Which of the of the following fluoro -compouds is most likely to beahve as a Lewis base?

Options

A. `BF_(3)`
B. `PF_(3)`
C. `CF_(4)`
D. `SiF_(4)`

Explanation

To determine which of the given fluoro-compounds behaves as a Lewis base, we need to analyze the electron configuration and the presence of lone pairs in each compound. A Lewis base is defined as an electron-rich species that can donate an electron pair.

### Step-by-Step Solution:

1. **Identify the Compounds**: The compounds given are BF3, PF3, CF4, and SiF4.

2. **Understand Lewis Base**: A Lewis base must have a lone pair of electrons available for donation.

3. **Analyze BF3**:
- **Valence Electrons**: Boron (B) has 3 valence electrons, and each Fluorine (F) has 7 valence electrons.
- **Total Valence Electrons**: 3 (B) + 3 × 7 (F) = 24 electrons.
- **Structure**: Boron forms three bonds with three fluorine atoms and has no lone pairs left.
- **Conclusion**: BF3 does not act as a Lewis base.

4. **Analyze PF3**:
- **Valence Electrons**: Phosphorus (P) has 5 valence electrons, and each Fluorine (F) has 7 valence electrons.
- **Total Valence Electrons**: 5 (P) + 3 × 7 (F) = 26 electrons.
- **Structure**: Phosphorus forms three bonds with fluorine and has 2 lone pairs remaining.
- **Conclusion**: PF3 can act as a Lewis base due to the presence of lone pairs.

5. **Analyze CF4**:
- **Valence Electrons**: Carbon (C) has 4 valence electrons, and each Fluorine (F) has 7 valence electrons.
- **Total Valence Electrons**: 4 (C) + 4 × 7 (F) = 32 electrons.
- **Structure**: Carbon forms four bonds with four fluorine atoms and has no lone pairs left.
- **Conclusion**: CF4 does not act as a Lewis base.

6. **Analyze SiF4**:
- **Valence Electrons**: Silicon (Si) has 4 valence electrons, and each Fluorine (F) has 7 valence electrons.
- **Total Valence Electrons**: 4 (Si) + 4 × 7 (F) = 32 electrons.
- **Structure**: Silicon forms four bonds with four fluorine atoms and has no lone pairs left.
- **Conclusion**: SiF4 does not act as a Lewis base.

7. **Final Conclusion**: The only compound that behaves as a Lewis base is PF3, as it has lone pairs available for donation.

### Answer:
**PF3** is the compound that is most likely to behave as a Lewis base.