Correct order of bond angles for the following is

Options

A. `NH_3 gt PCl_3 gt BCl_3`
B. `BCl_3 gt NH_3 gt PCl_3`
C. `BCl_3 gt PCl_3 gt NH_3`
D. `PCl_3 gt BCl_3 gt NH_3`

Explanation

To determine the correct order of bond angles for NH3 (ammonia), PCl3 (phosphorus trichloride), and PCl5 (phosphorus pentachloride), we need to analyze the molecular geometry and hybridization of each molecule.

### Step-by-Step Solution:

1. **Identify the Molecular Geometry:**
- **NH3 (Ammonia):** It has a trigonal pyramidal shape due to one lone pair on nitrogen. The bond angle is approximately 107 degrees.
- **PCl3 (Phosphorus Trichloride):** It also has a trigonal pyramidal shape due to one lone pair on phosphorus. The bond angle is slightly less than 109.5 degrees, approximately 107 degrees as well.
- **PCl5 (Phosphorus Pentachloride):** It has a trigonal bipyramidal shape with bond angles of 120 degrees in the equatorial plane and 90 degrees between the axial and equatorial positions.

2. **Determine the Hybridization:**
- **NH3:** The nitrogen atom undergoes sp3 hybridization, resulting in a tetrahedral arrangement of electron pairs, which leads to a bond angle of about 107 degrees due to the presence of a lone pair.
- **PCl3:** The phosphorus atom also undergoes sp3 hybridization, leading to a similar bond angle of approximately 107 degrees, influenced by the lone pair.
- **PCl5:** The phosphorus atom undergoes sp3d hybridization, resulting in a bond angle of 120 degrees in the equatorial plane and 90 degrees for axial bonds.

3. **Compare the Bond Angles:**
- The bond angle in PCl5 is the largest due to its trigonal bipyramidal structure.
- The bond angles in NH3 and PCl3 are similar but slightly less than that of PCl5, with NH3 having a bond angle of about 107 degrees and PCl3 having a bond angle that is slightly less than 109.5 degrees due to the presence of lone pairs.

4. **Order the Bond Angles:**
- The correct order of bond angles from largest to smallest is:
- PCl5 > PCl3 > NH3

### Final Answer:
The correct order of bond angles is: **PCl5 > PCl3 > NH3.**