Shapes of Molecules (valence shell electron pair repulsion theory - VSEPRT)

Identify the central atom.
1. Draw a dot/cross diagram to show bonding.
  1. Count the number of electrons in the outer valence shell of the central atom.
    1. Count how many electrons the other atoms contribute to the bonding.
      1. Add them up and divide by 2 to give the number of electron pairs
        These will arrange themselves to minimise the repulsion between them.
        There are set geometries for given numbers of electron pairs.
        Lone pair - Lone pair
        Greatest repulsion
        Lone Pair - Bond pair
        Bond pair - Bond pair
        Least repulsion
2/0 - Linear - 180
1. 2/1 - V bent - 120
  1. 2/2 - V bent - 104.5
    1. Water - H2O
3/0 - TrPl - 120
1. 3/1 - TrPy - 107.8
  1. 3/2 - Tee- 90
    1. Chlorine trifluoride - ClF3
  2. Ammonia - NH3
2. Boron trifluoride - BF3
4/0 - TeHe - 109.5
1. 4/1
  1. 4/2 - SqPl - 90
5/0 - TrBi - 90/120
1. Phosphorus pentachloride - PCl5
6/0 - Oct - 90
1. sulfur hexafluoride - SF6
2/0 means 2 atoms and 0 lone pairs around central atom. 4/2 means means 4 atome and 2 lone pairs around central atom.

Resource summary

	Created by Rob Pettit about 9 years ago