The document discusses the structure of atoms, including shells and the nucleus containing protons and neutrons. It explains that neutrons are needed to balance the positive charges of protons and hold the nucleus together. If there are too few or many neutrons, radiation occurs as particles leave the nucleus and release energy. Radioactivity was first discovered by exposing film to uranium and was later purified by Marie Curie. The different types of radiation - alpha, beta, and gamma - have various uses such as dating, science, medicine, energy, and weapons. Nuclear fusion also occurs when atoms are stripped of electrons in plasma.

1. Radioactivity

2. III. Structure of the Atom Shells e Location inside the atom Nucleus p & n 75

3. Problem with structure Positive charges all together Solution: James Chadwick (1932) Neutrons are glue If not balanced = Radiation

4. F. Why it happens? Neutrons hold protons together Too few neutrons – Extra protons leave Too many neutrons – Extra neutrons leave Particle release energy when leave nucleus

6. H. Who purified it? Marie Curie 140

7. I. Types Alpha Beta Gamma 141

8. J. Uses Dating 143

9. Science 144

10. Medicine 145

11. Energy 145

12. Weapons

13. IV. Astronomy Plasma (atoms stripped of electrons) 109

14. Nuclear Fusion 110