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`

Answer

To determine which of the given fluoro-compounds behaves as a Lewis base, we first need to understand the definition of a Lewis base. A Lewis base is defined as a substance that can donate a pair of electrons to form a covalent bond. This typically means that the compound must have a lone pair of electrons on its central atom.

Let’s analyze each of the fluoro-compounds provided in the question:

1. **BF3 (Boron Trifluoride)**:
- Boron has three valence electrons and forms three bonds with fluorine atoms.
- Since all three valence electrons are used to form bonds, there are no lone pairs left on the boron atom.
- Therefore, BF3 does not behave as a Lewis base.

2. **PF3 (Phosphorus Trifluoride)**:
- Phosphorus has five valence electrons. In PF3, phosphorus forms three bonds with fluorine atoms.
- This means that two of the five valence electrons are left unbonded, resulting in one lone pair on the phosphorus atom.
- Since PF3 has a lone pair, it can donate this pair of electrons, making it a Lewis base.

3. **CF4 (Carbon Tetrafluoride)**:
- Carbon has four valence electrons and forms four bonds with fluorine atoms in CF4.
- All four valence electrons are used in bonding, leaving no lone pairs on the carbon atom.
- Therefore, CF4 does not behave as a Lewis base.

4. **SiF4 (Silicon Tetrafluoride)**:
- Silicon, like carbon, has four valence electrons and forms four bonds with fluorine atoms in SiF4.
- All four valence electrons are used for bonding, resulting in no lone pairs on the silicon atom.
- Thus, SiF4 does not act as a Lewis base.

After analyzing all four compounds, we can conclude that the only compound that behaves as a Lewis base is **PF3**.

**Final Answer**: The fluoro-compound that is most likely to behave as a Lewis base is **PF3**.

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