1. REVIEW

2. Nuclear Decay

4. Subatomic Particles Protons- plus charge In the nucleus Neutrons- neutral Electrons - negative charge Outside the nucleus 4

5. Radiation Radiation comes from the nucleus of an atom. Unstable nucleus emits a particle or energy  alpha  beta  gamma 5

6. Types of Radioactive Decay

7. Balancing Nuclear Equations In the reactants and products Atomic numbers must balance and Mass numbers must balance 7

8. Beta decay 234 234 0 Th  Pa + e 90 91  1 beta particle 8

9. Types of Radioactive Decay

15. Gamma  Radiation Pure radiation Like an X-ray but comes from the nucleus 15

16. Types of Radioactive Decay

17. Gamma radiation No change in atomic or mass number 11 B 11 B + 0  5 5 0 boron atom in a high-energy state 17

18. Types of Radioactive Decay

19. 19 Radiation Protection Shielding alpha – paper, clothing beta – lab coat, gloves gamma- lead, thick concrete Limit time exposed Keep distance from source

20. Radiation Protection 20

21. Half-Life

23. 23 Half-Life of a Radioisotope The time for the radiation level to fall (decay) to one-half its initial value decay curve 8 mg 4 mg2 mg 1 mg initial 1 half-life 2 3

24. 24 Examples of Half-Life Isotope Half life C-152.4 sec Ra-2243.6 days Ra-22312 days I-12560 days C-145700 years U-235710 000 000 years

25. Calculating Half-Life

30. 30 Learning Check The half life of I-123 is 13 hr. How much of a 64 mg sample of I-123 is left after 26 hours?

31. 31 Solution t 1/2 =13 hrs t =26 hrs 26 hours/13hours = n = 2 Original Amount =64mg Mo (t/ t 1/2 )= 64 mg (½) = 16 mg 2

32. 32 Nuclear Fission Fission large nuclei break up 235 U + 1 n 139 Ba + 94 Kr + 3 1 n + 92 0 56 36 0 Energy

33. 33 Nuclear Fission

34. 34 Nuclear Fusion Fusion small nuclei combine 2 H + 3 H 4 He + 1 n + 1 1 2 0 Occurs in the sun and other stars Energy

35. 35 Learning Check Indicate if each of the following are (1) Fission(2) fusion A.Nucleus splits B.Large amounts of energy released C.Small nuclei form larger nuclei D.Hydrogen nuclei react Energy