Example One:
 Consider the structure methane, CH4. The Lewis Dot Structure of this system indicates that there are four groups bonded to the central carbon.

 The geometry of the system has six bond angles between the external Hydrogens and the central Carbon where the angles are all 109.50.

  • This system needs to produce four orbitals that point to the corners of a tetrahedron, positions where the Hydrogen atoms are bonded.
  • Experimental information has shown that all four bonds in this structure are identical, implying that they are made in exactly the same way.
 In order to produce four identical hybrid orbitals it is necessary to hybridize four atomic orbitals. The Carbon atom has four valence atomic orbitals, one s orbital and three p orbitals. When these orbitals are hybridized, they will produce four identical hybrid orbitals.
   The hybrids will consist of 75% p character and 25% s character. Consequently, they should look much more like p orbitals than like s orbitals. All four hybrid orbitals will be identical and point to the corners of a tetrahedron. It is helpful to monitor their formation by diagraming them and recording their relative locations on an energy level diagram.

 The new orbitals are called sp3 hybrids. The name helps to identify their composition. In this case, the system has produced four sp3 hybrids of the shape indicated below.

 Notice that each hybrid has quite a bit of p character. This is indicated by the similarity the shape is to the original p orbitals. The rounded quality of the one large lobe corresponds to the fact that the orbital has 25% s character, or spherical quality.

   Based on this hybridization process, the final picture of the molecule will be approximated by this drawing. The Hydrogens have s orbitals represented as the red spheres. They attach to the hybrids at the tips of the hybrid lobes. This is because the areas of maximum electron density will always be at the tips of the lobes. When covalent bonds are formed, they will try to utilize the areas of maximum electron density. Also notice that the overall geometry of the system is a tetrahedron with the desired bond angles.

 Questions and comments should be sent to :
   kdrews@bcpl.net  
Updated March1 1, 2001