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Differences between Valence Bond Theory (VBT) and Molecular Orbital Theory (MOT)

Aspect

Valence Bond Theory (VBT)

Molecular Orbital Theory (MOT)

Basic Concept

Describes chemical bonding as the overlap of atomic orbitals, forming localized bonds.

Describes bonding by combining atomic orbitals into molecular orbitals that are delocalized over the molecule.

Bonding Explanation

Focuses on bonds as being localized between two specific atoms.

Explains bonding by considering molecular orbitals spread across the entire molecule, meaning electrons are distributed over two or more nuclei, rather than being confined between specific atoms. 

Orbitals and Bond Formation

In VBT, hybridization concept explains the formation of covalent bonds and polyatomic molecules.  

In hybridization, the atomic orbitals of the central atom mix to form equal energy hybrid orbitals like sp, sp², sp³ that have specific geometries and bond angles. For e.g., sp for linear, sp² for trigonal planar, sp³ for tetrahedral. These hybrid orbitals overlap with the of atomic orbitals (e.g., s, p) of the combining atom to form molecules. 

Therefore, Hybridization helps describe molecular shapes and their angles.

 

According to the Molecular Orbital Theory (MOT), a covalent bond formation occurs when the atomic orbitals of two or more atoms combine to form molecular orbitals so that the combining electrons are part of whole molecule and shared between several nuclei. 

Due to the wave nature of the electron, these atomic orbitals are considered as wavefunctions, and they can combine constructively or destructively to form bonding, anti-bonding, or non-bonding molecular orbitals. Such a phenomena is described mathematically as the Linear Combination of Atomic Orbitals (LCAO) . 

The MOT provide a more detailed picture of bond formation, electron distribution, bond order, and molecular stability. However, it does not explicitly explain shape or bond angles.

Scope and limitations

Adequate for explaining simple molecules and localized bonding, containing single, double, and triple bonds. Example, methane, ethane, H2, etc.

Explains resonance structures by showing multiple valid Lewis structures where bonds are localized. 

However, it fails to explain magnetic properties (e.g., paramagnetism of O₂) or color. It is also less effective for molecules with delocalized electrons or complex bonding.

 

Ideal for understanding complex bonding, electron delocalization, and properties like paramagnetism in molecules (e.g., benzene, O₂).

It also explains color of molecules through the concept of electronic transitions between molecular orbitals and resonance as the delocalization of electrons in molecular orbitals across the entire molecule, providing a quantum mechanical perspective. 

However, it requires advanced quantum mechanical calculations and therefore, it is more complex and computationally intensive compared to VBT.

Covalent Bond
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What is Organic Chemistry?

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Atom

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Bonding In Atoms

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Covalent Bond

  • Theories on Covalent Bond Formation
  • Valence Bond Theory- Introduction and Covalent Bond Formation
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  • Hybridization- Introduction and Types
  • sp3 Hybridization of Carbon, Nitrogen, and Oxygen
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  • Features of LCAO Theory
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  • Covalent bond Characteristics - Bond Length
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Electronic Displacement in a Covalent Bond

  • Electronegativity- Introduction
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  • Inductive effect - Introduction, Types, Classification, and Representation
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Common Types of Reactions

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Drawing Organic Structures

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Functional Groups in Organic Chemistry

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Structural Isomerism

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Intermolecular Forces

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Fundamentals of Organic Reactions

  • Types of Arrows Used in Chemistry
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  • Electrophiles - Introduction, Identification and Reaction
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Reactive Intermediates

  • Carbocation - Introduction, Nature, and Types
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  • Carbanion - Introduction, Nature, and Types
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  • Free Radical - Introduction and Types of Carbon-Centred Radicals
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  • Formation of Radicals
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  • Comparing Free Radical Stability using Dissociation energies (D-H)
  • Fate of Free Radicals
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Stereoisomerism - Conformation and Configurational Isomerism

  • Conformations in Organic Chemistry - An Introduction
  • How are Conformational Isomers Depicted
  • Open Chain and Closed Chain Conformations
  • Nomenclature related to sp3-sp3 and sp3-sp2 bond rotations
  • Conformational Analysis
  • Factors affecting the stability of conformers - Stabilizing Interactions |Hyperconjugation
  • Factors affecting the stability of conformers - Stabilizing Interactions | Intramolecular Hydrogen Bonding
  • Factors affecting the stability of conformers - Stabilizing Interactions | Dipole Minimizations
  • Factors affecting the stability of conformers - Destabilizing Interactions | Steric strain
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  • Conformation in Compounds with Lone Pairs
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  • An Example of Conformation Dependent Reaction and Product Selectivity
  • Geometrical Isomerism - Introduction
  • Impact of cis-trans isomerism on physical properties
  • Impact of cis-trans isomerism on chemical reactions
  • Scope of Geometrical Isomerism in Biological Systems and Industrial Applications
  • E/Z Nomenclature in Substituted Alkenes
     

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