Shape of Molecules

In class today, we learned about resonance and molecular shape. To have resonance, a compound must have multiple bonds and when you move a bond, the atom you move it to must be able to take the bond. Resonance equalizes bond length and bond strength. Below is an image exemplifying this concept:

http://www.chem.ucla.edu/harding/tutorials/resonance/draw_res_str.html

Next, discussed the shapes of molecules. The valence shell electron pair repulsion theory is used to predict molecular shape. Something to remember is that shape determines function. So, in this concept, the way the molecules arrange themselves in a space depends on the number of lone pairs and bonded entities present.

There are 5 shapes that we are focusing on. First, a tetrahedral molecule has 4 bonded entities around one central atom. A triagnol pyramidal molecule has three bonded entities and one lone pair of electrons on the central atom. Next, a bent molecule has two bonded entities with two lone pairs of electrons on the central atom. A linear molecule has two bonded entities to the central atom that does not have a lone pair. Lastly, a triagnol planar molecule has three bonded entities to the central atom and the central atom does no have any lone pairs. Here is a picture that shows a few of these:

http://cnx.org/contents/d5d1d182-3eb0-419a-bfda-3615e56fafea@1

Here are a couple helpful links that further explain these new ideas:

Molecular Geometry
Resonance