1. Honors Physics Chapter 25: Subatomic Physics

2.  Nucleons  Protons and Neutrons that Make Up the Nucleus  Atomic Number (Z)  # of Protons  Atomic Mass Number (A)  # of Protons and Neutrons  A – Z = N (# of Neutrons)

3. Subatomic Physics  Element Symbol (X)  Atomic Mass (A)  Atomic Number (Z)

4. Subatomic Physics  Ex. Hydrogen  Atomic Mass = 1  Atomic Number = 1  (1 Proton)  0 Neutrons

5. Subatomic Physics  Ex. Plutonium 239  Atomic Mass = 239  Atomic Number = 94  (94 Protons)  145 Neutrons

6. Subatomic Physics  Isotope  Atomic Nuclei That Have the Expected Number of Protons Based on Their Atomic Number, but a Different Number of Neutrons

7. Subatomic Physics  Isotope

8. Subatomic Physics  Atoms are Mostly Empty Space  Radius of Nucleus ~ 1x10 -15 m  Radius of Electron Orbit ~ 1x10 -10 m  Orbit is 100,000x Bigger than Nucleus

9. Subatomic Physics  If We Applied these Dimensions to the Solar System, the Earth’s Orbit Would be ~10x Farther from the Sun than Pluto  So, Our Solar System is Relatively Much More Dense than an Atom

10. Subatomic Physics  Atomic Mass Unit (amu)  Standard to Measure Atomic Mass  Based on 12 C  1/12 of 12 C = 1 amu = 1.66x10 -27 kg

11. Subatomic Physics  Energy & Mass  Rest Energy  1 amu of mass = 931.5 MeV of Energy

12. Subatomic Physics  Nuclear Force  Protons (+) and Neutrons (neutral) Present in the Nucleus  Why Doesn’t Repulsion Break Apart the Nucleus?

13. Subatomic Physics  Strong Nuclear Force  Fundamental Force  1 of 4 (Gravity, Electromagnetic, Weak Nuclear)  Binds Nucleons Together  Independent of Electric Charge  Exists Between any Nucleons

14. Subatomic Physics  Strong Nuclear Force  Neutron / Proton Ratio Near 1:1 (N=Z)  If Number of Protons Increases, Neutron Number Must Increase Also  As Number of Protons Increase, Even Added Neutrons Cannot Overcome Electro repulsive Force

15. Subatomic Physics  Strong Nuclear Force  All Elements with More Than 83 Protons are Unstable Due to the Repulsive Force of the Combined Charges Overcoming the Strong Nuclear Force

16. Subatomic Physics  Binding Energy  In Stable Atomic Nuclei the Protons and Neutrons are Bound Together by the Strong Nuclear Force  An Amount of Energy Required to De-Stabilize the Nucleus is called “Binding Energy”

17. Subatomic Physics  Binding Energy  Because  m =  E 0 the Binding Energy Used to De-Stabilize a Nucleus Results in Additional Mass  The Sum of the Mass of the De-Stabilized Nucleus is Greater than the Mass of the Stable Nucleus  This  m is Called “Mass Defect”

18. Subatomic Physics  Mass Defect

19. Subatomic Physics  Radioactivity / Ionizing Radiation  Atoms that are Unstable Due to the Repulsive Force of the Combined Charges Overcoming the Strong Nuclear Force Disintegrate  When These Disintegrations Occur High Energy Particles and/or Waves are Released

20. Subatomic Physics  Radioactivity  Alpha Particle Radiation (  )  Beta Particle Radiation (  - )  Positron Particle Radiation (  + )  Gamma Radiation (  )

21. Subatomic Physics  Alpha Particle Radiation (  )  Alpha Particle  He Nucleus (+2)  Two Protons  Two Neutrons

22. Subatomic Physics  Alpha Particle Radiation (  )  Transmutation  The Conversion of One Element Into Another Due to Radioactive Decay

23. Subatomic Physics  Alpha Particle Radiation (  )  General Formula

24. Subatomic Physics  Alpha Particle Radiation (  )  Gamma Radiation is Also Released During Alpha Decay

25. Subatomic Physics  Beta Particle Radiation (  - )  Negatively Charged Particle (Electron)  Created When a Neutron Decays into a Proton and an Electron  Proton Number Increases by One, Beta Particle Emitted

26. Subatomic Physics  Beta Particle Radiation (  - )  General Formula

27. Subatomic Physics  Beta Particle Radiation (  - )

28. Subatomic Physics  Positron Particle Radiation (  + )  Positively Charged Particle (Electron +)  Created When a Proton Decays into a Neutron and a Positron  Proton Number Decreases by One, Positron Particle Emitted

29. Subatomic Physics  Positron Particle Radiation (  + )  General Formula

30. Subatomic Physics  Positron Particle Radiation (  + )

31. Subatomic Physics  Gamma Radiation  )  Emitted When the Energy State of a Nucleus Changes from an Excited State to a Lower Energy State  Similar to Photon, But Much Higher Energy  No Transmutation

32. Subatomic Physics  Gamma Knife  Radiation Treatment Against Cancer Tumors

33. Subatomic Physics  Ionizing Radiation Will Continue through a Series Until a Stable Nucleus is Reached

34. Subatomic Physics  Radioactive Half-Life (T 1/2 )  Each Atom of a Particular Mass of an Element Will Undergo Decay at Its Own Rate of Disintegrations Over Time  The Overall Decay Rate of an Element is Known as its Half-Life (T 1/2 )  Each Element’s Decay Rate is CONSTANT

35. Subatomic Physics  Radioactive Half-Life (T 1/2 )  The Time Required for ½ of the Nuclei of an Element to Disintegrate  Examples  3 H = 12.3 Days  60 Co = 5.2 Years  239 Pu = 24,100 Years  238 U = 4,470,000,000 Years

36. Subatomic Physics  Radioactive Half-Life (T 1/2 )  = Decay Constant

37. Radioactivity  Radioactive Half-Life (T 1/2 )

38. Radioactivity  Radioactive Half-Life (T 1/2 )

39. Radioactivity  Radioactive Half-Life (T 1/2 )

40. Radioactivity  Radioactive Half-Life (T 1/2 )

41. Radioactivity  Radioactive Half-Life (T 1/2 )

42. Radioactivity  Radioactive Half-Life (T 1/2 )

43. Radioactivity  Radioactive Half-Life (T 1/2 )

44. Subatomic Physics  Radioactivity  Number of Disintegrations / Second  Units are Becquerel (Bq)  1 Bq = 1 Disintegration / Second  Also Curie (Ci)  1 Ci = 3.7x10 10 Bq

45. Subatomic Physics  Radiation  Problem  How many protons and neutrons are there in the nucleus of…

46. Subatomic Physics  Radiation  Solution 8 Protons, 10 Neutrons 50 Protons, 70 Neutrons

47. Subatomic Physics  Radiation  Problem  An unknown nucleus contains 70 neutrons and has twice the volume of Ni-60. What is the unknown nucleus?

48. Subatomic Physics  Radiation  Solution  An unknown nucleus contains 70 neutrons and has twice the volume of Ni-60. What is the unknown nucleus?

49. Subatomic Physics  Radiation  Solution  An unknown nucleus contains 70 neutrons and has twice the volume of Ni-60. What is the unknown nucleus?

50. Subatomic Physics  Radiation  Solution  An unknown nucleus contains 70 neutrons and has twice the volume of Ni-60. What is the unknown nucleus?

51. Subatomic Physics  Radiation  Problem  What is the mass defect in amu and kg for Cobalt- 59 which has an atomic mass of 58.933198u?

52. Subatomic Physics  Radiation  Solution  What is the mass defect in amu and kg for Cobalt-59 which has an atomic mass of 58.933198u?

53. Subatomic Physics  Radiation  Problem  What is the binding energy in MeV for Al-27 with an atomic mass of 26.981539u?

54. Subatomic Physics  Radiation  Solution  What is the binding energy in MeV for Al-27 with an atomic mass of 26.981539u?  Al-27 has 13 Protons and 14 Neutrons  1 amu = 931.5MeV

55. Subatomic Physics  Radiation  Problem  What is the daughter nucleus when Na-24 undergoes  decay?

56. Subatomic Physics  Radiation  Solution

57. Subatomic Physics  Radiation  Problem  What is the daughter nucleus when N-13 undergoes  + decay?

58. Subatomic Physics  Radiation  Solution

59. Subatomic Physics  Radiation  Problem  What is the parent nucleus whose alpha decay produces the same daughter as the beta decay of Thallium-208?

60. Subatomic Physics  Radiation  Solution  What is the parent nucleus whose alpha decay produces the same daughter as the beta decay of Thallium-208?

61. Subatomic Physics  Radiation  Solution  What is the parent nucleus whose alpha decay produces the same daughter as the beta decay of Thallium-208?

62. Subatomic Physics  Radiation  Problem  To make the dial of a watch glow in the dark, 1x10 -9 kg of Radium-226 is used. The half-life is 1600 years. How many kg of radium disappear while the watch is in use for 50 years?

63. Subatomic Physics  Radiation  Solution

64. Fission

77. Radioactivity  Fusion  Two Small Atomic Nuclei Combine to Form a Larger Nucleus  Powers the Stars  Requires VERY HIGH Temperature  ~10,000,000 o C (Plasma)

78. Radioactivity  Fission  Splitting of Large Atoms  Nuclear Power  Atomic Bombs  Requires Fissile Material  Chain Reaction Releases Energy  Fusion  Combining Small Atoms  Power of the Stars  Hydrogen Bombs  Requires VERY HIGH Temperature  Formation of Larger Nucleus Releases Energy

79. Subatomic Physics  Radiation  Homework  Pages 927 - 931  Problems  8, 24, 27, 28, 48, 51, 52, 61