1. The problem statement, all variables and given/known data How does an electron get from an excited state (r = 4ao) to a ground state (r = ao) without being anywhere in between? 2. Relevant equations 3. The attempt at a solution My only attempt would be to say that it does exist between for a short time, and during that time it emits a photon. The book I'm working with poses the question but lends no hint toward how to answer it, it simply states the electron "jumps" between states.