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Nuclear Chemistry Chapter 25.

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Nuclear Chemistry Chapter 25.

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Presentation on theme: "Nuclear Chemistry Chapter 25."— 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 Beta Gamma

6 Radiation

7 Radiation

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
Reactants Products Starting Material Ending Material Science equivalent of Math’s =

14 Reaction Format In Math class you might say:
A – B = C In Science, we don’t 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 = 92 =

17 Alpha Decay

18 Alpha Decay

19 Alpha Decay

20 Beta Decay

21 Beta Decay

22 Beta Decay

23 Positron Emission


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

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

27 Example X

28 Example X

29 Example X


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 1 1/2 2 1/4 3 1/8 4 1/16
1 1/2 2 1/4 3 1/8 4 1/16 5 1/32

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 226Ra 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


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=mc2

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 Fusion More Examples:

50 Fusion

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=mc2

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


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 Co-60
Diagnosing and treating thyroid disorders Co-60 Treating cancer

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

64 Nuclear Power Plants

65 Nuclear Power Plants

66 Nuclear Power Plants

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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