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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