In which of the following case central atom-F bond has partial double bond character?

Options

A. `NF_3`
B. `CF_4`
C. `PF_3`
D. `OF_2`

Answer

To determine which of the given compounds has a central atom-F bond with partial double bond character, we will analyze the bonding in each compound: NF3, CF4, PF3, and OF2.

### Step-by-Step Solution:

1. **Analyze NF3 (Nitrogen Trifluoride)**:
- Nitrogen has 5 valence electrons (2s² 2p³).
- It forms three single bonds with fluorine (which has 7 valence electrons).
- There is a lone pair on nitrogen, and since nitrogen does not have any vacant orbitals to participate in backbonding, the N-F bond is a pure single bond.
- **Conclusion**: NF3 does not have partial double bond character.

2. **Analyze CF4 (Carbon Tetrafluoride)**:
- Carbon has 4 valence electrons (2s² 2p²).
- It forms four single bonds with fluorine.
- Carbon does not have any vacant d orbitals to allow for backbonding with fluorine.
- **Conclusion**: CF4 also has pure single bond character in the C-F bonds.

3. **Analyze PF3 (Phosphorus Trifluoride)**:
- Phosphorus has 5 valence electrons (3s² 3p³) and has vacant 3d orbitals.
- It forms three bonds with fluorine and has a lone pair.
- The vacant 3d orbitals can accept electron density from the lone pairs of fluorine, allowing for pi backbonding.
- This backbonding gives the P-F bond a partial double bond character.
- **Conclusion**: PF3 has partial double bond character in the P-F bonds.

4. **Analyze OF2 (Oxygen Difluoride)**:
- Oxygen has 6 valence electrons (2s² 2p⁴).
- It forms two bonds with fluorine and has two lone pairs.
- Oxygen does not have vacant d orbitals, so it cannot participate in backbonding.
- **Conclusion**: OF2 has pure single bond character in the O-F bonds.

### Final Answer:
The compound in which the central atom-F bond has partial double bond character is **PF3**.

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