3. 1896—Becquerel Accidently discovered radioactivity Uranium in a drawer 1903—Marie (and Pierre) Curie Able to prove rays came from rock Coined the term “radiation” 1903—Nobel Prize —Becquerel & Curies 1911—Nobel Prize —Marie Curie

4. Radioactivity the process by which nuclei emit particles and high- energy rays Radiation the particles and high energy rays emitted during radioactivity Nuclear Chemistry the study of radioactivity

5. One atom transmutates into a different element Radioactivity caused by unstable nucleus (DECAY) LARGE amounts of energy emitted Temperature and pressure DO NOT affect the rate of reaction Multiple atoms/compounds Types of atoms never change Chemical bonding caused by unstable valence e- config. small amounts of energy (comparatively) Temp and pressure affect the rate of reaction

6. Complete Atomic Designation I 53 125– …gives very precise info about an atomic particle mass # atomic # charge (if any) element symbol Goiter due to lack of iodine iodine is now added to salt

7. Nuclear reactions are caused by an unstable nucleus. The nucleus becomes stable through decay. Before we decay, let’s review… IsotopeProtonsNeutronsAtomic No.Mass No.Symbol Uranium-235 92238 Radium-226 7853 92 14392 235 235 U 92 Uranium-238 146 92 238 U 92 234 Th 90 Thorium-234 90 14490 234 88 13888 226 226 Ra 88 Iodine-131 53 131 131 I 53 Now…Let’s decay…

8. Radioactive Skittles You have 3 radioactive skittles in front of you: Red: α rad.Orange: β rad. Yellow:  rad. One must go in your hand, one must go in your pocket, and the last one must be eaten… What arrangement will cause you the least harm??? Radiation

9. Murder with Alpha Decay In November 2006, former Russian agent Alexander Litvinenko was poisoned with radioactive Polonium at a Sushi Bar in England. News Video

10. Radioactive Decay For nuclear equations, mass (top) and atomic number (bottom) must balance. alpha (  ) decay:  -particle (i.e., a He nucleus): massive, slow-moving; stopped by paper or clothing CANNOT penetrate skin 234 92 U 230 90 Th+ 4 2 He (atomic number decreases by two)

11. beta (  ) decay:  -particle (i.e., a fast-moving electron): tiny mass blocked by wood or aluminum foil stops~1 cm into body 234 91 Pa 234 92 U+ 0 –1 e (atomic number increases by one) In  -decay, the net effect is that a n 0 is converted into a p + and an e –. The e – is then released… 1 0 n 1 1 p+ 0 –1 e *NOTE: A neutron is not actually made up of a p + and an e -, because there are no e - in the nucleus!

12. gamma radiation (  ): can penetrate to internal organs gamma ray: emitted when nucleons rearrange into a more stable configuration gamma radiation often accompanies other nuclear decay consists of high-energy photons 0 0  (or just  ) 234 92 U 230 90 Th+ 4 2 He + 0 0  2

14. Recap: Types of Radiation Alpha Beta Gamma Composition Helium nucleus Electron High energy wave Symbol  4 He 2 -1 e  0 0 0  Charge 2+ 1- No charge Mass ~ 4 amu 1/1837 amu No mass Penetrating Power Low Moderate Very High

15. Transmutation Reactions The conversion of an atom from one element to another element 1.Radioactive decay (emission) 2.Particles bombarding the nucleus of an atom

16. Alf-a Decay Po 218 84 He 2 4 + Pb 82 214 Pa 231 He 2 4 + Ac 89 227 91 Write a transmutation equation for the alpha decay of francium-208. Fr 208 He 2 4 + At 85 204 87 Write a transmutation equation for the alpha decay of radon-222. Rn 222 He 2 4 + Po 84 218 86

17. Beta Emission Pb 210 82 e 0 + Bi 83 210 Se 75 e 0 + Br 35 75 34 Write a transmutation equation for the beta emission of argon-37. Ar 37 e 0 + K 19 37 18 Write a transmutation equation for the beta emission of carbon-14. C 14 e 0 + N 7 14 6

18. Stable Isotope Radioactive materials will continue to decay until they reach a stable material (Usually with an atomic number less than 83.)

19. There are two forces at work in the nucleus: 1.Strong Nuclear Force – All subatomic particles in very close proximity will attract each other (protons and neutrons) 2.Electromagnetic Repulsions – Particles of similar charges repel each other Neutrons act as “glue” holding the nucleus together. Therefore, there must be a balance between protons and neutrons. An imbalance causes nuclear instability… Nuclear Transformations

20. Band of Stability Below the belt: Too many p +, not enough n 0 Above the belt: Too many n 0, not enough p +

22. Sources of Radiation 80% from Natural Sources 20% Man made from x-rays and consumer products

24. Half-Life Decay (t 1/2 ) The time required for one-half of the nuclei of a radioisotope sample to decay to products a. Independent of T, P, and concentration b. Useful in radioactive dating

25. Half-lives can be as short as a fraction of a second or billions of years. Different nuclei have different decay patterns, depending on why they are unstable (i.e. too many protons, too many neutrons, )

27. Carbon-14 emits beta radiation and decays with a half-life of 5730y. Assume you start with a mass of 2.00g of carbon-14. a. How long is 3 half-lives? b. How many grams will remain at the end of 3 half lives? c. How many years will it take for only 0.0625g to remain? a.t 1/2 = 5730y, 3(5730y) = 17190y b. 2.00g 1 1.00g 2 0.50g 3 0.25g 1 0.0625g 2 0.125g 3 0.25g 4 0.50g 5 1.00g c. 2.00g t 1/2 = 5730y, 5(5730y) = 28650y

28. t ½ equation 2.00g 1 1.00g 2 0.50g 3 0.25g 2.00g(1/2)(1/2)(1/2) m i (1/2) n = m f If 150.0 g of a radioactive substance undergoes 25 half lives, how many g will remain? 150.0 g (1/2) 25 = 4.47 x 10 -6 g or 2.00(1/2) 3 = 0.25 g m i = initial mass m f = final mass n = # of half lives

29. Detection of Radioactivity photographic film (film badges): cheap, “ballpark quantitative” Geiger counter: ionization of gas produces measurable electric current

30. Nuclear Fission Fission is when a BIG nucleus splits. This requires… neutrons! Important fissionable nuclei: U-233, U-235, Pu-239 chain reaction: one nuclear reaction leads to one or more others Anywhere from 1-9 n 0 are released! 1 0 n

31. Uranium consists mainly as U-238 (spent Uranium)

32. Chain Reaction

33. critical mass: (contained) the mass of fissionable material requiredto maintain a chain reaction at a constant rate. (Nuclear Reactor) safe critical mass (“Run, Forrest, run!”) supercritical mass supercritical mass: (uncontained) the mass above which the chain reaction accelerates (reaction maintained at constant rate) Little Boy, later dropped on Hiroshima (“Ah jes’ felt lahk runnING.”)

34. Nuclear Power Nuclear Power (controlled)

36. Nuclear Fusion (video)video When two small nuclei collide and “fuse” together to form one nucleus. This results in a LARGE amount of energy This happens at extreme temperatures…like the sun! The search for “cold fusion” is in progress.

38. Nuclear Fusion -- also called thermonuclear reactions -- products are generally NOT radioactive -- requires high temperatures (> 40,000,000 K) -- the tokamak uses magnetic fields to contain and heat the reaction !!!!