The correct increasing bond angles order is :

Options

A. `CIF_(3) gt PF_(3) gt NF_(3) gt BF_(3)`
B. `BF_(3) gt PF_(3) gt NF_(3) gt CIF_(3)`
C. `BF_(3) gt CIF_(3) gt PF_(3) gt NF_(3)`
D. `BF_(3) gt NF_(3) gt PF_(3) gt CIF_(3)`

Answer

To determine the correct increasing order of bond angles for the molecules BF3, NF3, PF3, and ClF3, we will analyze each molecule step by step, focusing on their hybridization and resulting bond angles.

### Step 1: Analyze BF3
- **Hybridization**:
- Valence electrons of B = 3
- Number of monovalent atoms (F) = 3
- No cationic or anionic charge.

Using the formula:
\[ \text{Hybridization} = \frac{1}{2} \left( \text{Valence electrons} + \text{Monovalent atoms} - \text{Cationic charge} + \text{Anionic charge} \right) \]
\[ \text{Hybridization} = \frac{1}{2} (3 + 3) = 3 \quad \Rightarrow \text{sp}^2 \]
- **Geometry**: Trigonal planar
- **Bond Angle**: 120°

### Step 2: Analyze NF3
- **Hybridization**:
- Valence electrons of N = 5
- Number of monovalent atoms (F) = 3

Using the formula:
\[ \text{Hybridization} = \frac{1}{2} (5 + 3) = 4 \quad \Rightarrow \text{sp}^3 \]
- **Geometry**: Tetrahedral
- **Bond Angle**: 101.9° (due to lone pair-bond pair repulsion)

### Step 3: Analyze PF3
- **Hybridization**:
- Valence electrons of P = 5
- Number of monovalent atoms (F) = 3

Using the formula:
\[ \text{Hybridization} = \frac{1}{2} (5 + 3) = 4 \quad \Rightarrow \text{sp}^3 \]
- **Geometry**: Tetrahedral
- **Bond Angle**: 109° (typical for tetrahedral geometry)

### Step 4: Analyze ClF3
- **Hybridization**:
- Valence electrons of Cl = 7
- Number of monovalent atoms (F) = 3

Using the formula:
\[ \text{Hybridization} = \frac{1}{2} (7 + 3) = 5 \quad \Rightarrow \text{sp}^3d \]
- **Geometry**: Trigonal bipyramidal (T-shaped)
- **Bond Angle**: 90° (between the bonded fluorine atoms)

### Step 5: Arrange the Bond Angles in Increasing Order
Now that we have the bond angles:
- BF3: 120°
- PF3: 109°
- NF3: 101.9°
- ClF3: 90°

The increasing order of bond angles is:
1. ClF3: 90°
2. NF3: 101.9°
3. PF3: 109°
4. BF3: 120°

### Final Answer
The correct increasing order of bond angles is:
**ClF3 < NF3 < PF3 < BF3**