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 solve the question, we need to analyze the statements regarding BCl3 and AlCl3 and determine which one is correct based on the definition of Lewis acids and their properties.

### Step-by-Step Solution:

1. **Understanding Lewis Acids**:
- A Lewis acid is defined as a substance that can accept an electron pair. This means that for a compound to be classified as a Lewis acid, it must have an incomplete octet or be capable of accepting electrons to achieve a stable electronic configuration.

**Hint**: Remember that Lewis acids are electron pair acceptors.

2. **Analyzing BCl3**:
- Boron (B) has an electronic configuration of 1s² 2s² 2p¹. When it forms BCl3, boron shares its three valence electrons with three chlorine atoms. However, boron only has six electrons in its outer shell after bonding, which means it does not complete its octet. Therefore, BCl3 is electron-deficient and can accept electrons, qualifying it as a Lewis acid.

**Hint**: Check the valence electron count after bonding to determine if the octet is complete.

3. **Analyzing AlCl3**:
- Aluminium (Al) has an electronic configuration of 1s² 2s² 2p⁶ 3s² 3p¹. In AlCl3, aluminium also shares its three valence electrons with three chlorine atoms, resulting in only six electrons in its outer shell. Thus, AlCl3 is also electron-deficient and can accept electrons, making it a Lewis acid as well.

**Hint**: Compare the electron configurations and octet completion for both compounds.

4. **Comparing Strengths of Lewis Acids**:
- To determine which of BCl3 or AlCl3 is a stronger Lewis acid, we consider the atomic structure. The 2p orbital in boron is closer to the nucleus than the 3p orbital in aluminium. This proximity means that boron can attract incoming electrons more effectively than aluminium can. Therefore, BCl3 is a stronger Lewis acid compared to AlCl3.

**Hint**: Consider the distance of the orbitals from the nucleus when comparing acid strength.

5. **Evaluating the Statements**:
- **Statement 1**: BCl3 and AlCl3 are both Lewis acids. (Correct)
- **Statement 2**: AlCl3 is stronger than BCl3. (Incorrect)
- **Statement 3**: Both BCl3 and AlCl3 are equally strong Lewis acids. (Incorrect)
- **Statement 4**: Both BCl3 and AlCl3 are not Lewis acids. (Incorrect)

Based on the analysis, the only correct statement is that both BCl3 and AlCl3 are Lewis acids.

### Final Answer:
The correct statement is: **BCl3 and AlCl3 are both Lewis acids.**