Question

differentiate between Valency bond theory and valency shell electron pair repulsion theory

Answer 1

Valence Bond (VB) theory takes as its main actors the individual atoms and their own atomic orbitals. To studybonding, it tries to look at the overlap of the atomic orbitals. ... MolecularOrbital (MO) theory looks at themolecule as a whole unit, and treatsthe electrons as delocalized and shared amongst all the atoms.

Answer 2

What is the difference between Valence bond theory and the Molecular orbital theory?

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4 ANSWERS



Kevin Shen, PhD candidate, Chemical Engineering, but I actually do chemical physics

Answered Nov 2, 2016 · Upvoted by Tom Dean, Masters in Chemistry (MChem) at the University of Oxford

The two theories reflect different bonding pictures, and are appropriate for different situations.

Valence Bond (VB) theory takes as its main actors the individual atoms and their own atomic orbitals. To study bonding, it tries to look at the overlap of the atomic orbitals. As you can imagine, because the basic building block of VB are independent atoms, it is best for describing molecules that are near dissociation or when atoms are barely close enough to associate, and the picture of electrons being localized around their respective atoms is a good approximation.

Molecular Orbital (MO) theory looks at the molecule as a whole unit, and treats the electrons as delocalized and shared amongst all the atoms. The orbitals that MO tries to draw can cover the entire molecule, and hence MO tends to give a better picture of fully-bonded molecules and molecular features like resonance (where electrons are shared across multiple nuclei instead of localized like in VB theory).