I have a Mathematics teacher, who enjoys asking questions to student(s) on the subjects of Physics and Chemistry. Firstly, What holds an atom together? According to gravity, matter that orbits an object, if its terminal velocity slows down, the gravitational pull should pull the electron into the nucleus. Why isn't this the case for atoms? Also, I read in another discussion, (which I can't find) about the formula(s) for why electrons aren't pulled into the atom, and can freely jump to the different shelfs... Help!