2. Radioactivity What you don’t see...... can hurt you!.

3. Isotopes Atomic MassAtomic NumberNeutronsProtonsElectrons Carbon - 12 12 6 6 6 6 Carbon- 13 13 6 7 6 6 Carbon- 14 14 6 8 6 6 - = - = -=

4. The extra neutron causes 235 U to produce the unstable 236 U. Thus causing a chain reaction that eventually leads to a big BOOM!!!

5. The splitting of a nucleus accompanied by the release of neutrons and a large amount of energy

6. The process of combining nuclei to produce a nucleus of greater mass

7. Approx. 200,000 Japanese deaths (mostly Civilians) Only 2 nuclear weapons have ever been used in war.

9. n Nuclear Reaction any change that involves nucleus

10. Radioactivity n 1896 - Antoine Henri Becquerel accidently discovered uranium ores emit invisible rays.

11. n his 2 students, Marie Curie and Pierre Curie, isolated several radioactive elements. n Marie Curie named the process by which uranium gives off rays of radioactivity – radioactive decay

12. The Atomic Nucleus Made of nucleons.. + proton & neutral - neutron. held by“strong nuclear force.”

13. STRONG NUCLEAR FORCE = force that holds the nucleus together As size of nucleus increases, a stronger force needed to hold nucleus

14. Radioisotope – unstable isotope which undergoes radioactive decay

15. Type of Decay Particle emitted Change in mass # Change in atomic # alpha decay 4 2 Hedecreases 4 decreases by 2 beta decay 0 -1 βno changeincreases by 1 positron emission 01β01βno changedecreases by 1 electron capture x-ray photon no changedecreases by 1 gamma emission 00γ00γno change

16. Radioactive Decay Nucleus unstable when too many Protons & undergoes Radioactive decay

17. Band of Stability n As long as the ratio of neutrons to protons is between 1.0 and 1.5, the atom will be stable.

18. How can these radiation be stopped?

19. Alpha Radiation n Radium - 226 decays into radon - 222 and alpha particles. 88 Ra 226 --> 86 Rn 222 + 2  4 2  4 = 2  e 4 n Alpha particles - helium nuclei Use “Radioisotope, Radio Activity &Radioactive Decay” to describe the above Nuclear Reaction The Radioisotope, Radium 226, undergoes radioactive decay to form Radon. The type of radioactivity emitted is Alpha radiation

20. Beta Radiation 38 Sr 90 --> 39 Y 90 + -    -    = -1 e 0 Beta particles - high speed e-

21. Electron Capture nucleus catches one close electron which combines with a proton to form a neutron.

22. Beta Radiation 38 Sr 90 --> 39 Y 90 + -    n High speed e - from nucleus? How is mass the same for Y 90 but the charge is greater!

23. Beta Radiation 38 Sr 90 --> 39 Y 90 + -    n Consider neutron decay... 0 n 1 --> ? + -    0 n 1 --> 1 p 1 + -   

24. * Isotopes chemically alike as protons & electrons determine chemical properties

25. Gamma Radiation n Iron - 60 decays to Co-60 & gamma particles. 26 Fe 60 --> 27 Co 60 +    +    0   = electromagnetic rad. n high energy photons.

26. Where is Radiation in our Life n Carbon – 14 dating n Nuclear Waste n X-rays n Radiation therapy for cancer

27. How they discovered Isotopes:

28. Hydrogen –Hydrogen has 3 isotopes Hydrogen-1 = “Protium” 1 1 H Hydrogen-2 = “Deuterium” 2 1 H Hydrogen-3 = “Tritium” 3 1 H

29. Nuclear Fusion Nuclear fusion - 2 small nuclei COMBINE  larger element. Fusion releases more energy than fission because only @ very high temp 40,000,000 o C fusion of hydrogen into helium keeps the sun burning.

30. Fusion n Fusion is how the sun continually produces energy. 4 1 1 H + 2 0 -1 β  4 2 He + a lot of energy

31. Fusion Fusion – the combining of atomic nuclei

32. Fission Fission – the splitting of a large nucleus

33. Fission (cont.) n Fission is what nuclear power plants use for energy. n U – 235 + a neutron = a chain reaction of neutrons and energy

34. The Thorium Decay Series 90 Th 232 --> 2  4 + 88 Ra 228 88 Ra 228 --> -    + 89 Ac 228 89 Ac 228 --> -    + 90 Th 228 90 Th 228 --> 2  4 + 88 Ra 224 88 Ra 224 --> 2  4 + 86 Rn 220 86 Rn 220 --> 2  4 + 84 Po 216 Pg 97 & 97 b

35. The Thorium Decay Series 86 Rn 220 --> 2  4 + 84 Po 216 84 Po 216 --> 2  4 + 82 Pb 212 82 Pb 212 --> -    + 83 Bi 212  or  83 Bi 212 --> 2  4 + 81 Tl 208 81 Tl 208 --> -    + 82 Pb 208 n 82 Pb 208 is stable

36. n Chernobyl n Hurt

39. Half-life Pg 96 & 97a

41. If you have 100 g of Uranium, How many half lives are needed to reach ~ 3% of the original radioactivity. 100 g  50 g  1 st ½ life 25 g  2 nd ½ life 12.5 g  3rd 4 th ½ life life 6.25 g  3.125 g 5th ½ life

42. Half – Life Problems: 1) If I have 50g of Pb-208 and it has decayed during 2 half-lives, how much is remaining? 2) If I have 25g of U-235 and it has a half-life of one day, how much will be left after a week?

43. Critical Mass & The Enola Gay Nuclear Activities Directions:Each student will hold 3, 6 or 9 ping pong balls. Divide the room into two sections. Throw one ping pong ball. The rule is that when a student is hit by one ping pong ball, three must be released randomly. 1.What happened?Why? Directions:Now put the entire class within a 3 meter radius and try again. 2.What happened?Why?

44. Transmutation conversion of an atom of one element to another can induce by striking nuclei with high velocity charged particles

45. 44 Neutron-Proton Ratio and Nuclear Stability n Example nuclides with magic numbers of nucleons includes: These proton and neutron numbers are called “Magic Numbers.” Magic numbers are: 2 8 20 28 50 82 126

47. Half-life n time needed for 1/2 of the particles to decay.

48. 1. 86 Rn 217  He + ____ 3. 234 U  He + Y + ____ Ba-140beta 56 Ba- 140  57 La 140 -1 b o + 213 4242 84 gamma

49. Radiation Practice 1) *U – 235 + → U – 235 2) Ag – 107 + → In – 111 3) N – 12 + → O -12 4) Fe – 57 + → Ni - 61

50. 7. Show the equation for the fission of Th-232 with one fission product being Mo-96 plus the release of 2 neutrons 232 90 Th  Mo + 96 1010 1010 n +n + n Pg 108 If I had 20g of U-235 & it decayed over 3 half-lives, how much would I have left?

51. 1) If I have 10g of U-235 and it has decayed over 7 half-lives, how much U-235 will I have remaining? 2) If I have 40g of Pb-208 and it has a half life of 15 seconds, how much will remain after 1 minute? 3) If I have 20g of Pt- 144 remaining after it decayed for a week. Given that it has a half-life of a day, how much did I have originally?

52. Fusion vs. Fission n There are two processes that make use of the enormous amount of energy in a nucleus: Fusion and Fission

53. Ionizing Radiation nInIonizing radiation = radiation with enough energy to knock an electron off an atom and create an ion. nXnX-rays and gamma rays will ionize almost any molecule or atom nRnRadiation is harmful, but when used carefully it can be used in medical and scientific procedures. - --

54. X-Rays in Medicine

55. n Transuranium Elements - are all elements with an atomic number of 93 or greater –all radioactive –all man-made (SYNTHETIC)

57. LeptonsUp quarks Charm quarks e+νee+νe 1udud 3|V ud | 2 cdcd 3|V cd | 2 μ+νμμ+νμ 1usus 3|V us | 2 cscs 3|V cs | 2 τ+νττ+ντ 1ubub 3|V ub | 2 cbcb 3|V cb | 2

59. 58 Nuclear Stability and Binding Energy n Example 26-1: Calculate the mass deficiency for 39 K. The actual mass of 39 K is 39.32197 amu per atom.

60. Fission & Fusion Demos Directions: Blow up a balloon. Pinch and twist in the center. Nuclear Fission! Directions: Put 2 drops of water on the overhead projector. Nuclear Fusion! Questions: 1.Why do Doctors use radioactive isotopes which have short half lives? 2.What happens to the nucleus during Nuclear Fission? 3. How many half-lives does Radon need to live out to get rid of about 87.5% of the radioactivity?

63. End here