General Chemistry: Electron Domain Geometry versus Molecular Geometry

      A molecule can have a different shape when  referring to its electron-domain geometry than when referring to its molecular geometry.  For example, sulfur dioxide, SO2,  electron-domain geometry is trigonal planar. This is because it has 3 electron domains - the 6 valence electrons for sulfur form 2 single bonds with 2 oxygen atoms and sulfur has one non-bonding lone pair.  Also related to electron-domain geometry is the fact that the sulfur has sp2 hybridization, since its geometry is trigonal planar.
    When referring to the molecular geometry for sulfur dioxide, the molecular geometry is bent.  Note that the bent shape is related to the diffence in electronegativity between sulfur and oxygen (3.5 - 2.5). Since the difference in polarity is greater than zero, SO2 is a polar molecule.  The polarity influences  the bond angle for the bent geometry. The lone pairs are not considered when determining molecular geometry, only the bonds with the atoms are considered.
If the central atom of a molecule has no lone pairs, the molecular geometry and the electron-domain geometry are the same.  For example, carbon tetrachloride, CCl4, has no lone pairs on the central carbon atom.  Its molecular geometry and its electron-domain geometry is tetrahedral.