VSEPR
Chemistry: IB Diploma Higher Level, topic 2.7.1
VSEPR Theory
VSEPR theory describes the Valence Shell Electron Pair Repulsion. The use of VSEPR theory allows for the prediction of molecular geometries.
VSEPR
- The first step in predicting the VSEPR geometry and bond angles is to accurately draw the Lewis structure of the molecule.
- Then, determine the number of bonded domains and non-bonded domains.
- Bonded domains are sometimes called charge clouds.
Bonded domains
- The number of bonded domains is the number of bonds on the central atom.
- Each of the following counts as one domain:
- One single bond (consisting of 2 electrons)
- One double bond (consisting of 4 electrons)
- One triple bond (consisting of 6 electrons)
Non-bonded domains
- Non-bonded domains are the number of lone pairs on the central atom.
- One lone pair (consisting of 2 electrons)
- One single unpaired electron (consisting of 1 lone electron)
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Bond angles
- Using the sum of bonded and non-bonded domains, the geometry and bond angles can be memorized from the chart shown.
Test yourself on VSEPR
Which of the following does NOT count as one bonded domain?
A molecule has four electron pairs around its central atom. What will its geometry be?