The compound that is not a Lewis acids is

Options

A. `AlF_(3)`
B. `AlCl_(3)`
C. `BCl_(3)`
D. `SnCl_(4)`

Explanation

To determine which compound is not a Lewis acid, we first need to understand the definition of a Lewis acid. A Lewis acid is defined as an electron-deficient species that can accept an electron pair. This means that Lewis acids typically have fewer than eight electrons in their valence shell, making them hypovalent.

Now, let's analyze the options provided in the question:

1. **Aluminum trifluoride (AlF3)**:
- Aluminum (Al) is in group 13 and has 3 valence electrons.
- Fluorine (F) has 7 valence electrons, and there are three fluorine atoms.
- Total valence electrons = 3 (from Al) + 3 × 7 (from F) = 3 + 21 = 24 electrons.
- In the context of Lewis acids, AlF3 can be considered a Lewis acid because aluminum has only 6 electrons in its valence shell when bonded.

2. **Aluminum chloride (AlCl3)**:
- Similar to AlF3, aluminum has 3 valence electrons, and chlorine (Cl) has 7 valence electrons.
- Total valence electrons = 3 (from Al) + 3 × 7 (from Cl) = 3 + 21 = 24 electrons.
- AlCl3 is also a Lewis acid because aluminum again has only 6 electrons in its valence shell.

3. **Boron trichloride (BCl3)**:
- Boron (B) is also in group 13 and has 3 valence electrons.
- Total valence electrons = 3 (from B) + 3 × 7 (from Cl) = 3 + 21 = 24 electrons.
- BCl3 is a Lewis acid because boron has only 6 electrons in its valence shell.

4. **Tin(IV) chloride (SnCl4)**:
- Tin (Sn) is in group 14 and has 4 valence electrons.
- Total valence electrons = 4 (from Sn) + 4 × 7 (from Cl) = 4 + 28 = 32 electrons.
- SnCl4 has a complete octet with 8 electrons in its valence shell and does not act as a Lewis acid.

Based on the analysis, the compound that is not a Lewis acid is **Tin(IV) chloride (SnCl4)**.

**Final Answer**: SnCl4 is not a Lewis acid.