The compound that is not a Lewis acids is

Options

A. `BF_(3)`
B. `AlCl_(5)`
C. `BeCl_(2)`
D. `SnCl_(4)`

Answer

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 pair acceptor, meaning it is electron deficient and seeks to gain electrons to achieve a stable electron configuration.

### Step-by-Step Solution:

1. **Identify the Compounds**: We need to analyze the compounds mentioned: BF3, AlCl3, BeCl2, and SnCl4.

2. **Analyze BF3**:
- Boron trifluoride (BF3) has three fluorine atoms bonded to boron.
- Boron has only three valence electrons and does not complete its octet (it has only 6 electrons around it).
- Therefore, BF3 is electron deficient and acts as a Lewis acid.

3. **Analyze AlCl3**:
- Aluminum chloride (AlCl3) has three chlorine atoms bonded to aluminum.
- Aluminum also has three valence electrons and does not complete its octet (it has only 6 electrons around it).
- Thus, AlCl3 is also a Lewis acid.

4. **Analyze BeCl2**:
- Beryllium chloride (BeCl2) has two chlorine atoms bonded to beryllium.
- Beryllium has two valence electrons and forms two bonds with chlorine, resulting in a linear structure with only 4 electrons around it.
- BeCl2 is electron deficient and acts as a Lewis acid.

5. **Analyze SnCl4**:
- Tin(IV) chloride (SnCl4) has four chlorine atoms bonded to tin.
- Tin has four valence electrons and forms four bonds with chlorine, resulting in a complete octet (8 electrons around it).
- Since SnCl4 does not seek to accept any more electrons, it is not a Lewis acid.

6. **Conclusion**: Among the compounds analyzed, SnCl4 is the one that is not a Lewis acid.

### Final Answer:
The compound that is not a Lewis acid is **SnCl4**.