Shapes of molecules

• Electron pair Repulsion theory states:

  1. Each electron pair around the central atom repels all other electron pairs.
  2. Therefore, electron pairs take up positions as far apart as possible in order to minimalize repulsion.
• Central atom with 3 electron pairs:

  electron pairs arrange themselves in a triangular shape with Bond angles of 120 degrees

  This is a Trigonal Planar shape

  
• If Central atom has 4 electron pairs:

  4 electron pairs around the central atom form a tetrahedral shape

  All the bond angles in a tetrahedral are 109.5 degrees

  
• If Central atom has 5 electron pairs:

  In order to minimalize repulsion 5 electrons arrange themselves,

  3 electron pairs on central atoms on the plane form a triangle with bond angles of 120 degrees

  2 electron pairs opposite central plane (Above and Below) form a bond angles of 90 degrees

  
• If Central atom has 6 electron pairs:

  6 electrons pairs around the central atom form a octahedral shape

  1. 2 electron pairs above and below the central plane form a bond angle of 90 degrees

  2. 4 electron pairs on the central plane form a bond angle of 90 degrees