please explain valence shell electron pair repulsion theory

Asked by GARIMA SRIVASTAVA | 19th Feb, 2011, 10:39: PM

Expert Answer:

Dear Student
 
 Valence shell electron pair repulsion theory, VSEPR, is a simple technique for predicting the shape or geometry of atomic centres in small molecules and molecular ions. 
 

Postulates

  • The shape of the molecule is determined by both the total number of electron pairs (bonding and non-bonding) around the molecules central atom and the orientation of these electron pairs in the space around the central atom.
  • In order to minimize the repulsion forces between them, electron pairs around the molecules central atom, tend to stay as far away from each other as possible.
  • Electron pairs around the molecule's central atom can be shared or can be lone pairs. The 'shared pairs' of electrons are also called bond pairs of electrons. The presence of lone pair(s) of electrons on the central atom causes some distortions in the expected regular shape of the molecule.
  • The strength of repulsions between different electron pairs follows the order:

Lone pair - Lone pair > Lone pair - Shared pair > Shared pair - Shared pair.

 
We hope that clarifies your query.
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Answered by  | 20th Feb, 2011, 09:36: PM

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