Which one is the electron deficient compound ?

Options

A. `NCl_(3)`
B. `BCl_(3)`
C. `"CCl"_(4)`
D. `PCl_(5)`

Answer

To determine which compound is electron deficient, we need to analyze the electron count of each compound based on their valence electrons and the number of bonds formed. An electron deficient compound is one that has less than 8 electrons in its valence shell.

### Step-by-Step Solution:

1. **Identify the Compounds**: The compounds we need to analyze are \( \text{NCl}_3 \), \( \text{BCl}_3 \), \( \text{CCl}_4 \), and \( \text{PCl}_5 \).

2. **Analyze \( \text{NCl}_3 \)**:
- Nitrogen (N) has 5 valence electrons.
- Each Chlorine (Cl) has 7 valence electrons, and there are 3 Cl atoms.
- Total electrons:
- N: 5
- Cl: 3 × 7 = 21
- Total = 5 + 21 = 26 electrons.
- In \( \text{NCl}_3 \), nitrogen forms 3 bonds with chlorine, sharing 3 electrons, and has 1 lone pair.
- Total electrons around N = 8 (3 from bonds + 2 from lone pair).
- Conclusion: \( \text{NCl}_3 \) has a complete octet (8 electrons).

3. **Analyze \( \text{BCl}_3 \)**:
- Boron (B) has 3 valence electrons.
- Each Chlorine (Cl) has 7 valence electrons, and there are 3 Cl atoms.
- Total electrons:
- B: 3
- Cl: 3 × 7 = 21
- Total = 3 + 21 = 24 electrons.
- In \( \text{BCl}_3 \), boron forms 3 bonds with chlorine.
- Total electrons around B = 6 (3 from bonds).
- Conclusion: \( \text{BCl}_3 \) has less than 8 electrons (6 electrons), making it electron deficient.

4. **Analyze \( \text{CCl}_4 \)**:
- Carbon (C) has 4 valence electrons.
- Each Chlorine (Cl) has 7 valence electrons, and there are 4 Cl atoms.
- Total electrons:
- C: 4
- Cl: 4 × 7 = 28
- Total = 4 + 28 = 32 electrons.
- In \( \text{CCl}_4 \), carbon forms 4 bonds with chlorine.
- Total electrons around C = 8 (4 from bonds).
- Conclusion: \( \text{CCl}_4 \) has a complete octet (8 electrons).

5. **Analyze \( \text{PCl}_5 \)**:
- Phosphorus (P) has 5 valence electrons.
- Each Chlorine (Cl) has 7 valence electrons, and there are 5 Cl atoms.
- Total electrons:
- P: 5
- Cl: 5 × 7 = 35
- Total = 5 + 35 = 40 electrons.
- In \( \text{PCl}_5 \), phosphorus forms 5 bonds with chlorine.
- Total electrons around P = 10 (5 from bonds).
- Conclusion: \( \text{PCl}_5 \) has more than 8 electrons (10 electrons).

6. **Final Conclusion**:
- The only compound that is electron deficient (less than 8 electrons) is \( \text{BCl}_3 \).

### Answer:
The electron deficient compound is \( \text{BCl}_3 \).