AV

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