and since it can be any where the electron will tend to localize it's position in yes the most stable area in the neigborhood of the atom which will be some orbital or another. the unlike charges of the electron and the proton are the source of the attraction, which will normally be the impetus for the electron to fall into the ground state orbital of the atom. the electron can and will be located anywhere but it will mostly hang around in the ground state orbital unless it is energized in some way by an external energy source. in that case the electron can only absorb discrete quanta of energy so that the electron jumps to a orbital in the neighborhood of the proton that is at a higher energy level.... take the external source of energy away and the electron being attracted to the proton as a result of charge will emitt a quanta of energy as it jumps down to the lower energy orbital (it loses energy)....
again the cause it the attraction the negative charge to positive charge.

regards tim