VSEPR theory
Model predicting molecular geometry from electron pair repulsion.
Valence shell electron pair repulsion (VSEPR) theory is a model used in chemistry to predict the geometry of individual molecules from the number of electron pairs surrounding their central atoms. It is also named the Gillespie-Nyholm theory after its two main developers, Ronald Gillespie and Ronald Nyholm, but is also called the Sidgwick-Powell theory after earlier work by Nevil Sidgwick and Herbert Marcus Powell. The premise of VSEPR is that valence electron pairs surrounding an atom tend to repel each other, and the predicted molecular geometry is the one that minimizes this repulsion.
- field
- Chemistry
- known_for
- Predicting molecular geometry from electron pair repulsion
- developers
- Ronald Gillespie, Ronald Nyholm, Nevil Sidgwick, Herbert Marcus Powell
Lore & Background
Gillespie has emphasized that the electron-electron repulsion due to the Pauli exclusion principle is more important in determining molecular geometry than electrostatic repulsion.
Reader's Guide
VSEPR theory is used to predict the arrangement of electron pairs around central atoms in molecules, especially simple and symmetric molecules. The number of electron pairs in the valence shell of a central atom is determined after drawing the Lewis structure, and the sum of bonded atoms and lone pairs is known as the steric number. The theory distinguishes between bonding and nonbonding electron pairs, with lone pair–lone pair repulsions considered stronger than lone pair–bonding pair repulsions, which in turn are stronger than bonding pair–bonding pair repulsions. The AXE method of electron counting is commonly used when applying VSEPR theory.
Did You Know?
- VSEPR theory is also named the Gillespie-Nyholm theory after its two main developers, Ronald Gillespie and Ronald Nyholm.
- The premise of VSEPR is that valence electron pairs surrounding an atom tend to repel each other, and the predicted geometry minimizes this repulsion.
- Gillespie has emphasized that the Pauli exclusion principle is more important in determining molecular geometry than electrostatic repulsion.
Frequently Asked Questions
Who is VSEPR theory?
VSEPR theory is a chemistry model that predicts the three-dimensional shape of individual molecules based on how many electron pairs surround a central atom. It goes by several names, including the Gillespie-Nyholm theory and the Sidgwick-Powell theory, after the chemists who built it up over time.
What are VSEPR theory's powers/role?
Its core job is to figure out the most stable arrangement of electron pairs around an atom by assuming those pairs push away from one another. The geometry it predicts is always the one that keeps electron-pair repulsion as low as possible.
How does VSEPR theory's story end?
VSEPR theory is a simplified model, so it works beautifully for small, main-group molecules but struggles with transition-metal complexes or cases where bonding is heavily delocalized. In practice, chemists pair it with quantum-mechanical methods when higher accuracy is needed.
Why is VSEPR theory important?
It gives students and researchers a quick, intuitive way to sketch molecular shapes without running heavy computational calculations. That makes it a foundational tool for understanding reactivity, polarity, and how molecules interact in reaction mechanisms.
Who developed VSEPR theory?
The model was shaped by four chemists: Nevil Sidgwick and Herbert Marcus Powell laid early groundwork, and Ronald Gillespie and Ronald Nyholm later formalized the modern version. That is why you will see it credited under multiple names depending on the source.
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