Reminder …

2. Reminder… Mass # = # of protons + # of neutrons X Element Symbol A Z Atomic # = # of protons

4. Even though the nucleus of an atom is so small, the two strongest forces in nature are forced against each other • When the balance is broken, an enormous amount of radioactive energy is released

8. Alpha Decay • Cannot penetrate through paper, but as the ability to ionize molecules • Can cause cancer if inhaled • Can be accelerated in an electric or magnetic field • Uranium-233 undergoes alpha decay 233 229 4 U + Th He 92 90 2

9. Alpha Decay Practice • If a sample of 224-Pa undergoes alpha decay, what is/are the product(s)? Answer = 220-Ac

11. Beta Decay Can penetrate skin and can ionize atoms Can cause cancer Can be accelerated in an electric or magnetic field Copper-66 undergoes beta decay 66 66 0 Cu + Zn e 29 30 -1

12. Beta Decay Practice • If a sample of 234-Pa undergoes beta decay, what is/are the product(s)? Answer = 234-U

13. Similar to high-energy X-Rays • Can pass through thick metal • Does not have high ionizing power • May cause burns, cancer, or genetic mutations

14. Particle Charge Symbol Penetration  (alpha) +2 4 He 2 Skin or 1 sheet of paper  (beta) -1 0 e -1 Few sheets of Aluminum Foil  (gamma) 0  Several centimeters of Lead Summary of all particles

16. Half-Life Practice • If you have 20 grams of 224-Pa and the isotope has a half-life of 1 second, how much is left after 4 seconds? Answer = 1.25 grams If you have 20 grams of 234-Pa and the isotope has a half-life of 7 hours, how long do you have to wait until you have only 5 grams? Answer = 2 half-lives or 14 hours

17. Fission Heavy nuclei split into lighter nuclei 235U can be used as fuel in a fission reactor

18. Fusion • Collisions between 2 nuclei are difficult to achieve because the nuclei are both positively charged and repel each other • Therefore, high energy is required for fusion reactions 2 2 4 H + H He + energy 1 1 2