Shapes of Molecules and Ions

Shapes of Molecules and Ions with Double or Triple Bonds

The presence of double or triple bonds does not complicate matters at all. In a double bond, both electron pairs must stay together between the two atoms; they can't wander off to different locations in the valence shell. This is also true for the three pairs of electrons in a triple bond. For the purposes of predicting molecular geometry, then, we can treat double and triple bonds just as we do single bonds. For example, the Lewis formula for CO₂ is

         ..         ..
         O=C=O
         ..         ..

The carbon atom has no lone pairs. Therefore, the two groups of electron pairs that make up the double bonds are located on opposite sides of the nucleus and a linear molecule is formed. Similarly, you should be able to predict the following shapes for SO₂ and SO₃