Which of the following statements is correct?

Options

A. `BCl_(3) and AlCl_(3)` are both Lewis acids and `BCl_(3)`
B. Both `BCl_(3) and AlCl_(3)` are Lewis acids and `AlCl_(3)` is stronger than `BCl_(3)`
C. Both `BCl_(3) and AlCl_(3)` are equally strong Lewis acids
D. Both `BCl_(3) and AlCl_(3)` are not Lewis acids

Answer

To determine which of the statements regarding BCl3 and AlCl3 is correct, we need to analyze the properties and behavior of both compounds as Lewis acids.

### Step-by-Step Solution:

1. **Identify Lewis Acids**:
- Lewis acids are defined as species that can accept a pair of electrons. Both BCl3 and AlCl3 can accept electron pairs due to the presence of vacant orbitals.

2. **Electronic Configuration**:
- **Boron (B)**: The electronic configuration is 1s² 2s² 2p¹. In BCl3, boron forms three bonds with chlorine, using its available electrons and leaving an empty p orbital.
- **Aluminum (Al)**: The electronic configuration is 1s² 2s² 2p⁶ 3s² 3p¹. In AlCl3, aluminum also forms three bonds with chlorine, utilizing its electrons and leaving empty orbitals.

3. **Hybridization**:
- For BCl3, boron undergoes sp² hybridization, leading to a trigonal planar structure with one empty p orbital.
- For AlCl3, aluminum undergoes sp³ hybridization, resulting in a tetrahedral structure with empty d orbitals available for bonding.

4. **Comparison of Lewis Acid Strength**:
- BCl3 has a smaller atomic size compared to AlCl3, which allows for better overlap with the larger chlorine orbitals. However, the empty p orbital in BCl3 is less effective in stabilizing the electron pair compared to the empty d orbitals in AlCl3.
- The extent of overlap between the orbitals of BCl3 and Cl is not as effective as that between AlCl3 and Cl, due to the difference in atomic sizes and the period of the elements involved.

5. **Conclusion**:
- Although both BCl3 and AlCl3 are Lewis acids, BCl3 is considered to be a stronger Lewis acid than AlCl3 due to its ability to accept electron pairs more readily, despite the differences in orbital overlap.

### Final Answer:
Both BCl3 and AlCl3 are Lewis acids, but BCl3 is stronger than AlCl3.