4.2 Valence Shell Electron Pair Repulsion Theory (VSEPR)

  • The shape of covalent bonded molecules is determined by the number of valence shell electrons (lone pair and bonding) around the central atom
  • Each electron pair is positioned as far as possible from each other to minimize the force of repulsion
  • Lone pair electrons have the greatest repulsion and will spread farther apart than bonding pairs of electrons.

To Determine VSEPR shape:

  • Draw the lewis structure
  • Determine the total number of bonding pair and lone pairs around the central atom
  • “AXE” number:
      * A - central atom
      * X - “eXtra” atoms bonded to it
      * E - lone pairs around the central atom

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