1. Chemistry for Changing Times 12 th Edition Hill and Kolb Chapter 11 Nuclear Chemistry: The Heart of Matter John Singer Jackson Community College, Jackson, MI © 2010 Pearson Prentice Hall, Inc.

2. 11/2 Background Radiation Three-fourths of all exposure to radiation comes from background radiation. Most of the remaining one-fourth comes from medical irradiation such as X-rays.

3. © 2010 Pearson Prentice Hall, Inc. 11/3 Radiation Damage to Cells Radiation is capable of removing electrons from cells forming ions, hence the term ionizing radiation. Molecules can also splinter into neutral fragments called free radicals. Free radicals can disrupt cellular processes.

4. © 2010 Pearson Prentice Hall, Inc. 11/4 Radiation Damage to Cells Radiation often affects the fastest growing cells and tissues such as white blood cells and bone marrow. Ionizing radiation can also disrupt DNA causing mutations.

5. © 2010 Pearson Prentice Hall, Inc. 11/5 Radiation Damage to Cells

6. © 2010 Pearson Prentice Hall, Inc. 11/6 Nuclear Equations In nuclear equations, we balance nucleons (protons and neutrons). The atomic number (number of protons) and the mass number (number of nucleons) are conserved during the reaction.

7. © 2010 Pearson Prentice Hall, Inc. 11/7 Nuclear Equations Alpha Decay

8. © 2010 Pearson Prentice Hall, Inc. 11/8 Nuclear Equations Beta Decay

9. © 2010 Pearson Prentice Hall, Inc. 11/9 Nuclear Equations

10. © 2010 Pearson Prentice Hall, Inc. 11/10 Nuclear Equations Positron emission: A positron is a particle equal in mass to an electron, but with opposite charge.

11. © 2010 Pearson Prentice Hall, Inc. 11/11 Nuclear Equations Electron capture: A nucleus absorbs an electron from the inner shell.

12. © 2010 Pearson Prentice Hall, Inc. 11/12 Nuclear Equations

13. © 2010 Pearson Prentice Hall, Inc. 11/13 Nuclear Equations

14. © 2010 Pearson Prentice Hall, Inc. 11/14 Nuclear Equations

15. © 2010 Pearson Prentice Hall, Inc. 11/15 Half-Life Half-life of a radioactive sample is the time required for ½ of the material to undergo radioactive decay.

16. © 2010 Pearson Prentice Hall, Inc. 11/16 Half-Life

17. © 2010 Pearson Prentice Hall, Inc. 11/17 Half-Life Fraction remaining = 1/2 n

18. © 2010 Pearson Prentice Hall, Inc. 11/18 Radioisotopic Dating

19. © 2010 Pearson Prentice Hall, Inc. 11/19 Radioisotopic Dating Carbon-14 dating: The half-life of carbon-14 is 5730 years. Carbon-14 is formed in the upper atmosphere by the bombardment of ordinary nitrogen atoms by neutrons from cosmic rays.

20. © 2010 Pearson Prentice Hall, Inc. 11/20 Radioisotopic Dating Tritium dating: Tritium is a radioactive isotope of hydrogen. It has a half-life of 12.26 years and can be used for dating objects up to 100 years old.

21. © 2010 Pearson Prentice Hall, Inc. 11/21 Artificial Transmutation Bombardment of stable nuclei with alpha particles, neutrons, or other subatomic particles cause new elements to form. This process is known as artificial transmutation.

22. © 2010 Pearson Prentice Hall, Inc. 11/22 Uses of Radioisotopes Tracers Radioisotopes can be easily detected through their decay products. Therefore, they can be used to trace their movement. Some uses of tracers include: Detect leaks in underground pipes. Determine frictional wear in piston rings. Determine uptake of phosphorus and its distribution in plants.

23. © 2010 Pearson Prentice Hall, Inc. 11/23 Uses of Radioisotopes Irradiation of Food Radioisotopes can destroy microorganisms that cause food spoilage.

24. © 2010 Pearson Prentice Hall, Inc. 11/24 Nuclear Medicine Radiation therapy: Nuclear radiation can be used to kill cancerous cells. Radiation is most lethal to fastest growing cells. Radiation is aimed at the cancerous tissue. Patients undergoing radiation therapy often experience nausea and vomiting, which are early signs of radiation sickness.

25. © 2010 Pearson Prentice Hall, Inc. 11/25 Nuclear Medicine Diagnostic Uses of Radiation

26. © 2010 Pearson Prentice Hall, Inc. 11/26 Nuclear Medicine Gamma ray imaging: Technetium-99m emits gamma radiation. It can be used to image the heart and other organs and tissues.

27. © 2010 Pearson Prentice Hall, Inc. 11/27 Nuclear Medicine Positron Emission Tomography (PET): A patient inhales or is injected with positron-emitting isotopes such as carbon-11 or oxygen-15. When positrons encounter electrons, they emit two gamma rays, which exit the body in opposite directions. PET scans can be used to image dynamic processes.

28. © 2010 Pearson Prentice Hall, Inc. 11/28 Penetrating Power of Radiation Alpha radiation is least penetrating and can penetrate the outer layer of skin. Alpha radiation is stopped by a sheet of paper. Beta radiation can penetrate through a few cm of skin and tissue. Beta radiation is stopped by a sheet of aluminum foil. Gamma radiation will pass right through a body. Gamma radiation requires several cm of lead to stop.

29. © 2010 Pearson Prentice Hall, Inc. 11/29 Penetrating Power of Radiation

30. © 2010 Pearson Prentice Hall, Inc. 11/30 Penetrating Power of Radiation Two means of protecting one’s self from radiation are distance and shielding. Distance: Move away from the source. The intensity of radiation decreases with increasing distance from the source. Shielding: Lead is a commonly used shield for radiation.

31. © 2010 Pearson Prentice Hall, Inc. 11/31 Energy from the Nucleus By 1905, Albert Einstein had developed his famous mass– energy equation: E = mc2E = mc2 E = Energy m = Mass c = Speed of light

32. © 2010 Pearson Prentice Hall, Inc. 11/32 Energy from the Nucleus When protons and neutrons combine to form a nucleus, a small amount of mass is converted into energy. This is known as binding energy.

33. © 2010 Pearson Prentice Hall, Inc. 11/33 Binding Energy

34. © 2010 Pearson Prentice Hall, Inc. 11/34 The Building of the Bomb Nuclear fission: Fission occurs when larger nuclei split into small nuclei.

35. © 2010 Pearson Prentice Hall, Inc. 11/35 Nuclear Chain Reaction Fission of one nucleus produces neutrons that can cause the fission of other nuclei, thus setting off a chain reaction.

36. © 2010 Pearson Prentice Hall, Inc. 11/36 Manhattan Project The Manhattan Project was launched by President Roosevelt in 1939. It consisted of four separate research teams attempting to: Sustain the nuclear fission reaction Enrich uranium Make fissionable plutonium-239 Construct a fission atomic bomb

37. © 2010 Pearson Prentice Hall, Inc. 11/37 Manhattan Project Atomic Bomb

38. © 2010 Pearson Prentice Hall, Inc. 11/38 Manhattan Project Mushroom cloud over Nagasaki from the detonation of “Fat Man,” August 9, 1945.

39. © 2010 Pearson Prentice Hall, Inc. 11/39 Radioactive Fallout Many radioactive isotopes are produced in a nuclear bomb blast. Some are particularly harmful to humans. Among these are strontium- 90 and iodine-131. Strontium-90: Has a half-life of 28.5 years and is chemically similar to calcium. It is obtained from dairy and vegetable products and accumulates in bone. Iodine-131: Has a half-life of 8 days. It concentrates in the thyroid glands.

40. © 2010 Pearson Prentice Hall, Inc. 11/40 Nuclear Power Plants Civilian nuclear power plants use less enriched uranium (2.5-3.5% uranium-235 rather than 90% for weapons). The nuclear chain reaction is controlled for the slow release of heat energy. The heat is used to make steam, which turns a turbine to produce electricity.

41. © 2010 Pearson Prentice Hall, Inc. 11/41 Thermonuclear Reactions Nuclear fusion is a thermonuclear reaction. Smaller atomic nuclei are fused into larger nuclei in such a reaction. The principle reaction on the sun is one such reaction.

42. © 2010 Pearson Prentice Hall, Inc. 11/42 The Nuclear Age