Shapes of simple molecules 

Lone pair repulsion

• any lone pairs provide additional repulsive forces
• This changes the bone angle
• For every lone pair in a molecule, subtract 2.5 from the bond angles

  Molecule shapes can be determined by;

• Finding the number of outer shell electrons on the central atom
• Add the number on bonds
• Divide by 2
• Determine how many are bonding pairs and how many are lone pairs

  Bonding pairs determine the shape of the atom

Common molecule shapes

Linear shapes = 2 bonding pairs, 0 lone pairs, 180 degree bond angle

V-shaped = 2 bonding pairs, 2 lone pairs, 104.5 degree (109.5 - 2.5 - 2.5) bond angle

Trigonal planar = 3 bonding pairs, 0 lone pairs, 120 degree bond angle

Triangular pyramid = 3 bonding pairs, 1 lone pair, 107 degree (109.5 - 2.5) bond angle

Tetrahedral = 4 bonding pairs, 0 lone pairs, 109.5 bond angle

Trigonal bipyramidal = 5 bonding pairs, 0 lone pairs, 120 and 90 degree bond angles

Octahedral = 6 bonding pairs, 0 lone pairs, 90 degree bond angle