1. 19.1Nuclear Stability and Radioactive Decay 19.2 The Kinetics of Radioactive Decay 19.3 Nuclear Transformations 19.4Detection and Uses of Radioactivity 19.5Thermodynamic Stability of the Nucleus 19.6Nuclear Fission and Nuclear Fusion 19.7Effects of Radiation

2. Review Atomic Number (Z) – number of protons Mass Number (A) – sum of protons and neutrons

3. Radioactive Decay Nucleus undergoes decomposition (or decay) to form a different nucleus.

4. Radioactive Stability Nuclides with 84 or more protons are unstable. Light nuclides are stable when Z equals A – Z (neutron/proton ratio is 1). For heavier elements the neutron/proton ratio required for stability is greater than 1 and increases with Z.

5. Radioactive Stability Certain combinations of protons and neutrons seem to confer special stability.  Even numbers of protons and neutrons are more often stable than those with odd numbers.

6. Radioactive Stability Certain specific numbers of protons or neutrons produce especially stable nuclides.  2, 8, 20, 28, 50, 82, and 126

7. The Band of Stability

8. Types of Radioactive Decay Alpha production (  ): Beta production (  ):

9. Types of Radioactive Decay Gamma ray production (  ): Positron production :

10. Types of Radioactive Decay Electron capture : Inner-orbital electron

11. Decay Series (Series of Alpha and Beta Decays)

12. Concept Check Which of the following produces a  particle? electron capture positron alpha particle beta particle

13. Rate of Decay Rate = kN The rate of decay is proportional to the number of nuclides. This represents a first- order process.

14. Half-Life Time required for the number of nuclides to reach half the original value.

15. Nuclear Particles

16. Half-Life of Nuclear Decay

17. Exercise A first order reaction is 35% complete at the end of 55 minutes. What is the value of k? k = 7.8 x 10 -3 min -1

18. Nuclear Transformation The change of one element into another.

19. A Schematic Diagram of a Cyclotron

20. A Schematic Diagram of a Linear Accelerator

21. Measuring Radioactivity Levels Geiger counter Scintillation counter

22. Geiger Counter

23. Carbon–14 Dating Used to date wood and cloth artifacts. Based on carbon–14 to carbon–12 ratio.

24. Radiotracers Radioactive nuclides that are introduced into organisms in food or drugs and whose pathways can be traced by monitoring their radioactivity.

25. Radiotracers

26. Energy and Mass When a system gains or loses energy it also gains or loses a quantity of mass. E = mc 2  m = mass defect  E = change in energy If  E is negative (exothermic), mass is lost from the system.

27. Mass Defect ( Δ m) Calculating the mass defect for :  Since atomic masses include the masses of the electrons, we must account for the electron mass. nucleus is “synthesized” from 2 protons and two neutrons.

28. Binding Energy The energy required to decompose the nucleus into its components. Iron-56 is the most stable nucleus and has a binding energy of 8.97 MeV.

29. Binding Energy per Nucleon vs. Mass Number

30. Nuclear Fission and Fusion Fusion – Combining two light nuclei to form a heavier, more stable nucleus. Fission – Splitting a heavy nucleus into two nuclei with smaller mass numbers.

31. Nuclear Fission

32. Fission Processes A self-sustaining fission process is called a chain reaction.

33. Schematic Diagram of a Nuclear Power Plant

34. Schematic Diagram of a Reactor Core

35. Nuclear Fusion

36. Biological Effects of Radiation Depend on: 1.Energy of the radiation 2.Penetrating ability of the radiation 3.Ionizing ability of the radiation 4.Chemical properties of the radiation source

37. rem (roentgen equivalent for man) The energy dose of the radiation and its effectiveness in causing biologic damage must be taken into account. Number of rems = (number of rads) × RBE rads = radiation absorbed dose RBE = relative effectiveness of the radiation in causing biologic damage

38. Effects of Short-Term Exposures to Radiation