Which of the following is electron deficient compound :-

Options

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

Answer

To determine which of the given compounds is electron deficient, we need to analyze the valence electrons and bonding characteristics of each compound.

### Step-by-Step Solution:

1. **Understanding Electron Deficiency**:
- Electron deficient compounds are those that have fewer than eight electrons in their valence shell. They often have vacant orbitals and can accept electrons from other species.

2. **Analyzing PF3**:
- Phosphorus (P) has 5 valence electrons.
- In PF3, phosphorus forms three bonds with fluorine atoms.
- This uses 3 of its 5 valence electrons, leaving 2 electrons as lone pairs on phosphorus.
- Since phosphorus has a complete octet (8 electrons), PF3 is not electron deficient.

3. **Analyzing ClF3**:
- Chlorine (Cl) has 7 valence electrons.
- In ClF3, chlorine forms three bonds with fluorine atoms.
- This uses 3 of its 7 valence electrons, leaving 4 electrons as lone pairs on chlorine.
- Chlorine also has a complete octet (8 electrons), so ClF3 is not electron deficient.

4. **Analyzing AlF3**:
- Aluminium (Al) has 3 valence electrons.
- In AlF3, aluminium forms three bonds with fluorine atoms.
- This uses all 3 of its valence electrons, resulting in no lone pairs on aluminium.
- Although aluminium has only 6 electrons in its valence shell, AlF3 is ionic in nature and does not exhibit electron deficiency.

5. **Analyzing BF3**:
- Boron (B) has 3 valence electrons.
- In BF3, boron forms three bonds with fluorine atoms.
- This uses all 3 of its valence electrons, resulting in no lone pairs on boron.
- Boron has only 6 electrons in its valence shell, making it electron deficient.

6. **Conclusion**:
- Among the given compounds, BF3 is the only electron deficient compound.

### Final Answer:
The electron deficient compound is **BF3**.