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Nuclear Reactions

Nuclear Reactions. Natural Transmutation. 1 term on reactant side Original isotope 2 terms on product side Emitted Particle New Isotope. Happens all by itself (spontaneous) Not affected by anything in environment. 8. -1. Natural Transmutation. 16 N  0 e + 16 O. 7.

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Nuclear Reactions

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  1. Nuclear Reactions

  2. Natural Transmutation • 1 term on reactant side • Original isotope • 2 terms on product side • Emitted Particle • New Isotope Happens all by itself (spontaneous) Not affected by anything in environment

  3. 8 -1 Natural Transmutation 16N 0e + 16O 7 2 terms on product side 1 term on reactant side

  4. Artificial Transmutation • Cause it to happen by smashing particles into one another • 2 terms on reactant side • Original Isotope • Particle that hits it • neutron, proton, or -particle • Product side: usually 2 terms

  5. 15 0 “Bullet” -what hits isotope Artificial Transmutation 27Al + 4He  30P + 1n 13 2 Original isotope or target nucleus

  6. 2 15 0 13 1 2 8 7 2 35 0 33 0 17 Artificial Transmutation 27Al + 4He 30P + 1n All of these equations have 2 reactants! 14N + 4He 17O + 1H 75As + 4He 78Br + 1n 37Cl + 1n 38Cl 17

  7. Bombarding with Protons or  • Protons and -particles have positive charge and mass • do some damage when hit target nucleus • must be accelerated to high speeds to overcome repulsive forces between nucleus & particle (both are +)

  8. What is an accelerator? • vacuum chamber (usually a long pipe) • surrounded by vacuum pumps, magnets, radio-frequency cavities, high voltage instruments and electronic circuits • inside the pipe particles are accelerated to very high speeds then smashed into each other

  9. Fission Reaction • Splitting heavy nucleus into 2 lighter nuclei • Requires a critical mass of fissionable isotope Controlled – nuclear reactor Uncontrolled – bomb

  10. Fission • Reactant side: 2 terms • 1 heavy isotope (examples: U-235 or Pu-239) • Bombarding particle – usually a neutron • Product side: at least 2 terms • 2 medium-weight isotopes • 1 or more neutrons • Huge amount of energy is released • Fission = Division

  11. 56 0 36 92 235U + 1n 72Zn + 160Sm + 41n + energy 30 0 92 Fission 235U + 1n 91Kr + 142Ba + 31n + energy 0 62 0 More than 200 different product isotopes identified from fission of U-235 A small amount of mass is converted to energy according to E = mc2

  12. Fission Chain Reaction

  13. 2 0 Fusion • Reactant side has 2 small nuclei: • H + H; H + He; He + He • Product side: • 1 nucleus (still small) and maybe a particle • Source of sun’s energy • 2 nuclei unite 2H + 3H 4He + 1n + energy 1 1

  14. CERN • 27 kilometer ring • Particles travel just below speed of light • In 10 hrs: particles make 400 million revolutions of the ring

  15. 4 miles in circumference! FermiLab

  16. Balancing Nuclear Equations

  17. Nuclear Equations - tasks • Identify type (4 types) • Balance to find 1 unknown term

  18. Natural Transmutation – ID • 1 term on reactant side • starting isotope • 2 terms on product side • ending isotope and emitted particle • Type of particle emitted characteristic of isotope – Table N

  19. Nuclear Equations • To balance: use conservation of both atomic number & mass number • Mass number = left superscript • Atomic Number = left subscript

  20. -1 7 8 Balancing Nuclear Equations 16N 0e + 16O Conservation of mass number: 16 = 0 + 16 Conservation of atomic number: 7 = -1 + 8

  21. Writing Equations • Write the equation for the decay of Thorium-232 • Use Table N to find the decay mode: α • Write the initial equation: 232Th 4He +X 90 2 figure out what element it turned into

  22. Write an equation for the α decay of Am-241 241Am 4He + YX What’s X? 95 2 Z

  23. so Y = 228 232 = 4 + Y Y Z 2 232Th 4He + X 90 Conservation of Mass Number: sum of mass numbers on left side must = sum of mass numbers on right side

  24. 90 2 Z 90 = 2 + Z so Z = 88 232Th 4He + 228X Conservation of Atomic Number: sum of atomic numbers on left side must = sum of atomic numbers on right side

  25. 2 90 88 X = Ra Use the PT to find X: 232Th 4He + 228Ra 90 2 88 232Th 4He + 228X

  26. Alpha (α) decay: 233U  229Th + 4He 92 90 2 232Th  228Ra + 4He 90 88 2 175Pt  171Os + 4He 78 76 2

  27. How does the mass number or atomic number change in α,β or γ decay? • go to Table N: • find isotope that decays by alpha or βdecay • write the equation • see how the mass number (or atomic number) changes • 22688Ra 42 + X so X has to be 22286X • X is Rn-222 • mass number decreases by 4; atomic number decreases by 2

  28. 241 = 4 + Y so Y = 237 241 Am 4He + YX Z 95 2 so Z = 93 95 = 2 + Z X = Np What’s X? Write an equation for the  decay of Am-241

  29. Radioactive Decay Series • Sometimes 1 transmutation isn’t enough to achieve stability • Some radioisotopes go through several changes before they achieve stability (and are no longer radioactive)

  30. β-14C 14N + 0e 6 7 -1 β+18F  18O + 0e 9 8 +1

  31. 86 88 How does the mass number or atomic number change in  or  decay? • Go to Table N; find an isotope that decays by α,  or , write the equation; see how the mass number (or atomic number) changes • 226Ra 4 + X so X has to be 222X • X is Ra-222 • mass number decreases by 4 • atomic number decreases by 2 2

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