Asked in NUMS 2018 2018Moderate

The minimum angle between bond - pair bond is shown by:

Correct answer: B. NF3

  • A. SnCl4
  • B. NF3
  • C. SO3
  • D. H2O

Explanation

The molecule has a trigonal pyramidal structure, like ammonia. The bond angle is reduced from 107° in ammonia to 101.9° in NF3, because the very electronegative fluorines pull the electrons in the N-F bonds towards themselves, reducing interelectronic repulsions, so that the NF3 'umbrella' closes up.

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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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