In which of the following molecules are all the bonds not equal ?

Options

A. `ClF_(3)`
B. `BF_(3)`
C. `AlF_(3)`
D. `NF_(3)`

Answer

To determine which of the given molecules has unequal bonds, we will analyze each molecule step by step.

### Step 1: Analyze ClF3
1. **Identify the central atom**: Chlorine (Cl).
2. **Count valence electrons**: Cl has 7 valence electrons. Each fluorine (F) has 1 valence electron, and there are 3 fluorine atoms, contributing 3 electrons.
3. **Calculate total valence electrons**:
\[ 7 (Cl) + 3 \times 1 (F) = 10 \text{ valence electrons} \]
4. **Determine steric number**:
\[ \text{Steric number} = \frac{(10 \text{ valence electrons}) - (0 \text{ lone pairs})}{2} = 5 \]
5. **Determine hybridization**: The steric number of 5 corresponds to sp³d hybridization.
6. **Determine molecular geometry**: The molecular geometry is T-shaped due to the presence of 2 lone pairs on the chlorine atom.
7. **Bond equality**: In ClF3, the two axial F-Cl bonds are longer than the equatorial F-Cl bond, indicating that the bonds are not equal.

### Step 2: Analyze BF3
1. **Identify the central atom**: Boron (B).
2. **Count valence electrons**: B has 3 valence electrons, and each of the 3 fluorine atoms contributes 1 electron.
3. **Calculate total valence electrons**:
\[ 3 (B) + 3 \times 1 (F) = 6 \text{ valence electrons} \]
4. **Determine steric number**:
\[ \text{Steric number} = \frac{(6 \text{ valence electrons}) - (0 \text{ lone pairs})}{2} = 3 \]
5. **Determine hybridization**: The steric number of 3 corresponds to sp² hybridization.
6. **Determine molecular geometry**: The molecular geometry is trigonal planar.
7. **Bond equality**: All B-F bonds in BF3 are equal.

### Step 3: Analyze AlF3
1. **Identify the central atom**: Aluminium (Al).
2. **Count valence electrons**: Al has 3 valence electrons, and each of the 3 fluorine atoms contributes 1 electron.
3. **Calculate total valence electrons**:
\[ 3 (Al) + 3 \times 1 (F) = 6 \text{ valence electrons} \]
4. **Determine steric number**:
\[ \text{Steric number} = \frac{(6 \text{ valence electrons}) - (0 \text{ lone pairs})}{2} = 3 \]
5. **Determine hybridization**: The steric number of 3 corresponds to sp² hybridization.
6. **Determine molecular geometry**: The molecular geometry is also trigonal planar.
7. **Bond equality**: All Al-F bonds in AlF3 are equal.

### Step 4: Analyze NF3
1. **Identify the central atom**: Nitrogen (N).
2. **Count valence electrons**: N has 5 valence electrons, and each of the 3 fluorine atoms contributes 1 electron.
3. **Calculate total valence electrons**:
\[ 5 (N) + 3 \times 1 (F) = 8 \text{ valence electrons} \]
4. **Determine steric number**:
\[ \text{Steric number} = \frac{(8 \text{ valence electrons}) - (1 \text{ lone pair})}{2} = 4 \]
5. **Determine hybridization**: The steric number of 4 corresponds to sp³ hybridization.
6. **Determine molecular geometry**: The molecular geometry is pyramidal due to the presence of 1 lone pair.
7. **Bond equality**: All N-F bonds in NF3 are equal.

### Conclusion
After analyzing all the molecules, we find that only in **ClF3** are the bonds not equal due to its T-shaped geometry. Therefore, the answer is **ClF3**.