Hello. I have recently been introduced to the concept of electrons as standing waves around the atomic nucleus. The explanation I read used the simulation of "a particle in a tube" to give a monodimensional interpretation of how the standing wave behaves. Within an atom, what serves as the "boundaries" for the electron-wave? Is it purely classical electrostatic attraction to the nucleus? Any accompanying calc-1 level math describing how classical electrostatics shapes these bounds would be very much appreciated. Thank you in advance for any replies.