The compound that is not a Lewis acid

Options

A. `AICI_3`
B. `BF_3`
C. `NF_3`
D. `SnCI_4`

Answer

To determine which compound is not a Lewis acid, we need to understand the definition of Lewis acids and bases. According to Lewis theory, a Lewis acid is a species that can accept a lone pair of electrons, while a Lewis base is a species that can donate a lone pair of electrons.

### Step-by-Step Solution:

1. **Identify the Compounds**: We need to analyze the following compounds: AlCl3, PF3, NF3, and SnCl4.

2. **Analyze AlCl3**:
- Aluminum (Al) has the electron configuration: [Ne] 3s² 3p¹.
- It can form three bonds with chlorine, and in doing so, it can promote one of its 3s electrons to the 3p orbital.
- This results in sp² hybridization, leaving an empty p orbital that can accept a lone pair of electrons from a Lewis base.
- **Conclusion**: AlCl3 is a Lewis acid.

3. **Analyze PF3**:
- Phosphorus (P) has the electron configuration: [Ne] 3s² 3p³.
- In PF3, phosphorus forms three bonds with fluorine, and it has one lone pair remaining.
- The empty p orbital can accept a lone pair, making it a potential Lewis acid.
- **Conclusion**: PF3 can act as a Lewis acid.

4. **Analyze NF3**:
- Nitrogen (N) has the electron configuration: [He] 2s² 2p³.
- In NF3, nitrogen forms three bonds with fluorine and retains one lone pair.
- There are no empty orbitals available for accepting a lone pair of electrons.
- **Conclusion**: NF3 is not a Lewis acid.

5. **Analyze SnCl4**:
- Tin (Sn) has the electron configuration: [Kr] 5s² 4d¹⁰ 5p².
- In SnCl4, tin can promote electrons and form four bonds with chlorine, resulting in sp³ hybridization.
- This leaves empty d orbitals available for accepting electrons.
- **Conclusion**: SnCl4 is a Lewis acid.

6. **Final Conclusion**: Among the compounds analyzed, NF3 is the only compound that does not act as a Lewis acid.

### Summary:
- AlCl3: Lewis acid
- PF3: Lewis acid
- NF3: **Not a Lewis acid**
- SnCl4: Lewis acid