Which of the following is electron deficient (Lewis acid ) ?

Options

A. `CaCl_(2)`
B. `BF_(3)`
C. `Al_(2)Cl_(6)`
D. `C Cl_(4)`

Answer

To determine which of the given compounds is electron deficient (a Lewis acid), we need to analyze the electron configuration and the valence electrons of each compound.

### Step-by-Step Solution:

1. **Understanding Electron Deficiency and Lewis Acids**:
- A Lewis acid is defined as a substance that can accept an electron pair. Typically, these substances have an incomplete octet of electrons in their valence shell.

2. **Analyzing Calcium Chloride (CaCl2)**:
- Calcium (Ca) has an atomic number of 20, with the electronic configuration:
- 1s² 2s² 2p⁶ 3s² 3p⁶ 4s².
- When it forms Ca²⁺, it loses the two 4s electrons:
- Ca²⁺: 1s² 2s² 2p⁶ 3s² 3p⁶ (8 electrons in the outer shell).
- Chloride (Cl⁻) gains an electron to complete its octet.
- Since Ca²⁺ has a complete octet, it does not behave as a Lewis acid.

3. **Analyzing Boron Trifluoride (BF3)**:
- Boron (B) has an atomic number of 5, with the electronic configuration:
- 1s² 2s² 2p¹.
- In BF3, boron shares its three valence electrons with three fluorine atoms, leading to only 6 electrons in its valence shell.
- Since boron has an incomplete octet, it is electron deficient and behaves as a Lewis acid.

4. **Analyzing Aluminum Chloride (Al2Cl6)**:
- Aluminum (Al) has an atomic number of 13, with the electronic configuration:
- 1s² 2s² 2p⁶ 3s² 3p¹.
- In Al2Cl6, each aluminum atom shares its three valence electrons with chlorine atoms, and the structure allows for the completion of the octet for aluminum.
- Therefore, Al2Cl6 does not behave as a Lewis acid.

5. **Analyzing Carbon Tetrachloride (CCl4)**:
- Carbon (C) has an atomic number of 6, with the electronic configuration:
- 1s² 2s² 2p².
- In CCl4, carbon shares its four valence electrons with four chlorine atoms, achieving a complete octet.
- Thus, CCl4 is not electron deficient and does not behave as a Lewis acid.

### Conclusion:
The only compound that is electron deficient (a Lewis acid) among the options is **BF3**.

### Final Answer:
**BF3 is the electron deficient (Lewis acid) compound.**