The bond angle in a water molecule is about 104.5 degrees rather than 109.5 degrees because
Correct answer: C. the two lone pairs on oxygen repel the bond pairs more strongly than bond pairs repel each other
- A. oxygen is more electronegative than hydrogen
- B. water molecules are hydrogen bonded
- C. the two lone pairs on oxygen repel the bond pairs more strongly than bond pairs repel each other
- D. the molecule is linear
Explanation
Oxygen has four electron regions, two bonding and two lone pairs, so the basic arrangement is tetrahedral, but the two lone pairs squeeze the two O-H bonds closer together than in methane. Ammonia, with only one lone pair, is compressed less, which is why its angle of 107 degrees lies between the two. The progression from methane through ammonia to water is the standard illustration of the repulsion order.
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About VSEPR Theory
Valence shell electron pair repulsion theory predicts molecular shape by arranging bonding pairs and lone pairs around a central atom to minimize repulsion. Questions cover linear, trigonal planar, tetrahedral, trigonal bipyramidal and octahedral electron geometries, bond angles and distortions caused by lone pairs. Electron geometry is not always the same as molecular shape.
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