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power point for chapter 19

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  • 1. 1 Nuclear ChemistryNuclear Chemistry Chemistry I – Chapter 25Chemistry I – Chapter 25 Chemistry I Honors –Chemistry I Honors – Chapter 19Chapter 19 ICP – Chapter 18ICP – Chapter 18 SAVE PAPER AND INK!!! When you print out the notes on PowerPoint, print "Handouts" instead of "Slides" in the print setup. Also, turn off the backgrounds (Tools>Options>Print>UNcheck "Background Printing")!
  • 2. 2 RadioactivityRadioactivity • One of the pieces of evidence for theOne of the pieces of evidence for the fact that atoms are made of smallerfact that atoms are made of smaller particles came from the work ofparticles came from the work of ________________ (1876-1934).(1876-1934). • She discoveredShe discovered ________________, the, the spontaneous disintegration of somespontaneous disintegration of some elements into smaller pieces.elements into smaller pieces.
  • 3. 3 Nuclear Reactions vs.Nuclear Reactions vs. Normal Chemical ChangesNormal Chemical Changes • Nuclear reactions involve the nucleusNuclear reactions involve the nucleus • The nucleus opens, and protons andThe nucleus opens, and protons and neutrons are rearrangedneutrons are rearranged • The opening of the nucleus releases aThe opening of the nucleus releases a tremendous amount of energy that holdstremendous amount of energy that holds the nucleus together – calledthe nucleus together – called bindingbinding energyenergy • ““Normal” Chemical Reactions involveNormal” Chemical Reactions involve electronselectrons, not protons and neutrons, not protons and neutrons
  • 4. 4 Mass DefectMass Defect • Some of the mass can be converted intoSome of the mass can be converted into energyenergy • Shown by a very famous equation!Shown by a very famous equation! E=mcE=mc22 EnergyEnergy MassMass Speed of lightSpeed of light
  • 5. 5 Types of RadiationTypes of Radiation e0 1− He4 2 • Alpha (Alpha (άά) – a positively) – a positively charged helium isotopecharged helium isotope -- wewe usually ignore the charge because it involvesusually ignore the charge because it involves electrons, not protons and neutronselectrons, not protons and neutrons •Beta (Beta (ββ) – an electron) – an electron •Gamma (Gamma (γγ) – pure energy;) – pure energy; called a ray rather than acalled a ray rather than a particleparticle γ0 0
  • 6. 6 Other Nuclear ParticlesOther Nuclear Particles e0 1+ n1 0• NeutronNeutron • Positron – a positivePositron – a positive electronelectron •Proton – usually referred toProton – usually referred to as hydrogen-1as hydrogen-1 •Any other elemental isotopeAny other elemental isotope H1 1
  • 7. 7 Penetrating AbilityPenetrating Ability
  • 8. 8 Balancing Nuclear ReactionsBalancing Nuclear Reactions •In the reactants (starting materials – on the left side of an equation) and products (final products – on the right side of an equation) Atomic numbers must balance and Mass numbers must balance •Use a particle or isotope to fill in the missing protons and neutrons
  • 9. 9 Nuclear ReactionsNuclear Reactions • Alpha emissionAlpha emission Note that mass number (A) goes down by 4 and atomic number (Z) goes down by 2. Nucleons (nuclear particles… protons and neutrons) are rearranged but conserved
  • 10. 10 Nuclear ReactionsNuclear Reactions • Beta emissionBeta emission Note that mass number (A) is unchanged and atomic number (Z) goes up by 1.
  • 11. 11 Other Types of Nuclear ReactionsOther Types of Nuclear Reactions Positron (Positron (00 +1+1ββ): a positive electron): a positive electron Electron capture:Electron capture: the capture of an electron 207 207
  • 12. 12 Learning Check What radioactive isotope is produced in the following bombardment of boron? 10 B + 4 He ? + 1 n 5 2 0
  • 13. 13 Write Nuclear Equations! Write the nuclear equation for the beta emitter Co-60.
  • 14. 14 Artificial Nuclear ReactionsArtificial Nuclear Reactions New elements or new isotopes of known elementsNew elements or new isotopes of known elements are produced by bombarding an atom with aare produced by bombarding an atom with a subatomic particle such as a proton or neutronsubatomic particle such as a proton or neutron -- or even a much heavier particle such as-- or even a much heavier particle such as 44 HeHe andand 1111 B.B. Reactions using neutrons are calledReactions using neutrons are called γγ reactionsreactions because abecause a γγ ray is usuallyray is usually emitted.emitted. Radioisotopes used in medicine are often made byRadioisotopes used in medicine are often made by γγ reactions.reactions.
  • 15. 15 Artificial Nuclear ReactionsArtificial Nuclear Reactions Example of aExample of a γγ reactionreaction is productionis production of radioactiveof radioactive 3131 P for use in studies of PP for use in studies of P uptake in the body.uptake in the body. 3131 1515P +P + 11 00n --->n ---> 3232 1515P +P + γγ
  • 16. 16 Transuranium ElementsTransuranium Elements Elements beyond 92Elements beyond 92 (transuranium)(transuranium) mademade starting with anstarting with an γγ reactionreaction 238238 9292U +U + 11 00n --->n ---> 239239 9292U +U + γγ 239239 9292UU --->---> 239239 9393Np +Np + 00 -1-1ββ 239239 9393NpNp --->---> 239239 9494Pu +Pu + 00 -1-1ββ
  • 17. 17 Nuclear FissionNuclear Fission
  • 18. 18 Nuclear FissionNuclear Fission Fission is the splitting of atomsFission is the splitting of atoms These are usually very large, so that they are not as stableThese are usually very large, so that they are not as stable Fission chain has three general steps:Fission chain has three general steps: 1.1. Initiation.Initiation. Reaction of a single atom starts theReaction of a single atom starts the chain (e.g.,chain (e.g., 235235 U + neutron)U + neutron) 2.2. PropagationPropagation.. 236236 U fission releases neutrons thatU fission releases neutrons that initiate other fissionsinitiate other fissions 3.3. ______________________ ..
  • 19. 19 StabilityStability of Nucleiof Nuclei • Out of > 300 stable isotopes: EvenEven OddOdd OddOdd EvenEven ZZ NN 157157 5252 5050 55 3131 1515PP 1919 99FF 22 11H,H, 66 33Li,Li, 1010 55B,B, 1414 77N,N, 180180 7373TaTa
  • 20. 20 Band of StabilityBand of Stability and Radioactiveand Radioactive DecayDecay
  • 21. 21 Representation of a fission process.
  • 22. 22 Nuclear Fission & POWERNuclear Fission & POWER • Currently about 103Currently about 103 nuclear power plants innuclear power plants in the U.S. and about 435the U.S. and about 435 worldwide.worldwide. • 17% of the world’s17% of the world’s energy comes fromenergy comes from nuclear.nuclear.
  • 23. 23 Figure 19.6: Diagram of a nuclear power plant.
  • 24. 24 Nuclear Fusion Fusion small nuclei combine 2 H + 3 H 4 He + 1 n + 1 1 2 0 Occurs in the sun and other stars Energy
  • 25. 25 Nuclear Fusion Fusion • Excessive heat can not be contained • Attempts at “cold” fusion have FAILED. • “Hot” fusion is difficult to contain
  • 26. 26 Half-LifeHalf-Life • HALF-LIFEHALF-LIFE is the time that it takes foris the time that it takes for 1/2 a sample to decompose.1/2 a sample to decompose. • The rate of a nuclear transformationThe rate of a nuclear transformation depends only on the “reactant”depends only on the “reactant” concentration.concentration.
  • 27. 27 Half-LifeHalf-Life Decay of 20.0 mg ofDecay of 20.0 mg of 1515 O. What remains after 3 half-lives?O. What remains after 3 half-lives? After 5 half-lives?After 5 half-lives?
  • 28. 28 Kinetics of Radioactive DecayKinetics of Radioactive Decay For each duration (half-life), one half of the substance decomposes. For example: Ra-234 has a half-life of 3.6 days If you start with 50 grams of Ra-234 After 3.6 days > 25 gramsAfter 3.6 days > 25 grams After 7.2 days > 12.5 gramsAfter 7.2 days > 12.5 grams After 10.8 days > 6.25 gramsAfter 10.8 days > 6.25 grams
  • 29. 29 Learning Check! The half life of I-123 is 13 hr. How much of a 64 mg sample of I-123 is left after 39 hours?
  • 30. 30 Effects of RadiationEffects of Radiation
  • 31. 31 Geiger Counter • Used to detect radioactive substances
  • 32. 32
  • 33. 33 Radiocarbon DatingRadiocarbon Dating Radioactive C-14 is formed in the upper atmosphereRadioactive C-14 is formed in the upper atmosphere by nuclear reactions initiated by neutrons inby nuclear reactions initiated by neutrons in cosmic radiationcosmic radiation 1414 N +N + 11 oon --->n ---> 1414 C +C + 11 HH The C-14 is oxidized to COThe C-14 is oxidized to CO22, which circulates, which circulates through the biosphere.through the biosphere. When a plant dies, the C-14 is not replenished.When a plant dies, the C-14 is not replenished. But the C-14 continues to decay with tBut the C-14 continues to decay with t1/21/2 = 5730= 5730 years.years. Activity of a sample can be used to date the sample.Activity of a sample can be used to date the sample.
  • 34. 34 Nuclear Medicine: ImagingNuclear Medicine: Imaging Thyroid imaging using Tc-99mThyroid imaging using Tc-99m
  • 35. 35 Food IrradiationFood Irradiation •Food can be irradiated withFood can be irradiated with γγ rays fromrays from 6060 Co orCo or 137137 Cs.Cs. •Irradiated milk has a shelf life of 3 mo.Irradiated milk has a shelf life of 3 mo. without refrigeration.without refrigeration. •USDA has approved irradiation of meatsUSDA has approved irradiation of meats and eggs.and eggs.

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