In Quantum Mechanics the electron does not “orbit “ the proton. It is found in the region around the proton. The space occupied by the atom is the space where we are likely to find the electron. The plots show the probability of finding the electron in different positions. These plots compare the size of the hydrogen atom when it is in its ground state (|100>) and when it is excited ( |200> and |210> ). Cuts through the middle of these density plots show the interesting shapes of the electron clouds when the atom is excited. The program Hatom2.txt is written in QuickBasic and is well documented.