The ozone molecule is O_3, and each O centre contributes 6 electrons to the valence shell.
A reasonable Lewis structure would be: O=O^(+)-O^(-). Because, around the central oxygen, there are 5 electrons (2 from the double bond, 1 from the single bond, and 2 from the lone pair), we assign this centre a positive charge, and of course we can assign each terminal oxygen a negative charge alternately by resonance.
Given the Lewis structure we predict by VSEPR a bent molecule with /_O-O-O <= 120""^@. What do we find experimentally? A bent molecule with intermediate O-O bonds; /_O-O-O = 116.8""^@.
Thus, by simply knowing how to draw a Lewis structure, counting the electrons, and using VSEPR, we have predicted the structure of a gaseous molecule, which we can't see, but we can smell. I think that is pretty clever given the (short!) time we spent on the problem.
