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 1/161
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