The compound that is not a Lewis acids is

Options

A. `BF_(3)`
B. `AlCl_(3)`
C. `BaCl_(2)`
D. `SnCl_(4)`

Explanation

To determine which compound is not a Lewis acid, we need to analyze the electron configurations of the given compounds and see if they are electron deficient or have an incomplete octet.

### Step-by-Step Solution:

1. **Understanding Lewis Acids**:
- Lewis acids are defined as compounds that can accept an electron pair. They are typically electron deficient or have an incomplete octet.

2. **Analyzing Each Compound**:
- **Option 1: BF3 (Boron Trifluoride)**:
- Boron has 3 valence electrons. When it forms bonds with 3 fluorine atoms, it shares its electrons but ends up with only 6 electrons in its outer shell (3 from boron and 3 from fluorine).
- Since it has less than 8 electrons, BF3 is electron deficient and acts as a Lewis acid.

- **Option 2: AlCl3 (Aluminum Chloride)**:
- Aluminum has 3 valence electrons. In AlCl3, each chlorine atom donates one electron to form a bond, resulting in aluminum having only 6 electrons in its outer shell.
- Thus, AlCl3 is also electron deficient and acts as a Lewis acid.

- **Option 3: BaCl2 (Barium Chloride)**:
- Barium is in Group 2 and has 2 valence electrons. When it forms BaCl2, it loses its 2 electrons to become Ba²⁺, and each chlorine atom gains an electron to become Cl⁻.
- Barium achieves a stable electronic configuration and does not have an incomplete octet. Therefore, BaCl2 does not act as a Lewis acid.

- **Option 4: SnCl4 (Tin(IV) Chloride)**:
- Tin has 4 valence electrons. In SnCl4, it shares its electrons with 4 chlorine atoms. However, due to the high electronegativity of chlorine, the bond pair electrons are pulled towards chlorine, leaving tin with an effective electron deficiency.
- Hence, SnCl4 acts as a Lewis acid.

3. **Conclusion**:
- The compound that is not a Lewis acid is **BaCl2 (Barium Chloride)**.