Some of my resonance forms are different from those in the answer in the Study Guide. How come?

Resonance forms are different electronic descriptions of the same molecule. They differ only in the distribution of electrons. One can usually write resonance forms until the cows come home. The answer only gives the most important ones, or at least those that Henry and I thought were the most important.

What do you mean? How do I know when to stop?

When we stop writing new electronic structures, we make the decision that any new structures we write will be too high in energy to contribute SIGNIFICANTLY to the structure of the molecule. Obviously the word "significantly" is the key one.

How do I learn what forms are important?

Experience. As we work through the early chapters, we will learn what factors make molecules relatively stable (low energy) or unstable (high energy). It will take some time, but you'll get there.

How?

A man approached an old lady in New York City. He asked her, "How do I get to Carnegie Hall?" She replied, "Practice, practice, practice."