Now draw the Lewis structure for HF. Using the Lewis structure, you drew in Q7 and the MO diagram above, how do the 2 models for bonding [Valence bond theory and MO theory) compare for the HF molecule?
The correct answer and explanation is:
Lewis Structure and Molecular Orbital (MO) Theory Comparison for HF
Lewis Structure of HF
The Lewis structure of hydrogen fluoride (HF) consists of a single bond between hydrogen (H) and fluorine (F), with three lone pairs on fluorine:
- Hydrogen has one valence electron and needs one more to complete its duet.
- Fluorine has seven valence electrons and needs one more to complete its octet.
- A single covalent bond forms between H and F, allowing both atoms to achieve stable electron configurations.
Here is the Lewis structure:
H :F:
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Comparison of Valence Bond (VB) Theory and Molecular Orbital (MO) Theory for HF
Valence Bond (VB) theory and Molecular Orbital (MO) theory provide different perspectives on bonding in HF.
- Valence Bond (VB) Theory
According to VB theory, the H–F bond forms by the overlap of the hydrogen 1s orbital with the fluorine 2p orbital. The bond is highly polarized because fluorine is much more electronegative than hydrogen, leading to a partial positive charge on hydrogen and a partial negative charge on fluorine. The bond is considered primarily covalent with some ionic character due to this electron density shift. - Molecular Orbital (MO) Theory
MO theory describes bonding in HF through the combination of atomic orbitals to form molecular orbitals. The hydrogen 1s orbital and the fluorine 2p orbital (specifically 2p_z, which aligns along the bond axis) mix to form a bonding molecular orbital (σ) and an antibonding molecular orbital (σ*). Since fluorine’s electronegativity is much higher, the bonding orbital is significantly closer in energy to fluorine’s 2p orbital. The nonbonding fluorine 2p_x and 2p_y orbitals remain unchanged, containing lone pairs.
Key Differences:
- VB theory emphasizes localized atomic orbital overlap, while MO theory considers electron delocalization across molecular orbitals.
- MO theory explains the energy differences and bonding more quantitatively, especially polarization effects.
- MO theory better predicts bond strength and character, showing HF as a strongly polarized bond with partial ionic nature.
Now, I’ll generate the Lewis structure image.
Here is the Lewis structure diagram for Hydrogen Fluoride (HF). You can see the single bond between hydrogen and fluorine, along with the three lone pairs on fluorine. Let me know if you need any modifications or further explanations!
