Determining the Shape of a Molecule
The best way to determine the architecture of a molecule is to:
1. Determine what the central atom is.
2. Draw the Lewis structure of the molecule.
3. Determine the number of bonding pairs and lone pairs around the central atom.
4. Refer to the following chart and determine the shape of the molecule.
 
VSEPR CHART     A = central atom   X = bonding pair   E = lone pair
# of 
Electron 
Pairs
# of 
Lone 
Pairs
VSEPR 
notation
Name Diagram
2 0  AX2 Linear 
2 2 AX2E2 Bent 
2 3 AX2E3 Linear 
3 0        AX3 Planar triangular
3 1 AX3 Trigonal pyramidal
3 2 AX3E2  T-shaped 
4 0  AX4 Tetrahedral 
4 1 AX4 See-saw
4 2  AX4E2 Square planar 
5 0 AX5 Trigonal bipyramidal 
5 1 AX5 Square pyramidal
6 0 AX6  Octahedral