2H_6`

Answer

To determine which molecule has the highest dipole moment among the given options (BF3, NH3, NF3, and B2H6), we will analyze the molecular geometry and electronegativity differences of each molecule.

### Step-by-Step Solution:

1. **Understanding Dipole Moment**:
- The dipole moment (\( \mu \)) is a measure of the polarity of a molecule. It arises from the difference in electronegativity between atoms and the geometry of the molecule.

2. **Analyzing BF3**:
- BF3 (Boron Trifluoride) has a trigonal planar geometry due to sp² hybridization.
- The electronegativity of fluorine is higher than that of boron, creating dipole moments directed towards each fluorine atom.
- However, the symmetrical arrangement of the three fluorine atoms cancels out the dipole moments, resulting in a net dipole moment of zero.

3. **Analyzing NH3**:
- NH3 (Ammonia) has a trigonal pyramidal geometry due to sp³ hybridization.
- Nitrogen is more electronegative than hydrogen, leading to dipole moments directed towards nitrogen.
- The presence of a lone pair on nitrogen also contributes to the dipole moment, resulting in a net dipole moment that is non-zero and directed towards nitrogen.

4. **Analyzing NF3**:
- NF3 (Nitrogen Trifluoride) also has a trigonal pyramidal geometry.
- Similar to NH3, nitrogen is less electronegative than fluorine, and the dipole moments from the three fluorine atoms point towards them.
- However, the lone pair on nitrogen and the three fluorine atoms create a situation where the dipole moments partially cancel out, resulting in a lower net dipole moment compared to NH3.

5. **Analyzing B2H6**:
- B2H6 (Diborane) has a complex structure with a bridge and terminal hydrogen atoms.
- The molecular symmetry and the arrangement of hydrogen and boron lead to cancellation of dipole moments, resulting in a net dipole moment of zero.

6. **Conclusion**:
- Among BF3, NH3, NF3, and B2H6, NH3 has the highest dipole moment due to its asymmetrical shape and the presence of a lone pair on nitrogen, which directs the dipole moment towards one side.

### Final Answer:
The molecule with the highest dipole moment is **NH3** (option B).

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