The dipole moments of `NH_3, NF_3` and `H_2O` are in the order.

Options

A. `NH_3ltNF_3ltH_2O`
B. `NH_3ltNF_3=H_2O`
C. `NF_3ltNH_3ltH_2O`
D. `NF_3ltH_2OltNH_3`

Explanation

To determine the order of dipole moments for the molecules NH₃ (ammonia), NF₃ (nitrogen trifluoride), and H₂O (water), we need to analyze the molecular geometry and electronegativity of the atoms involved.

### Step 1: Analyze the molecular structures
- **NH₃ (Ammonia)**: The nitrogen atom is at the center with three hydrogen atoms bonded to it. The molecule has a trigonal pyramidal shape due to the presence of a lone pair on nitrogen. The dipole moments from the N-H bonds do not cancel out, resulting in a net dipole moment directed towards the nitrogen.

- **NF₃ (Nitrogen Trifluoride)**: Similar to NH₃, NF₃ also has a trigonal pyramidal shape. However, the electronegativity of fluorine is higher than that of nitrogen, which means the dipole moments of the N-F bonds point towards the fluorine atoms. The dipole moments in NF₃ tend to cancel out more than in NH₃, leading to a smaller net dipole moment.

- **H₂O (Water)**: Water has a bent molecular shape due to two lone pairs on the oxygen atom. The O-H bonds are highly polar due to the high electronegativity of oxygen, and the dipole moments do not cancel out. This results in a significant net dipole moment directed towards the oxygen.

### Step 2: Compare the dipole moments
- **NH₃** has a significant dipole moment due to the polar N-H bonds and the geometry that does not allow for cancellation.
- **H₂O** has an even larger dipole moment because of the bent shape and the high electronegativity of oxygen.
- **NF₃** has the smallest dipole moment because the dipole moments of the N-F bonds largely cancel each other out.

### Conclusion
Based on the analysis:
- The order of dipole moments is: **H₂O > NH₃ > NF₃**.

### Final Answer
The correct order of dipole moments is **H₂O > NH₃ > NF₃**.

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