John T. Moore, Ed.D., teaches chemistry at Stephen F. Austin State University in Austin, TX. He is the author of numerous books on chemistry including Chemistry for Dummies, Chemistry Essentials for Dummies, and several others; and has served as AP Chemistry reader and chemistry and physical science questions writer for the College Board for many years. Richard Langley, Ph.D., also teaches chemistry at Stephen F. Austin State University in Austin, TX. He has been a grader for the AP Chemistry exams for over 20 years and is the author and co-author of several chemistry books and research papers.