It's been a long time since I've had a chemistry class. I know that I used to be able to do that. Not so much anymore. But what I do remember, is that chemistry is pretty difficult to understand and makes no sense. And the all of a sudden you get a "ah-ha" moment, and it all makes sense. Maybe try reading your notes, or through the book again. Maybe you'll get something that makes it all come together.
Sorry I wasn't more help....