M

Molecular Orbital Theory

Ψ_MO = c₁φ₁ + c₂φ₂ (LCAO)
Quick Reference
Formula / NotationΨ_MO = c₁φ₁ + c₂φ₂ (LCAO)
Also Known AsMO theory, LCAO-MO, molecular orbital model, quantum chemical bonding theory

What is Molecular Orbital Theory?

A theory describing chemical bonding in which atomic orbitals combine to form molecular orbitals that extend over the entire molecule. Bonding MOs lower energy; antibonding MOs raise energy. MO theory explains paramagnetism of O₂ and properties of conjugated systems.

Formula & Notation

Ψ_MO = c₁φ₁ + c₂φ₂ (LCAO)

Other Names / Synonyms: MO theory, LCAO-MO, molecular orbital model, quantum chemical bonding theory

Properties & Characteristics

Molecular Orbital (MO) Theory describes bonding in terms of molecular orbitals that extend over the entire molecule, formed by linear combination of atomic orbitals (LCAO). Bonding MOs are lower energy (electron density between nuclei); antibonding MOs are higher energy (node between nuclei). Bond order = (bonding − antibonding electrons)/2. MO theory successfully explains paramagnetism of O₂, the existence (or lack) of certain molecules, and UV-Vis absorption.

Uses & Applications

MO theory is essential for understanding: paramagnetism of O₂ (2 unpaired electrons in degenerate π* MOs), bonding in aromatic systems (Hückel theory), optical properties (HOMO-LUMO gap determines light absorption), metallic conductivity (band theory as MO theory in solids), and the reactivity of organic molecules in terms of frontier molecular orbitals (FMO theory).

Safety Information

No direct safety concern. MO theory predicts the wavelength of UV-Vis absorption and thus whether molecules will absorb biologically damaging UV light (sunscreens, photocarcinogens). HOMO-LUMO calculations in computational chemistry aid prediction of reactivity and toxicological properties.

Always consult the SDS/MSDS before handling any chemical. This information is for educational purposes only.

Key Facts

Term Molecular Orbital Theory
Formula Ψ_MO = c₁φ₁ + c₂φ₂ (LCAO)
Synonyms MO theory, LCAO-MO, molecular orbital model, quantum chemical bonding theory

Frequently Asked Questions

A theory describing chemical bonding in which atomic orbitals combine to form molecular orbitals that extend over the entire molecule. Bonding MOs lower energy; antibonding MOs raise energy. MO theory explains paramagnetism of O₂ and properties of conjugated systems.

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