VSEPR Theory
Predicts the geometry of simple molecules and polyatomic ions based on electron pair repulsion.
What is VSEPR Theory?
A region around a central atom where electrons are likely to be found. This includes single bonds, double bonds, triple bonds, and lone pairs.
Key points
- Understand the principle of electron pair repulsion.
- Determine the number of electron domains around a central atom.
- Predict the electron geometry of a molecule or ion.
- Predict the molecular geometry of a molecule or ion.
Common exam trap
Confusing electron geometry with molecular geometry.
Definitions
- Term
Electron Domain
- Meaning
A region around a central atom where electrons are likely to be found. This includes single bonds, double bonds, triple bonds, and lone pairs.
- Term
Electron Geometry
- Meaning
The spatial arrangement of all electron pairs (bonding and non-bonding) around the central atom.
- Term
Molecular Geometry
- Meaning
The spatial arrangement of only the atoms (bonded atoms) in a molecule or polyatomic ion.
- Term
Lone Pair
- Meaning
A pair of valence electrons that are not shared with another atom and are associated with only one atom.
Learning objectives
Understand the principle of electron pair repulsion.
Determine the number of electron domains around a central atom.
Predict the electron geometry of a molecule or ion.
Predict the molecular geometry of a molecule or ion.
Explain the effect of lone pairs on molecular shape and bond angles.
Prerequisites
Lewis Structures
Valence Shell Electron Configuration
Concept of Bonding and Lone Pairs
Common mistakes
Confusing electron geometry with molecular geometry.
Forgetting to account for lone pairs when determining molecular shape.
Incorrectly counting the number of electron domains.
Assuming ideal bond angles without considering lone pair effects.
Keywords
VSEPR Theory
Molecular Geometry
Electron Geometry
Lone Pairs
Bond Angles
Electron Domains
Molecular Shape
Repulsion
Practice preview
According to VSEPR theory, which of the following molecules has a linear geometry?…
easy
Consider the following molecules: (i) NH₃, (ii) H₂O, (iii) CH₄, (iv) CO₂. Which of these molecules have a molecular geometry that is different from their electron geometry?…
medium
Which of the following is NOT consistent with the VSEPR theory prediction for the molecule ICl₃?…
hard