2. - - - - - - - - - -

3. Electrons are in energy levels or electron shells. Electrons closest to the nucleus have the lowest energy. First level can hold 2 electrons. Second level can hold 8. Third level can also hold 8. (you will learn about the rest in high school) Electrons can move from one energy level to another when energy (EM Radiation) is absorbed or emitted (as photons) - - - - - - - -

4. - - Neutrons = Atomic Mass - Atomic Number Atomic Number Atomic Mass 2 For Helium it is: 4 - 2 = 2 Neutrons

5. - - - - - - Neutrons = Atomic Mass - Atomic Number 6 For Carbon it is: 12 - 6 = 6 Neutrons

6. - - - - - - - - - - - - - - - - - - Neutrons = Atomic Mass - Atomic Number For Argon it is: 40 - 18 = 22 Neutrons