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Nuclear Reactions

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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

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

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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

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Artificial Transmutation 27 Al + 4 He 30 P + 1 n 132 15 0 Original isotope or target nucleus “Bullet” -what hits isotope

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Artificial Transmutation 27 Al + 4 He 30 P + 1 n13 2150 14 N + 4 He 17 O + 1 H 7 28 1 75 As + 4 He 78 Br + 1 n 33 2350 37 Cl + 1 n 38 Cl 17 0 17 All of these equations have 2 reactants!

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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 +)

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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

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Fission Reaction S plitting heavy nucleus into 2 lighter nuclei S plitting heavy nucleus into 2 lighter nuclei Requires a critical mass of fissionable isotope Controlled – nuclear reactor Uncontrolled – bomb

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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

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Fission 235 U + 1 n 91 Kr + 142 Ba + 3 1 n + energy92036 560 235 U + 1 n 72 Zn + 160 Sm + 4 1 n + energy 92030062 More than 200 different product isotopes identified from fission of U-235 A small amount of mass is converted to energy according to E = mc 2

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Fission Chain Reaction

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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 2 H + 3 H 4 He + 1 n + energy 112 0

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

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FermiLab 4 miles in circumference!

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Balancing Nuclear Equations

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

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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

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

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

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Writing Equations Write the equation for the decay of Thorium-232 Use Table N to find the decay mode: α Write the initial equation: 232 Th 4 He + X figure out what element it turned into figure out what element it turned into 902

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Write an equation for the α decay of Am-241 241 Am 4 He + Y X What’s X? 952Z

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232 Th 4 He + X 902 Conservation of Mass Number: sum of mass numbers on left side must = sum of mass numbers on right side Y Z 232 = 4 + Y so Y = 228

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232 Th 4 He + 228 X902 Conservation of Atomic Number: sum of atomic numbers on left side must = sum of atomic numbers on right side Z 90 = 2 + Z so Z = 88

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

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

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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 β decay – write the equation – see how the mass number (or atomic number) changes 226 88 Ra 4 2 + X so X has to be 222 86 X X is Rn-222 – mass number decreases by 4; atomic number decreases by 2

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

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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)

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β- 14 C 14 N + 0 e β+ 18 F 18 O + 0 e 67 8 +19

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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 226 Ra 4 + X so X has to be 222 X X is Ra-222 – mass number decreases by 4 – atomic number decreases by 288286

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Fission and Fusion are both nuclear reactions that involve the particles in the nucleus of an atom.

Fission and Fusion are both nuclear reactions that involve the particles in the nucleus of an atom.

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