text: what travel around the nucleus in a certain regions? have to do with biolgy,each engery level has a limited capacity for electrons. because the 1st energy level is the smallest it can hold the maximum of only 2 electrons.the 2nd level is larger and can hold a maximum of 8 electrons. the 3rd level is larger yet and can hold 18 electrons. this is a rather confused question which has nothing to do with biology. in fact, it's a question about chemistry. you are asking about energy levels of *atoms*, it seems. but what is your questiion?