1. Chapter 22 Nuclear Reactions

2. Nuclear Rxns Nuclear reaction-a reaction that involves a change in an atom’s nucleus. Therefore, an atom of one element changes into an atom of another element.

3. Nuclear Rxns Nuclide (Nucleus of an atom) Contains nucleons(protons and neutrons)

4. Chemical vs. Nuclear Rxns. Associated with large energy changes Associated with small energy changes May involve p, n Involve only outer electrons Atoms are often converted into atoms of another element. Atoms remain unchanged, just rearranges Occur when nuclei emit particles and/or rays Occur when bonds are broken and formed Nuclear RxnsChemical Rxns

5. Radiation Radiation-The rays and particles that are emitted by radioactive materials.

6. Alpha Radiation Alpha radiation-radiation deflected towards the negatively charged plate and gives off alpha particles Alpha particles, He or α : 2p, 2n so +2 charge, largest mass (4 amu)

7. Beta Radiation Beta radiation-radiation deflected towards the positively charged plate and gives off beta particles (electrons). Beta particles, β or e: 1e so -1 charge, mass is between alpha and gamma particles

8. Gamma Radiation Gamma radiation-radiation deflected towards no plate and gives off gamma rays Gamma rays, γ : no mass and no charge, usually occupied by α and β decay.

9. Nuclear Rxns (1) Ra → Rn + He α decay (2) C → N + e β decay (3) U → Th + He + 2γ γ decay

10. Types of Radiation (Memorize) Consists Charge Mass Stopped w/ symbol Alpha Beta Gamma

11. Types of Radiation Positron emission-radioactive decay that involves the emission of a positron from a nucleus (antimatter) Positron-particle with the same mass as the electron but opposite charge Symbol:

12. Types of Radiation Electron Capture- nucleus of an atom draws in a surrounding electron and an X-ray photon is emitted Symbol:

13. Nuclear Reactions Nuclear Rxn- a rxn that changes the nucleus Transmutation-a change in the identity of the nucleus, change in # of protons in nucleus.

14. Nuclear Stability Mass defect – diff. between mass of an atom and sum of masses for p, n, e. Why loss of mass? Caused by conversion of mass to energy upon formation of nucleus

15. Nuclear Binding energy – energy released upon formation of nucleus

16. Nuclear Stability The smaller stable nuclides have a neutron-proton of 1:1 to the larger nuclides of 1.5:1. If the nuclei ratio falls above/below the band of stability, the nuclides will undergo decay until they are within the band of stability.

17. Radioactive decay Radioactive decay-spontaneous disintegration of an unstable nucleus to a smaller nucleus by giving off nuclear radiation. Radioactive nuclide- unstable nucleus that will undergo radioactive decay

18. Nuclear Rxns Identify the product that balances the following nuclear rxns. 1. 212 Po → 4 He + ____ 2. 230 Th → _____ + 4 He 3. 238 U + 4 He → ____ + 1 n 4. 27 Al + 1 n → 24 Na + ____

19. Radioactive decay Alpha Emission 210 Po  206 Pb + ____ Beta Emission 14 C  14 N + ____ Electron Capture (reverse of beta) 106 Ag + _____  106 Pd Positron emission 11 C → 11 B + _____

20. Half-life Half-Life- t 1/2 - the time required for half the atoms of a radioactive element to decay into another element. Fluorine-21 has a half life,t 1/2, of 5 seconds 1000 atoms F-21500 atoms F-21  250 atoms F-21 1(whole amt)  ½ left  ¼ left 100 g F-21 50 g F-2125 g F-21

21. Half-Life Problems Formulas: To determine the number of half-lives that past: #half-lives past = total time t 1/2 To determine amount remaining: Amount remaining = (Initial amt)1 n 2 n= # of half lives past

22. Half-Life Problems 1. If the radioactive sample of I-131 was 18.5g, what amt is left after 32 days? (t 1/2 = 8 days)

23. Half-Life Problems 2.Iron-59 is used in medicine to diagnosis blood circulation disorders. The half-life of iron-59 is 44.5 days. How much of a 2.000 mg sample will remain after 133.5 days?

24. Half-Life Problems 3. If gallium-68 has a half-life of 68.3 minutes, how much of a 10.0 mg sample is left after two half-lives?

25. Half-Life 4. After 15 days only 2 grams remain of a sample that has a half life of 5 days. How many grams were in the original amount? 5. What is the half life of K-42 if a 750 gram sample decays to 93.75 grams in 24 hours?

26. 6. The half-life of carbon-14 is 5715 years. A sample has only ¼ of its original amount. What is the age of the sample?

27. Decay Series Decay Series-a series of radioactive nuclides produced by successive radioactive decay until a stable nuclide is reached

28. Decay Series Questions Use pg. 814 Write the four nuclear equations of the uranium-238 decay series. What stable nuclide does U-238 finally become? How long is the half life of U-238?

29. U-238 U-238 is found in small amounts in soil and rock, particularly, shale and granite. Rn is one of the daughter nuclide of U- 238(parent nuclide) decay. Rn is a radioactive gas that can be a health hazard trapped in homes from cracks and holes in foundation. It can cause lung cancer and birth defects. Ra-226, Po-210, Pb-210 are found in cigarettes and the lungs of smokers.

30. Induced Transmutation Induced Transmutation- bombardment of stable nuclei with charged and uncharged particles. This process is used to make radioactive nuclides not found nature, like our newly discovered elements.

31. Induced Transmutation 1. Write a balanced nuclear equation for the induced transmutation of aluminum- 27 into phosphorus-30 by alpha particle bombardment. A neutron is emitted from the aluminum atom.

32. Induced Transmutation 2. Write the balanced nuclear equation for the induced transmutation of aluminum-27 into sodium-24 by neutron bombardment. An alpha particle is released in the rxn.

33. Induced Transmutation What element would be formed in the following nuclear rxn? 3. 242 Cm + 4 He  ______ + 1 n

34. Nuclear Radiation Radiation Exposure Rem-a unit used to measure radiation damage to human tissue like x-rays… (Complete personal radiation wkst)

35. Nuclear Radiation Radiation Detection Geiger Muller counters -measures electrical pulses on gas ionized by radiation Film badges Scintillation counter

36. Geiger Counter

37. Applications of Nuclear Radiation Radiochemical Dating: 14 C  0 e + 14 N t 1/2 = 5715 yrs Living organisms absorb 14 C through food. This C-14 is a constant amt. When the organism dies, there is no new absorption of C-14. The C-14 decays to N-14. By measuring the amount of C- 14 the age may be approximated.

38. Applications of Nuclear Radiation Radioactive Nuclides in Medicine Radioactive tracers are radioactive atoms incorporated into substances so they can be followed by radiation detectors. Ex. Tc-99 used to detect bone cancer, I-131 to detect thyroid problems

39. Applications of Nuclear Radiation Radioactive Nuclides in Agriculture Radioactive tracers are used to determine effectiveness of fertilizers. Cobalt-60 is used to irradiate food, to kill bacteria and insects. It is also used to kill cancer cells.

40. Nuclear Waste 1. Produced from nuclear power plants, nuclear weapons manufacturing, medical research,… 2. Containment on nuclear waste from nuclear power plants is on-site and off-site disposal.

41. Nuclear Waste *3. Each nuclear reactor has large pools of water where spent uranium fuel rods can be stored. 4. When the pools are filled, they are sealed in concrete and steel dry casks then moved to permanent storage facilities. There are 77 disposal sites in the US.

42. Nuclear Fission

43. Nuclear Fission- splitting a larger nucleus to smaller intermediate nuclides Nuclear Reactors use controlled fission reactions to produced energy by this rxn:

44. Parts of Nuclear Reactor Chain rxn-self propagating rxn Fuel- U-235 Moderator-slows down high speed neutrons to CONTINUE chain rxn; uses water, Be, or C(graphite) Control Rods -absorbs neutrons, thereby controlling rate of fission rxn; made of Cd

45. Parts of Nuclear Reactor Coolant-water to remove heat to turbines to generate electricity Containment structure(shielding)- structure built around reactor to hold in radiation from escaping in case of an accident; server feet thick concrete.

47. Recent Nuclear Accidents 1986 Chernobyl power plant in Soviet Union-Complete meltdown of core 1979 Three Mile Island, USA- partial meltdown

48. Nuclear Fusion Nuclear Fusion-small nuclei join to form larger nuclei Ex. sun and stars fusion releases 20X more energy per gram than fission Uses: hydrogen bomb and in future fusion power plants

49. Fusion Reactors Disadvantages of fusion reactors Huge input of energy needed to start process A temperature of 200 million K needed to sustain rxn.

50. Fusion Reactors Advantages of fusion reactors: Readily available hydrogen from water Nonradioactive products Can stop rxn by dropping temp. Can produce inexhaustible supply of energy