Octet rule: Atoms can have at most 8 electrons in their outermost energy level. In order to reach stability, atoms will gain or lose electrons to achieve a full outermost energy level (valence). refer to periodic tableperiod 1 will gain 1 electronperiod 2 will gain 2 electronperiod 13 will gain 3 electronsperiod 14 will gain or lose 4 electronsperiod 15 will lose 3period 16 will lose 2period 17 will lose 1period 18 stays neutral except Helium which is located in period 18 will gain 2 as if it were in period 2