Which of the following is a Lewis acid?

Options

A. `AICI_(3)`
B. `MgCI_(2)`
C. `CaCI_(2)`
D. `BaCI_(2)`

Answer

To determine which of the given options is a Lewis acid, we need to understand the definition and characteristics of a Lewis acid.

### Step-by-Step Solution:

1. **Understand the Definition of a Lewis Acid**:
- A Lewis acid is defined as a substance that can accept an electron pair from a Lewis base. This means that Lewis acids must have vacant orbitals available to accommodate the incoming electron pair.

2. **Identify the Given Options**:
- Although the options are not provided in the question, we can proceed with the understanding that we are looking for a substance that fits the definition of a Lewis acid.

3. **Analyze the Properties of Each Option**:
- For each option, check if it has vacant orbitals and the ability to accept an electron pair.
- For example, if one of the options is Aluminum Chloride (AlCl3), we can analyze its structure.

4. **Examine Aluminum Chloride (AlCl3)**:
- Aluminum (Al) has the electronic configuration of 1s² 2s² 2p⁶ 3s² 3p¹. In AlCl3, aluminum has three chlorine atoms bonded to it, and it can form a trigonal planar structure.
- The aluminum atom in AlCl3 has an incomplete octet and possesses vacant p orbitals (3p) that can accept an electron pair, making it a strong Lewis acid.

5. **Conclude the Answer**:
- Based on the analysis, if AlCl3 is one of the options, it is indeed a Lewis acid. Therefore, the correct answer is Aluminum Chloride (AlCl3).

### Final Answer:
- The Lewis acid among the given options is **Aluminum Chloride (AlCl3)**.