Which of the following compound possesses Lewis acid character?
(1) `BF_(3)` (2) `SiF_(4)` (3) `PF_(5)`
Select the correct answer using the codes given below

Options

A. 1 alone
B. 1,2&3
C. 2 & 3
D. 1&3

Answer

To determine which of the given compounds possesses Lewis acid character, we need to analyze each compound based on the definition of a Lewis acid. A Lewis acid is defined as a species that can accept an electron pair.

### Step-by-Step Solution:

1. **Analyze BF3 (Boron Trifluoride)**:
- Boron trifluoride has the formula BF3.
- Boron has only three valence electrons and forms three bonds with fluorine atoms, resulting in a total of six electrons in its valence shell.
- Since boron does not have a complete octet (which requires eight electrons), it is electron deficient.
- Additionally, boron has an empty p-orbital which allows it to accept an electron pair.
- **Conclusion**: BF3 acts as a Lewis acid.

2. **Analyze SiF4 (Silicon Tetrafluoride)**:
- Silicon tetrafluoride has the formula SiF4.
- Silicon has four valence electrons and forms four bonds with fluorine atoms, resulting in a complete octet (eight electrons).
- Although SiF4 has a complete octet, the highly electronegative fluorine atoms pull electron density towards themselves, creating a partial positive charge on silicon.
- However, SiF4 does not have an empty orbital available for accepting an electron pair.
- **Conclusion**: SiF4 does not act as a Lewis acid.

3. **Analyze PF5 (Phosphorus Pentafluoride)**:
- Phosphorus pentafluoride has the formula PF5.
- Phosphorus has five valence electrons and forms five bonds with fluorine atoms.
- This results in a total of ten electrons around phosphorus, which exceeds the octet rule, indicating that phosphorus can utilize its empty d-orbitals.
- The presence of highly electronegative fluorine atoms makes phosphorus electron deficient, allowing it to accept an electron pair.
- **Conclusion**: PF5 acts as a Lewis acid.

### Final Answer:
Based on the analysis:
- BF3 and PF5 exhibit Lewis acid character.
- SiF4 does not exhibit Lewis acid character.

Thus, the correct answer is **(1) and (3)**, or simply **Option 2** if the options provided include all three.