In which of the following bond angle is maximum ?

Options

A. `NH_(3)`
B. `PCl_(3)`
C. `BCl_(3)`
D. `PCl_(6)^(-)`

Answer

To determine which of the following compounds has the maximum bond angle, we will analyze the bond angles in each compound step by step.

### Step 1: Analyze Ammonia (NH₃)
1. **Valence Electrons**: Nitrogen (N) has 5 valence electrons. In NH₃, it forms three bonds with hydrogen (H) and has one lone pair.
2. **Steric Number**: The steric number is calculated as the sum of bond pairs and lone pairs. Here, there are 3 bond pairs and 1 lone pair, giving a steric number of 4.
3. **Hybridization**: With a steric number of 4, the hybridization is sp³.
4. **Bond Angle**: The bond angle in ammonia is approximately 107 degrees due to the presence of the lone pair which repels the bond pairs.

### Step 2: Analyze Phosphorus Trichloride (PCl₃)
1. **Valence Electrons**: Phosphorus (P) has 5 valence electrons. In PCl₃, it forms three bonds with chlorine (Cl) and has one lone pair.
2. **Steric Number**: The steric number is again 4 (3 bond pairs + 1 lone pair).
3. **Hybridization**: The hybridization is also sp³.
4. **Bond Angle**: The bond angle in PCl₃ is slightly less than 109 degrees, approximately 107 degrees, due to the larger size of chlorine atoms causing greater repulsion.

### Step 3: Analyze Boron Trichloride (BCl₃)
1. **Valence Electrons**: Boron (B) has 3 valence electrons. In BCl₃, it forms three bonds with chlorine and has no lone pairs.
2. **Steric Number**: The steric number is 3 (3 bond pairs + 0 lone pairs).
3. **Hybridization**: The hybridization is sp².
4. **Bond Angle**: The bond angle in BCl₃ is 120 degrees, characteristic of trigonal planar geometry.

### Step 4: Analyze Phosphorus Hexachloride (PCl₆⁻)
1. **Valence Electrons**: Phosphorus has 5 valence electrons, and with the addition of one electron (due to the negative charge), it has 6 valence electrons. In PCl₆⁻, it forms six bonds with chlorine and has no lone pairs.
2. **Steric Number**: The steric number is 6 (6 bond pairs + 0 lone pairs).
3. **Hybridization**: The hybridization is sp³d².
4. **Bond Angle**: The bond angle in PCl₆⁻ is 90 degrees, characteristic of octahedral geometry.

### Conclusion
After analyzing all the compounds:
- Ammonia (NH₃) has a bond angle of approximately 107 degrees.
- Phosphorus Trichloride (PCl₃) has a bond angle of approximately 107 degrees.
- Boron Trichloride (BCl₃) has a bond angle of 120 degrees.
- Phosphorus Hexachloride (PCl₆⁻) has a bond angle of 90 degrees.

The maximum bond angle is found in Boron Trichloride (BCl₃), which is 120 degrees.

### Final Answer
The compound with the maximum bond angle is **BCl₃ (C option)**.