Nuclear Chemistry

1. Nuclear Chemistry Uses, Types of radiation & decay

2. “How many times did I say it, Harold? How many times? Make sure that bomb shelter’s got a can opener--ain’t much good without a can opener,” I said.”

3. TERMS:

4. Radioisotopes • An isotope that has an unstable nucleus and undergoes radioactive decay • Isotopes are unstable if they have too many or too few neutrons compared to the number of protons. • This is called the “band of stability”.

5. Radioactive Decay • process in which an unstable nucleus loses energy by emitting radiation • spontaneous change to more stable element

6. Ionizing Radiation • changes atoms into ions • alpha, beta, gamma, x-rays

7. Non-Ionizing Radiation • does not have enough energy to ionize matter • radio waves, light waves

8. 3 Types of Nuclear Radiation 42He 0-1e EMR a b g 4 .0005 0 2+ 1- 0 Low medium high

9. Aluminum or other metals paper,wood, cloth, etc. lead

10. Law of Conservation of matter in nuclear reactions? • Law of conservation of mass applies to chemical reactions not nuclear reactions. • But we can still balance equations.

11. Natural Radioactive Decay • Alpha Decay • 42He+2 (helium nucleus) • Net effect: Mass decreases by 4 and atomic number decreases by 2

12. Alpha Decay 23490Th 23892U --> 42He + ____ 21084Po--> 42He + ____ a 20682Pb a

13. Radioactive Decay (Cont’d.) • Beta Decay • 0-1  (fast moving electrons emitted from nucleus) • Neutron turns into a proton + electron • Net effect: Mass stays same, atomic number increases by 1

14. Beta Decay 9039Y 9038Sr --> 0-1e + ____ 3617Cl--> 0-1e + ____ b 3618Ar b

15. Radioactive Decay (Cont’d.) • Gamma Decay • Only energy is released • Symbol m for “metastable” sometimes used to represent energy

16. Gamma Decay 9943Tc*m --> 00g + Notice the gamma carries away energy leaving a more stable atom behind. 9943Tc g

17. Transmutation, Fission & Fusion

18. Transmutation • synthetic production of elements by bombarding other atoms with high speed particles.

19. It is now possible to make gold from lead using transmutations. This process costs $1 million to produce just one ounce

20. 18 F 7 2 9 Transmutation Reaction: Bombardment w/ alpha particles 14N + 4He---->

21. 239U 92 Transmutation Reactions: Bombardment w/ neutron 238U + 1n ----> 92 0

22. 12C 6 1n 9Be + 4He ----> ___ + ___ 0 4 2

23. 1H 1p+ 1 1 OR A hydrogen atom is the same as a proton 18F  17O + ___ 18F  17O + ___ 8 9 9 8

24. Fission • the nucleus is split by neutrons • the fuel is uranium which is scarce

25. products are extremely radioactive and dangerous • nuclear reactors use fission for nuclear power • produces no greenhouse emissions or other gases • waste is easily contained in small area

26. E=mc2 • when an atom is split the sum of parts do not equal the original. • the difference is energy

27. Fusion • small nuclei combine to form a larger one • fuel is hydrogen which is abundant

28. E=mc2 • when two hydrogen atoms are fused together, helium is formed. • the mass of the helium atom is less than the mass of the two hydrogen atoms. • the difference is energy

29. products are less dangerous • requires a lot of energy and high temperatures to cause fusion-currently not economically feasible • found in thermonuclear bombs and stars

30. SOURCES OF RADIATION & EFFECTS

31. Sources • Background - 100 millirem/year • Natural radioactivity that is always present-Cosmic • from foods, air, Earth, building materials, etc.

32. Sources continued… • Additional • U.S. government says should be less than 500 millirems / year • smoker - 10,000 mrem / year • medical - chest x-ray: 50 mrem -dental : 20 mrem

33. Sources continued • high altitude - more exposure to cosmic • some soil & rock: U-238 decays to radon-222 (gas) or polonium-218 (solid)

34. Sources continued… • nuclear weapons testing - banned in 1963 but half the Sr-90 still in atmosphere • Sr-90 similar to calcium, gets in food chain • accumulates in bone & affects red blood cell production • causes leukemia

35. Sources continued • nuclear disasters: Chernobyl 1986

36. EFFECTS • changes living cells, especially DNA • can upset cell chemistry • cause cell death or uncontrolled growth • cancer

37. EFFECTS • Immature and rapidly dividing cells most sensitive • bone marrow, reproductive organs, intestinal lining • genetic mutations • can cause chromosome changes

38. Radiation Detectors • Scintillation Counters • Detects light emitted by atoms in detector excited from radiation • Solid-state Detectors • Detects movement of e- through a semiconductor

39. Cloud chambers • Supersaturated air condenses into white cloudy trail where radioactive particle moves • Geiger Counter • Gas ionized by radiation produces electrical signal

40. Factors Affecting Biological Damage From Radiation • Dose • Length of time of exposure • Area of body exposed • Tissue type exposed

41. Radioactivity Lab Shielding vs. Radioactivity & Distance vs. Radioactivity

42. Purpose • To determine how shielding & distance effect radiation

43. Background radiation • 21 cpm (counts per minute) Collected at 10 second intervals. So to find counts per minute, add all 6 counts

44. Distance vs. cpm

45. Shielding Counts per minute

46. Thickness of Shield vs cpm (Co-60)