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Nuclear Chemistry Chapter 25. Radiation In 1896, Antoine Henri Becquerel discovered radiation by accident. His associates at the time were Marie and Pierre.

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Nuclear Chemistry Chapter 25. Radiation In 1896, Antoine Henri Becquerel discovered radiation by accident. His associates at the time were Marie and Pierre.

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Presentation on theme: "Nuclear Chemistry Chapter 25. Radiation In 1896, Antoine Henri Becquerel discovered radiation by accident. His associates at the time were Marie and Pierre."— Presentation transcript:

1 Nuclear Chemistry Chapter 25

2 Radiation In 1896, Antoine Henri Becquerel discovered radiation by accident. His associates at the time were Marie and Pierre Curie. Marie Curie gets credit for naming radioactivity.

3 Radioisotopes Nuclei of unstable isotopes are called radioisotopes. An unstable nucleus releases energy by emitting radiation during the process of radioactive decay

4 Radiation Three Types Alpha Helium Nucleus Beta Electron Gamma Light wave

5 Symbols Alpha Gamma Beta

6 Radiation

7

8 Nuclear Symbols Table O

9 Nuclear Stability For smaller atoms a ratio of 1:1 neutrons to protons helps to maintain stability C-12, N-14, O-16 For larger atoms, more neutrons than protons are required to maintain stability Pb-207, Au-198, Ta-181

10 Nuclear Stability

11 Radioactive Decay Radioisotopes will undergo decay reactions to become more stable Alpha Decay Beta Decay Positron Emission

12 Nuclear Reactions Unstable isotopes of one element are transformed into stable isotopes of a different element. They are not affected by outside factors, like temp and pressure. They can not be sped up or slowed down.

13 General Reaction Format ReactantsProducts Starting MaterialEnding Material Science equivalent of Maths =

14 Reaction Format In Math class you might say: A – B = C In Science, we dont use subtraction A B + C A breaks into B and C

15 Decay Reactions Decay reactions involve one unstable nuclei decaying (breaking down) into 2 (or more) smaller nuclei. Alpha Decay - one of the products is an alpha particle Beta Decay - one of the products is a beta particle

16 Nuclear Reactions Reactions must always Balance Mass Numbers have to balance Atomic Numbers have to balance 238 = =

17 Alpha Decay

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19

20 Beta Decay

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23 Positron Emission

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25 Transmutations Any reaction where one element is transformed into a different element Two main types Natural Artificial

26 Transmutations Natural Usually has one reactant Alpha and Beta Decay Artificial Usually has more than one reactant Particle Accelerators

27 Example X

28 X

29 X

30

31 Half Life Amount of time for half of a sample to decay into a new element Parent Atoms Undecayed atoms Daughter Atoms Decayed atoms

32 Half Life Number of Half- lives Fraction left 01 11/2 21/4 31/8 41/16 51/32

33 Half Life Number of half-lives t = amount of time elapsed T = half-life

34 Example How many half lives does it take for a sample of C-14 to be yrs old?

35 Half Life Fraction Remaining t = amount of time elapsed T = half-life

36 Example What fraction of P-32 is left after 42.9days?

37 Example How long will a sample of Rn-222 take to decay down to 1/4 of the original sample? 7.64d

38 Fraction Remaining Mass Left Original Mass =

39 Practice How much Carbon-14 was originally in a sample that contains 4g of C-14 and is years old? 32g

40 More Practice How much 226 Ra will be left in a sample that is 4800 years old, if it initially contained 408g? 51g

41 And One More…. What is the half life of a sample that started with 144g and has only 9g left after 28days? 7d

42

43 Fission Splitting of a larger atom into two or more smaller pieces Nuclear Power Plants One Example:

44 Fission

45 Energy Production Energy is produced by a small amount of mass being converted to energy E=mc 2

46 Chain Reaction Reaction that produces material that can initiate more than one reaction

47 Chain Reaction

48 Fusion Joining of two or more smaller pieces to make a larger piece Sun, Stars One Example:

49 More Examples: Fusion

50

51 Energy Production Energy is produced by a small amount of mass being converted to energy More energy is produced by fusion than any other source E=mc 2

52 Fission vs. Fusion Advantages of Fission Produces a lot of energy Can be a controlled reaction Material is somewhat abundant

53 Fission vs. Fusion Disadvantages of Fission Uses hazardous material Produces hazardous material Long Half Life Reaction can run out of control. Limited amount of fissionable material

54 Fission vs. Fusion Advantages of Fusion Lighter weight material Easily available material Produces waste that is lighter and has shorter half-life Produces more energy than fission

55 Fission vs. Fusion Disadvantages of Fusion Must be done at very high temperatures Only been able to attain 3,000,000K Have not been able to sustain stable reaction for energy production

56

57 Uses of Radioisotopes Smoke Detectors Food Irradiation Radioactive Dating Medical Tracers Nuclear Power Plants Nuclear Weapons Origin of Elements

58 Smoke Detectors Americium produces radiation that is monitored by an electrical circuit Smoke interferes with the current, triggering the alarm

59 Food Irradiation Food is exposed to radiation, killing bacteria and mold Food is cleaner and lasts longer

60 Radioactive Dating Ratio of Parent atoms to Daughter atoms provides an age Examples C-14 used to date organic material U-238 used to date geological formations

61 Medical Tracers Radioisotopes replace stable isotopes Radiation produced can be detected by machines Example I-131 is used for thyroid disorders Barium milk shakes Co-60 for Cancer

62 Radioisotopes You must know these radioisotopes and uses I-131 Diagnosing and treating thyroid disorders Co-60 Treating cancer

63 Radioisotopes You must know these radioisotopes and uses C-14 Dating living organisms Compare to C-12 U-238 Dating geologic formations Compare to Pb-206

64 Nuclear Power Plants

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67 Nuclear Weapons

68 Video Origin of Elements YouTube

69 Stability Elements 1-26 are made in the core of stars Elements 27-92, excluding 43 and 61, are made during a Supernova explosion No element larger than 83 has a stable isotope No element larger than 92 is made in nature


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