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Powerpoint Chapter 22

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  • 1. New Title Page Chapter 21:Nuclear Chemistry Date start: 1-19-2010 Date Finished: Your Name Period Mr. Costein
  • 2. Chapter21: NuclearChemistryChapter21: NuclearChemistry This unit looks at the nature of radiation, Types of radiation and decay products, Radiation Units and exposure precautions Nuclear fission and fusion reactions Applications of Nuclear Chemistry
  • 3. The Geiger Counter
  • 4. What does a Geiger Counter measure? Radiation that can cause atoms to lose or gain electrons and become ionsions. This type of radiation is called ionizing radiation. There are two causes of background radiation: Outer Space- Cosmic rays Natural decay from isotopes in the earth’s crust/core
  • 5. Daily Background Counts DateDate Trial 1Trial 1 Trial 2Trial 2 AverageAverage FinalFinal CPMCPM
  • 6. Historical Perspectives 1895: WilhelmRoentgen discovers X-rays and their1895: WilhelmRoentgen discovers X-rays and their effects.effects. 1896: Henri Becquerel discovers radioactive Uranium.1896: Henri Becquerel discovers radioactive Uranium. 1898: Pierre and Marie Curie discovertwo new elements,1898: Pierre and Marie Curie discovertwo new elements, poloniumand radium.poloniumand radium. 1905: Albert Einstein theory of relativity and mass1905: Albert Einstein theory of relativity and mass defect.defect. 1908: Hans Geigercreates an instrument to measure1908: Hans Geigercreates an instrument to measure ionizing radiation.ionizing radiation. 1934: Enrico Fermi proposes ‘transuranes” elements1934: Enrico Fermi proposes ‘transuranes” elements beyond uranium.beyond uranium. 1939: Lise Meitner, Otto Hahn and Fritz Stassman1939: Lise Meitner, Otto Hahn and Fritz Stassman explain nuclearfission.explain nuclearfission.
  • 7. Nuclear Composition Nucleons are any particles found in the nucleus,Nucleons are any particles found in the nucleus, commonly they are protons and neutrons.commonly they are protons and neutrons. We would expect, the total mass of the electrons,We would expect, the total mass of the electrons, protons, and neutrons would be the mass of theprotons, and neutrons would be the mass of the atom, it is not, but ratherit is a smallervalue.atom, it is not, but ratherit is a smallervalue. Mass defectMass defect is the difference between the mass of anis the difference between the mass of an atom and the sum of the masses of its protons,atom and the sum of the masses of its protons, neutrons and electrons.neutrons and electrons. Einstein explained this loss of mass as the result ofEinstein explained this loss of mass as the result of the nucleus formation. Energy is given off from thethe nucleus formation. Energy is given off from the conversion of matterto energy (E=mcconversion of matterto energy (E=mc22 ).). This loss of mass from it’s conversion to energyThis loss of mass from it’s conversion to energy provides nuclearstability.provides nuclearstability.
  • 8. NuclearBinding EnergyNuclearBinding Energy The energy released when a nucleus is formed fromThe energy released when a nucleus is formed from nucleons is called thenucleons is called the nuclearbinding energynuclearbinding energy.. This can be thought of the amount of energy toThis can be thought of the amount of energy to breaka nucleus apart.breaka nucleus apart. The higherthe nuclearbinding energy of a nuclide.The higherthe nuclearbinding energy of a nuclide. the greaterthe nuclide stability.the greaterthe nuclide stability. TheThe binding energy pernucleonbinding energy pernucleon is the binding energyis the binding energy of the nucleus divided by the numberofof the nucleus divided by the numberof nucleons(mass number) it contains.nucleons(mass number) it contains. Elements with intermediate atomic masses (ironElements with intermediate atomic masses (iron through lead) have the greatest binding energiesthrough lead) have the greatest binding energies (stability).(stability).
  • 9. Nuclear Binding Example Problem 4 He 2 2 protons = 2 x 1.007276 = 2.014 552 amu 2 neutrons = 2 x 1.008665 = 2.017 330 amu 2 electrons = 2 x 0.0005486 = 0.001 097 amu Total mass combined = 4.032 979 amu Measured mass = 4.002 602 amu Mass Defect = 4.032979 – 4.002602 = 0.030377 amu
  • 10. Nuclear Binding Page 2 Mass Defect = 4.032979 – 4.002602 = 0.030377 amu To convert amu to kg: 1 amu = 1.6605 x 10-27 kg 0.030377amu X 1.6605 x 10-27 kg = 5.0441 x 10-29 kg 1 amu Binding Energy = E = mc2
  • 11. Nuclear Binding Page 3 Binding Energy = E = mcBinding Energy = E = mc22 Mass= 5.0441 x 10-29 kg c = speed of light = 3.00 x 108 m/s So E = (5.0441 x 10-29 kg)(3.00 x 108 m/s)2 E = 4.54 x 10-12 Jperatom E = 6.022 x 1023 atoms/mol * 4.54 x 10-12 Jperatom E= 2.733988 x 1012 J/mol (4 g of helium)
  • 12. NuclearStabilityNuclearStability The neutron/proton ratio can be used to predictThe neutron/proton ratio can be used to predict nuclearstability.nuclearstability. Forelements with low atomic numbers (1-30)Forelements with low atomic numbers (1-30) the nucleus is stable when there is a 1:1 ratio.the nucleus is stable when there is a 1:1 ratio. Forelements with a high atomic number(up toForelements with a high atomic number(up to element 83), the nucleus is stable when the ratioelement 83), the nucleus is stable when the ratio is 1.5:1.is 1.5:1. Elements having an atomic numbergreaterthanElements having an atomic numbergreaterthan 83 are unstable orradioactive.83 are unstable orradioactive. Stable nuclei tend to have even numbers ofStable nuclei tend to have even numbers of nucleons in theirnucleus.nucleons in theirnucleus.
  • 13. N/PRatioN/PRatio
  • 14. NuclearShell ModelNuclearShell Model Stable nuclei tend to have even numbers ofStable nuclei tend to have even numbers of nucleons in theirnucleus. (protons, neutrons ornucleons in theirnucleus. (protons, neutrons or total nucleons)total nucleons) The most stable atoms have 2, 8, 20, 28, 50, 82 orThe most stable atoms have 2, 8, 20, 28, 50, 82 or 126 protons, neutrons, ortotal nucleons.126 protons, neutrons, ortotal nucleons. The nuclearshell theory states that nucleons existsThe nuclearshell theory states that nucleons exists in different energy levels, orshells, in the nucleus.in different energy levels, orshells, in the nucleus. Completed nuclearenergy levels are those with 2, 8,Completed nuclearenergy levels are those with 2, 8, 20, 28, 50, 82 and 126 nucleons.20, 28, 50, 82 and 126 nucleons. These numbers are sometimes called the “These numbers are sometimes called the “magicmagic numbers”numbers”fornuclearstability.fornuclearstability. If both the protons and neutrons are equal to theIf both the protons and neutrons are equal to the magic numbers, these are called the “magic numbers, these are called the “double magicdouble magic numbersnumbers” and have the greatest stability.” and have the greatest stability.
  • 15. NuclearShell Model ExamplesNuclearShell Model Examples The most stable atoms have 2, 8, 20, 28, 50,The most stable atoms have 2, 8, 20, 28, 50, 82 or126 protons, neutrons, ortotal82 or126 protons, neutrons, ortotal nucleons.nucleons. Examples of stable nuclidesExamples of stable nuclides 4040 CaCa 2020 1616 OO 88 2828 SiSi 1414
  • 16. NuclearReactions and terms:NuclearReactions and terms: 4 types of NuclearReactions:4 types of NuclearReactions: Radioactive decayRadioactive decay refers to the emission of an alpharefers to the emission of an alpha particle, a beta particle, orgamma ray and theparticle, a beta particle, orgamma ray and the formationof aslightlylighterandmorestablenucleusformationof aslightlylighterandmorestablenucleus.. NucleardisintegrationNucleardisintegration is when an unstable nucleiis when an unstable nuclei fromnuclearbombardmentfromnuclearbombardment emits aprotonorneutronemits aprotonorneutron and becomes more stable.and becomes more stable. FissionFission refers to the process in which a veryrefers to the process in which a very heavyheavy nucleus splitsnucleus splits to formtwo ormore medium-massto formtwo ormore medium-mass nuclei.nuclei. FusionFusion refers to the process in which lightweightrefers to the process in which lightweight nucleicombinenucleicombine to formheaviermore stable nuclei.to formheaviermore stable nuclei.
  • 17. OtherNuclearTerms:OtherNuclearTerms: TransmutationTransmutation is the changeis the change in the identity of ain the identity of a nucleus as a result of a change in the numberof protons.nucleus as a result of a change in the numberof protons. Radioactive decayRadioactive decay is spontaneous disintegration ofis spontaneous disintegration of a nucleus into slightly lighterand more stable nucleus,a nucleus into slightly lighterand more stable nucleus, accompanied by the emission of particles,accompanied by the emission of particles, electromagnetic radiation orboth.electromagnetic radiation orboth. RadiationRadiation- the process of emitting orreleasing waves- the process of emitting orreleasing waves of energy, such as light, x-rays, orothertypes ofof energy, such as light, x-rays, orothertypes of electromagnetic waves.electromagnetic waves. RadioactivityRadioactivity is the property of some elements tois the property of some elements to spontaneously emit alpha orbeta particles with gammaspontaneously emit alpha orbeta particles with gamma rays by the disintegration of the nuclei.rays by the disintegration of the nuclei.
  • 18. Properties of Radioactive Nuclides:Properties of Radioactive Nuclides: They expose light sensitive emulsions.They expose light sensitive emulsions. (Roentgen, 1895)(Roentgen, 1895) They fluoresce orglow with certain compounds.They fluoresce orglow with certain compounds. (Curie, 1898)(Curie, 1898) They produce “charged” orionized gas particles.They produce “charged” orionized gas particles. (Geiger, 1908)(Geiger, 1908) Exposure to radio-nuclides can cause harmfulExposure to radio-nuclides can cause harmful physiological effects leading to death.physiological effects leading to death. They undergo radioactive decay and have a half-life.They undergo radioactive decay and have a half-life.
  • 19. Half-Life of a Radioisotope Half-lifeHalf-life is the time it required forhalf the atoms ofis the time it required forhalf the atoms of a radioactive nuclide to decay. It can be measured ina radioactive nuclide to decay. It can be measured in seconds, minutes, days, oryears.seconds, minutes, days, oryears. decay curve 8 mg 4 mg 2 mg 1 mg initial 1 half-life 2 3
  • 20. Examples of Half-Life IsotopeIsotope Half lifeHalf life C-15C-15 2.4 sec2.4 sec K-42K-42 12.36 hours12.36 hours Na-24Na-24 15 hours15 hours Ra-224Ra-224 3.6 days3.6 days Ra-223Ra-223 12 days12 days I-125I-125 60 days60 days C-14C-14 5700 years5700 years U-235U-235 710 000 000 years710 000 000 years
  • 21. Half-Life Problem Ra-223 has a half-life of 12 days. If today,Ra-223 has a half-life of 12 days. If today, you had 100 grams of this isotope, howyou had 100 grams of this isotope, how much would remain after36 days?much would remain after36 days? 1.1. How many half-life periods has it undergone in 36 days?How many half-life periods has it undergone in 36 days? 36 days36 days = 3 half life periods= 3 half life periods 12 days/half-life12 days/half-life 100 g 50g 25g 12.5 g
  • 22. Types of Radioactive DecayTypes of Radioactive Decay Alpha EmissionAlpha Emission Beta EmissionBeta Emission Positron EmissionPositron Emission Electron CaptureElectron Capture Gamma EmissionGamma Emission
  • 23. Comparing Nuclide EmissionsComparing Nuclide Emissions
  • 24. Decay Models Graphic shows U-238 with an alpha and one beta decays.Graphic shows U-238 with an alpha and one beta decays. Protactinium atomic number 91 is formed.Protactinium atomic number 91 is formed.
  • 25. Alpha and Beta DecayAlpha and Beta Decay Alpha decayAlpha decay Beta DecayBeta Decay
  • 26. Key points in Balancing Nuclear Equations 1. Most decay products reduce the decaying atom’s atomic mass or atomic number or both. 2. The beta particle is the exception, when it is a decay product, the atomic number of the decaying atom increases by one. 3. Gamma ray emission by a decaying atom does NOT change the atomic mass or atomic number of the atom.
  • 27. Nuclear Equation Problem
  • 28. Example Nuclear Reactions 226 Ra 226 Ac + ________ 88 89 226 Pu 4 He + ________ 94 2 235 U 235 Pa + ________ 92 91
  • 29. Alpha EmissionAlpha Emission consists of a Helium nucleus with no electrons.consists of a Helium nucleus with no electrons. has 2 protons and 2 neutrons.has 2 protons and 2 neutrons. has a +2 chargehas a +2 charge has an atomic mass of 4has an atomic mass of 4 has a speed that is 1/10 the speed of light.has a speed that is 1/10 the speed of light. can be stopped by a piece of paper, cloth, orcan be stopped by a piece of paper, cloth, or skin.skin. The symbol is the GreekletteralphaThe symbol is the Greekletteralpha αα particle orparticle or 44 22 HeHe
  • 30. Beta EmissionBeta Emission is a stream of negatively charged electrons.is a stream of negatively charged electrons. has a very light mass of an electronhas a very light mass of an electron has a -1 chargehas a -1 charge can be stopped by a piece of aluminumcan be stopped by a piece of aluminum has a speed that is 90% of the speed of light.has a speed that is 90% of the speed of light. can ionize airand otherparticles.can ionize airand otherparticles. The symbol is the Greekletter, betaThe symbol is the Greekletter, beta ββ−− particle orparticle or 00 -1-1 ee
  • 31. Positron EmissionPositron Emission is a stream of positively charged electrons.is a stream of positively charged electrons. has a very light mass of an electronhas a very light mass of an electron has a +1 chargehas a +1 charge (change this in notes)(change this in notes) can be stopped by a piece of aluminumcan be stopped by a piece of aluminum has a speed that is 90% of the speed of light.has a speed that is 90% of the speed of light. can ionize airand otherparticles.can ionize airand otherparticles. The symbol is the Greekletter, betaThe symbol is the Greekletter, beta ββ++ particle or oparticle or o +1+1 ee
  • 32. Electron CaptureElectron Capture is a capture of an innerorbital electron byis a capture of an innerorbital electron by the nucleus.the nucleus. has a very light mass of an electron.has a very light mass of an electron. has a -1 charge.has a -1 charge. results in a combination of an electron and aresults in a combination of an electron and a proton to forma neutron.proton to forma neutron. The symbol on the reaction side of a nuclearThe symbol on the reaction side of a nuclear reaction is oreaction is o -1-1 ee
  • 33. Gamma EmissionGamma Emission is formof energy orelectromagnetic radiation.is formof energy orelectromagnetic radiation. has an extremely short wavelength.has an extremely short wavelength. has no mass since it is energy.has no mass since it is energy. travel at the speed of light.travel at the speed of light. can cause airand most materials to become ionizedcan cause airand most materials to become ionized orcharged.orcharged. can only be stopped by using 2 to 4 inches of lead orcan only be stopped by using 2 to 4 inches of lead or many feet of concrete.many feet of concrete. does not change the identity of the radionuclide.does not change the identity of the radionuclide. The symbol is the Greekletter, gammaThe symbol is the Greekletter, gamma γγ
  • 34. Decay SeriesDecay Series AA decay seriesdecay series is a series of radioactiveis a series of radioactive nuclides produced by successive radioactivenuclides produced by successive radioactive decay until a stable nuclide is reached.decay until a stable nuclide is reached. The heaviest nuclide in a decay series isThe heaviest nuclide in a decay series is called thecalled the parent nuclideparent nuclide.. The particles in a decay series that areThe particles in a decay series that are produced fromparent nuclides are calledproduced fromparent nuclides are called daughternuclidesdaughternuclides.. U-238 the parent nuclide decays to Pb-206,U-238 the parent nuclide decays to Pb-206, which is stable and non-radioactive.which is stable and non-radioactive.
  • 35. U-238 Decay SeriesU-238 Decay Series
  • 36. Units of Radioactivity:Units of Radioactivity: Roentgen:Roentgen: the amount of gamma orx-raysthe amount of gamma orx-rays required to produce one unit of electricalrequired to produce one unit of electrical charge percubic centimeterfromcharge percubic centimeterfrom ionization of air. (1 roentgen = 86 ergs perionization of air. (1 roentgen = 86 ergs per gram)gram) REP:REP: (roentgen equivalent units) the(roentgen equivalent units) the amount of radiation to produce an harmfulamount of radiation to produce an harmful effect on living tissue.effect on living tissue. REM:REM: (roentgen equivalent man) the(roentgen equivalent man) the amount of radiation that produces theamount of radiation that produces the same biological damage in man resultingsame biological damage in man resulting from the absorption of 1 REPof radiation.from the absorption of 1 REPof radiation.
  • 37. Additional Units ofAdditional Units of RadioactivityRadioactivity Curie:Curie: the numberof nucleardisintegrationsthe numberof nucleardisintegrations that occurin one second. Commonly used inthat occurin one second. Commonly used in medical laboratory diagnostic procedures.medical laboratory diagnostic procedures. One cure is 3.7 x 10One cure is 3.7 x 101010 nucleardisintegrations.nucleardisintegrations. RAD:RAD: (radiation absorbed dose) similarto a(radiation absorbed dose) similarto a REM, and is used in monitoring dosimeterREM, and is used in monitoring dosimeter measurements forX-ray personnel.measurements forX-ray personnel. Sievert(Sv)- SI derived unit of dose and reflectsSievert(Sv)- SI derived unit of dose and reflects the biological effects of radiation that isthe biological effects of radiation that is absorbed (in gray units).absorbed (in gray units). REMS, and RADS are the two most commonREMS, and RADS are the two most common units formeasuring radiation exposure.units formeasuring radiation exposure.
  • 38. Exposure Limits:Exposure Limits: Average citizen:Average citizen: No more than 500 millirems peryear.No more than 500 millirems peryear. X-rays can cause exposures of 100 milliremperX-rays can cause exposures of 100 milliremper procedure.procedure. Radiation orNuclearmedicine workers:Radiation orNuclearmedicine workers: No more than 5 rems peryear.No more than 5 rems peryear. Physiological effects:Physiological effects: Acute Radiation sickness: 100-400 remsAcute Radiation sickness: 100-400 rems LD-50 (lethal dose 50%):LD-50 (lethal dose 50%): 400 rems400 rems LD-100 Death:LD-100 Death: over1000 remsover1000 rems Hyperlink to Radiation poisoning
  • 39. Protection fromRadiationProtection fromRadiation Three factors to protect radiationThree factors to protect radiation workers areworkers are S-S-ShieldingShielding;; the use of lead and orthe use of lead and or concrete in highconcrete in high radiation areas.radiation areas. T-T-TimeTime;; limit the amount oflimit the amount of time in hightime in high radiation areas.radiation areas. D-D-DistanceDistance;; the fartheraway fromthe fartheraway from a high radiation areaa high radiation area the lowerthe exposure.the lowerthe exposure.
  • 40. Shielding GraphicShielding Graphic
  • 41. NuclearFissionNuclearFission When a nucleus fissions, it splits into several smallerWhen a nucleus fissions, it splits into several smaller fragments oratoms.fragments oratoms. These fragments, orfission products, are about equal toThese fragments, orfission products, are about equal to half the original mass.half the original mass. Two orthree neutrons can also be emitted.Two orthree neutrons can also be emitted. The sumof the masses of these fragments is less thanThe sumof the masses of these fragments is less than the original mass. This 'missing' mass (about 0.1 percentthe original mass. This 'missing' mass (about 0.1 percent of the original mass) has been converted into energyof the original mass) has been converted into energy according to Einstein's equation.according to Einstein's equation. Fission can occurwhen a nucleus of a heavy atomFission can occurwhen a nucleus of a heavy atom captures a neutron, orit can happen spontaneouslycaptures a neutron, orit can happen spontaneously
  • 42. Fission ReactorsFission Reactors The heat froma fission reactoris used to heatThe heat froma fission reactoris used to heat waterto steam, which turns turbines to generatewaterto steam, which turns turbines to generate electricity.electricity. Fuels rods made of aluminumhold theFuels rods made of aluminumhold the Uranium-235 orU-238 which is the most commonUranium-235 orU-238 which is the most common nuclide used in fission reactors.nuclide used in fission reactors. Control rods made of neutron-absorbing steel areControl rods made of neutron-absorbing steel are used to limit the numberof free neutrons.used to limit the numberof free neutrons. Graphite(carbon) is used to slow down fastGraphite(carbon) is used to slow down fast neutrons produced fromfission.neutrons produced fromfission. Control rods allow fora limited self-sustainingControl rods allow fora limited self-sustaining reaction.reaction.
  • 43. OakRidge Fission ReactorOakRidge Fission Reactor
  • 44. Production of ElectricityProduction of Electricity
  • 45. NuclearFusionNuclearFusion Nuclearenergy can also be released by fusion of twoNuclearenergy can also be released by fusion of two light elements (elements with low atomic numbers).light elements (elements with low atomic numbers). The powerthat fuels the sun and the stars is nuclearThe powerthat fuels the sun and the stars is nuclear fusion.fusion. In a hydrogen bomb, two isotopes of hydrogen,In a hydrogen bomb, two isotopes of hydrogen, deuterium and tritium are fused to form a nucleusdeuterium and tritium are fused to form a nucleus of helium and a neutron.of helium and a neutron. Unlike nuclearfission, there is no limit on theUnlike nuclearfission, there is no limit on the amount of the fusion that can occur.amount of the fusion that can occur.
  • 46. Applications of NuclearApplications of Nuclear ChemistryChemistry Radioactive Dating using C-14Radioactive Dating using C-14 Treatment of Cancer(Phosphorous andTreatment of Cancer(Phosphorous and Cobalt)Cobalt) NMRand CAT scans in RadiologyNMRand CAT scans in Radiology Sterilization of foodsSterilization of foods Radioactive tracers (cardiology)Radioactive tracers (cardiology) Fission reactors forElectrical PowerFission reactors forElectrical Power Medical Laboratory proceduresMedical Laboratory procedures Defensive and Offensive WeaponsDefensive and Offensive Weapons

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