Regents Chemistry: Dr. Mintz PracticePacket Chapter2:NuclearChemistry http://mintzchemistry.weebly.com 50
Chapter 2: Nuclear Chemistry Vocabulary Alpha Particles a nuclear particle that contains two protons and two neutrons Artificial Transmutation bombardment of an atom with particles or rays Beta Particle a nuclear particle with zero mass and a negative charge Bombardment - direct a high-speed stream of particles at a substance) Chain reaction a reaction in which one of the products can also serve as one of the reactants, self sustaining once begun Fission the splitting of a nucleus to form smaller fragments Fusion small nuclei combine to form a larger nucleus Gamma Ray high energy electromagnetic radiation Half Life The time required for half the nuclei in a sample of a specific isotope to undergo radioactive decay TABLE N) Natural Transmutation radioactive decay Nuclear Decay the general term for any of several processes alpha emission, beta emission, fission etc.) that an unstable nucleus can undergo in order to achieve stability. Penetrating Power the ability of radiation to pass through objects Radioactivity materials that give off rays or radiation Radiation penetrating rays and particles emitted released) by a radioactive source. TABLE O) Radioisotopes nuclei of unstable isotopes Radioactive Decay when an unstable nucleus releases energy by emitting radiation Transmutation conversion of one element to another element 51
Nuclear Radiation Chemistry 200 Video Lesson 2.1 Objectives Explain how an unstable nucleus releases energy. Describe the three main types of nuclear radiation. Describe what determines the type of decay a radioisotope undergoes. Radioactivity Substances that spontaneously emit give off) radiation Radiation: rays and particles emitted by a radioactive substance o Unstable nuclei release radiation which means they decay) Radioisotopes: nuclei of unstable isotopes Stability of Nuclei Large Atoms o Elements with an atomic number greater than 83 are naturally radioactive. Small atoms o When an atom s mass is not its typical mass o C-13 C-14 Number of neutrons is important to nuclear stability. Neutron : Proton Ratio 1:1 1:1.5) for stability 52
Types of Radiation Types of Radiation These three types of radiation deflect differently as the pass between a pair of electrically charged plates. Penetrating Power Mass Mass Mass Because of their mass and charge, alpha particles Are the least penetrating of the three main types of radiation Charge Charge Charge Natural Transmutation Objective: How do we recognize write out Natural Transmutation reactions? Chemistry 200 Nuclear Chemistry Video Lesson 2.2 53
An unstable nucleus spontaneously decays to form products that are more stable by emiding radiation. This process is called Natural Transmutation because it occurs on its own w/o any outside influence Don t break the Laws!!!! The Laws of Conservation of Mass Charge Natural Transmutation - when nuclei of unstable atoms emit radiation naturally form a new substance - isotopes of new elements may form due to the nuclei becoming unstable There are 3 types of natural transmutation: Alpha Decay Beta Decay Positron Emission - in a nuclear reaction, Mass Charge must be conserved 226 Ra à 222 Rn + 4 He 88 86 2 Alpha Decay: when an unstable nucleus alpha emider) emits an alpha particle becomes more stable - this results in the formation of an atom of a different element The following changes occur when a radioisotope undergoes Alpha Decay: 226 Ra à 222 Rn + 4 He 88 86 2 238 U --> 4 234 92 He + Th 2 90 4 He 2 Beta Decay: - a beta emider, a nucleus that emits a beta particle The following changes occur when a radioisotope undergoes Beta Decay: 214 Po à 214 Bi + 0 e 82 83-1 14 C --> 0 14 6 e + N -1 7 Positron Emission: - a nucleus emits a positron The following occurs when a radioisotope undergoes positron emission: 37 K à 37 Ar + 0 e 19 18 +1 37 Ca --> 0 37 20 e + K +1 19 54
Rules to determine the identity of an unknown reactant or product in a nuclear rxn: Artificial Transmutation Nuclear Energy 1. Find the masses charges of the known particles using Table O the periodic table if necessary 2. Use the Law of Conservation of MaDer mass) to obtain the mass of the unknown particle 3. Use the Law of Conservation of Charge to obtain the charge of the unknown particle 4. If the unknown particle is a form of radiation, find its symbol on Table O 5. If the unknown particle is an element, find its symbol on the periodic table by matching its nuclear charge w/the appropriate atomic # Chemistry 200 Nuclear Chemistry Video Lesson 2.3 Artificial Transmutation Although a stable nucleus does not decay spontaneously, it can be collided w/ high-energy particles to cause Artificial Transmutation Objective: Artificial Transmutation - a transmutation that occurs from bombarding a nucleus w/ high energy particles How is artificial transmutation used to produce nuclear energy? Two types of artificial transmutation: 1. A charged particle proton, alpha particle) is collided w/ a stable nucleus 14N 7 10B 5 7Li 3 + 4He --> 1H + 2 + 1 4He 2 --> 13N 7 + 1H --> 8Be 4 1 17O 8 + 01n Particle Accelerator atom smashers) 2. An uncharged particle neutron) is collided w/ a stable nucleus 6Li 3 32S 16 - devices called cyclotrons synchrotrons use magnetic or electrostatic fields to speed up protons other charged particles--> + 1n à 4He + 3H 0 2 + 1n à 59Co 27 0 + 1n 0 32P 15 à - large amts. of energy can be produced to allow protons or alpha particles to react w/ atomic nuclei 1 + 1H 1 60Co 27 55
Nuclear Energy There are 2 types of nuclear rxns that can produce these extremely large quantities of energy: Nuclear rxns involve energies that are millions of times greater than ordinary chemical rxns. Energies of these magnitudes are often the result of a conversion of mass into energy. Due to this conversion, a small amount of mass is lost and we call this Mass Defect. Fission Fusion 1. Fission to split) - Uranium-235 or Plutonium-239 is struck w/ a neutron causing the atom to split release a large amt of energy in the process E = mc2 - this is used in nuclear reactors atom bombs, this energy is highly radioactive Since the process of fission results in the production of 2 or more neutrons, a Chain Reaction can occur. Chain Reaction - a series of reactions where each reaction is initiated by the energy produced in the previous reaction 1n 0 235U --> 236U --> 142Ba + 91Kr + 3 1n + energy + 92 92 56 36 0 2. Fusion to fuse, join) - light nuclei are joined together to create a heavier element H-->He) along w/ the release of a large amount of energy; this occurs in starssun) in a hydrogen bomb - not a possible source of energy production on earth due to the very high temps up to 150 million C) pressures 1000 s of atm) needed to overcome the repulsions btwn the nuclei 4 11H + 2-10e à - the energy produced is not highly radioactive 56 4He 2 + ENERGY
Objectives Solve problems that involve half-life. Half Life Chemistry 200 Video Lesson 2.4 Half Life Definition o Half Life: is the time it takes for ½ of the atoms of a radioisotope to decay. o Table N Table N Selected Radioisotopes 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 grams After 7.2 days > 12.5 grams After 10.8 days > 6.25 grams Decay of 20.0 mg of 15 O. What remains after 3 half-lives? After 5 half-lives? 57
Example The half life of I-123 is 13 hr. How much of a 64 mg sample of I-123 is left after 26 hours? time Cut in ½ 2 times t 26 Ans: 16 mg = = 2 T 13 ½ life Mass or % or Fraction 64 32 16 Example The half life of I-123 is 13 hr. What is the fraction remaining of I-123 after 26 hours? time Cut in ½ 2 times t Ans: 1/4 T = 26 = 2 13 Mass or % or Fraction 1 1/2 1/4 ½ life Or ½ ) ½) = ¼ # of Half Lives # of Half Lives Example What is the half-life of a radioisotope it 25.0 grams of an original 200 gram sample of the isotopes remains unchanged after 11.46 days? 200 100 50 25 11.46 = 3.82 days 3 Example There are 5.0 g of 131 I left after 40.35 days. How many grams were in the original sample? 160 80 40 20 10 5 Table N 40.35 8.021 d = 5 ANS: 160 g 11.46 days Uses for Radioisotopes Objective: How are radioisotopes helpful? Chemistry 200 Nuclear Chemistry Video Lesson 2.5 58
1. Medical - radioactive isotopes used in the medical field usually have short half-lives so they can quickly be eliminated from the body. Tracers any radioisotope used to follow the path of a material in a system. Iodine-131 - used for detection treatment of thyroid disorders. Cobalt-60 - used to kill cancerous tumors Anthrax Cs-137) Technetium-99 - used in bone brain scans 2. Radiodating Organic material previously living), is dated using Carbon-14 Inorganic material never was living) is usually dated w/ Uranium-238 or Phosphorus-40 3. Commercial - - radiation is used in many other applications from materials strength testing wing of 747) to extending shelf life of fruits, vegetables milk. 59
VideoLesson1:NuclearRadiation Isotopes:Someelementscomeinseveraldifferentforms.Takeuranium,forexample.Most uraniumisuraniumd238.ithas92protonsand146neutrons92+146=238).butthere areseveralotherkindsofuranium.theyallhave92protons,butthenumberofneutrons differs.theyareisotopesofuranium.someisotopesaremorestablethenothers.these unstableisotopecalledradioisotopesandwilldecayspontaneouslytoformmorestable products.asageneralrulethefollowingisotopesareradioisotopesorunstable:. Anyisotopeswithanatomicnumbergreaterthan83isnaturallyradioactive.. Whenanisotopehasamassthatisnotitstypicalmassthemassonthereferencetable) isradioactive. Filloutthechart.Givethecorrectnumberofprotons,atomicnotation,andpredictthe stabilityofeachisotope. Unstable http://mintzchemistry.weebly.com 60
VideoLesson1:NuclearRadiation Definetheterms: 1. Isotope: 2. Radiation: 3. RadioactiveDecay: 4. List2typesofradioactivedecay. Completethetablebelowwiththecorrectinformationabouteachtypeofradioactive emission. Charge AtomicSymbol Alpha Beta Gamma Whichofthefollowingradioactiveemissionsα,β,γ)bestfitthefollowingstatements? 5. Theseemissionsarecharged. 6. Thisemissionisthemostmassive. 7. Thisemissionisthemostcharged. 8. Thisemissionisdangerousoutsidethebody. 9. Thisemissionusstoppedbythinpaper. 10. Thisemissioncantravelthroughpaper,butisstoppedbyaluminum. 11. Thisemissioncantravelthroughfairlythicklead. MultipleChoice 1. Whichgroupofnuclearemissionsislistedinorderofincreasingcharge? 1. Alphaparticle,betaparticle,gammaradiation 2. Gammaradiation,alphaparticle,betaparticle 3. Positron,alphaparticle,neutron 4. Neutron,positron,alphaparticle http://mintzchemistry.weebly.com 61
2. Amixtureofemissionsfromradioactiveatomsispassedthroughelectrically chargedplates,asshowninthediagrambelow. Thenuclearemission1,2,and3arecalledrespectively 1. Gamma,alpha,beta 2. Gamma,beta,alpha 3. Alpha,beta,gamma 4. Beta,gamma,alpha 3. Whichparticlehasthegreatestmass? 1. Analphaparticle 2. Abetaparticle 3. Aneutron 4. Apositron 4. Whichofthesetypesofnuclearradiationhasthegreatestpenetratingpower? 1. Alpha 3. Neutron 2. Beta 4. Gamma 5. Abetaparticlemaybespontaneouslyemittedfrom 1. AgroundDstateelectronconfiguration 2. Astablenucleus 3. Anexcitedelectron 4. Anunstablenucleus ConstructedResponse: Nuclearradiationisharmfultolivingcells,particularlytofastDgrowingcells,suchas cancercellsandbloodcells.anexternalbeamofradiationisemittedfromaradioisotope canbedirectedonasmallareaofapersontodestroycancercellswithinthebody.cobaltd 60isanartificiallyproducedradioisotopethatemitsgammaraysandbetaparticles.One hospitalkeepsa100gsampleofcobaltd60inanappropriate,securestoragecontainerfor futurecancertreatment. 1. ComparethepenetratingpowerofthetwoemissionsfromtheCoD60. http://mintzchemistry.weebly.com 62
VideoLesson2:NaturalTransmutation 1. Whichtypeofradiation alpha,beta,orgamma: 1. Resultsinthegreatestchangeinatomicnumber?Why? 2. Resultsintheleastchangeinatomicnumber?Why? 3. Producesthegreatestchangeinmassnumber?Why? 4. Producestheleastchangeinmassnumber?Why? Rulestodeterminetheidentityofanunknownreactantorproductinanuclear reaction: 1. FindthemasseschargesoftheknownparticlesusingTableOtheperiodictable ifnecessary 2. UsetheLawofConservationofMattertoobtainthemassoftheunknownparticle 3. UsetheLawofConservationofChargetoobtainthechargeoftheunknownparticle. 4. Iftheunknownparticleisaformofradiation,finditssymbolonTableO 5. Iftheunknownparticleisanelement,finditssymbolontheperiodictableby matchingitsnuclearchargew/theappropriateatomic# PracticeExamples Alpha,BetaorPositron) 1. 233 U! 4 He+ DecayMode= 92 2 2. 234 Th! 234 Pa+ DecayMode= 90 91 3.! 0 e+ 90 Y DecayMode= +1 4. 19 Ne! 0 e+ DecayMode= +1 5. 53 Fe! 53 Mn+ DecayMode= 26 6. 222 Rn! 218 Po+ DecayMode= 7.! 216 At+α DecayMode= 85 8. 99 Ag!β + + DecayMode= 9.!β O + 14 N DecayMode= http://mintzchemistry.weebly.com 63
TableNliststhemostcommondecaymodesfornucleithatundergonaturalradioactivity Writebalancedequationsforeachofthefollowingnuclearreactions: 1. naturaldecayofpud239 2. naturaldecayofhydrogend3 3. naturaldecayofkd37 4. naturaldecayofphosphorusd32 5. naturaldecayofud235 6. naturaldecayofcalciumd37. KryptonD85undergoesnaturaldecay. NeD19emitsapositron. ThoriumD232undergoesnaturaldecay TcD99emitsabetaparticle. IronD53undergoesnaturaldecay. FrD220emitsanalphaparticle http://mintzchemistry.weebly.com 64
MultipleChoice 1. Whichtermidentifiesatypeofnuclearreaction? 1. Transmutation 3. Deposition 2. Neutralization 4. Reduction 2. Inwhichtypeofreactionisanatomofoneelementconvertedtoanatomofa differentelement? 1. Decomposition 3. Saponification 2. Neutralization 4. Transmutation 3. Whichequationrepresentsnaturaltransmutation? 10 1. 5!+4 2!"!10 5!+10 5! 3. S+2e D!S 2D 4. Na!Na 1 + +e D 2. 6!!14 7!+eD 4. Intheequation: 239 90!h!239 91!"+X ThesymbolXrepresents 0 1. +1! 1 3.!! 0 2. 1! 1 4. 1! 5. RadioactivecobaltD60isusedinradiationtherapytreatment.CobaltD60 undergoesbetadecay.thistypeofnuclearreactioniscalled 1. Naturaltransmutation 2. Artificialtransmutation 3. Nuclearfusion 4. Nuclearfission http://mintzchemistry.weebly.com 65
Lesson3:ArtificialTransmutationandNuclearEnergy ArtificialTransmutationisatransmutationthatoccursfrombombardingastable nucleuswithhighdenergyparticlesproton,neutronoralphaparticle) Writebalancednuclearequationsforthefollowingreactions: 1. KD42reactsw/aneutrontoproduceanalphaparticleanothersubstance. 2. RubidiumD85reactsw/aprotontoproduceaneutronanothersubstance. 3. CollidingNitrogenD14w/aneutrontoproduceaprotonanothersubstance. 4. BeD9iscollidedw/anotherparticletoproduceLiD6HeD4. 5. AlD27isbombardedw/analphaparticletoproduceaneutronanothersubstance. http://mintzchemistry.weebly.com 66
NuclearEnergy:Nuclearreactionsinvolveenergiesthataremillionsoftimesgreaterthan ordinarychemicalreactions.energiesofthesemagnitudesareoftentheresultofthe conversionofmassintoenergy. Thereare2typesofnuclearreactionsthatcanproducetheseextremelylarge quantitiesofenergy:fissionfusion. 1 0!+235 92!!236 92!!142 56!"+91 36!"+31 0!+energy 2 1!+2 1!!4 2!"+energy MultipleChoice: 1. Highenergyisarequirementforfusionreactionstooccurbecausethenuclei involved 1. attracteachotherbecausetheyhavelikecharges 2. attracteachotherbecausetheyhaveunlikecharge 3. repeleachotherbecausetheyhavelikecharge 4. repeleachotherbecausetheyhaveunlikecharges 2. Whenauraniumnucleusbreaksupintofragments,whichtypeofnuclear reactionoccurs? 1. fusion 2. fission 3. replacement 4. redox 3. Whichpairofnucleicanundergoafusionreaction? 1. potassiumd40cadmiumd11 2. zincd64calciumd44 3. uraniumd238leadd208 4. hydrogend2hydrogend3 4. Whichprocessisrepresentedbythefollowingreaction? 2 1!+2 1!!4 2!"+energy 1. fission 3. artificialtransmutation 2. fusion 4. alphadecay 5. Duringafissionreaction,whichtypeofparticleiscapturedbyanucleus? 1. deuteron 2. electron 3. neutron 4. proton http://mintzchemistry.weebly.com 67
6. Whatistheprimaryresultofafissionreaction? 1. conversionofmasstoenergy 2. conversionofenergytomass 3. bindingtogetheroftwoheavynuclei 7. Comparedtoanordinarychemicalreaction,afissionreactionwill: 1. releasesmalleramountofenergy 2. releaselargeramountsofenergy 3. absorbsmallamountsofenergy 4. absorblargeramountsofenergy 8. Whichtypeofreactionproducesenergyintenselyradioactivewaste products? 1. fusionoftritiumdeuterium 2. fissionofuranium 3. burningofheatingoil 4. burningofwood 9. Whichprocessoccursinacontrolledfusionreaction? 1. lightnucleicollidetoproduceheaviernuclei 2. heavynucleicollidetoproducelighternuclei 3. neutronbombardmentsplitslightnuclei 4. neutronbombardmentsplitsheavynuclei 10. Considerthefollowingreaction: 1 n+ 235 UDD> 236 UDD> 142 Ba+ 91 Kr+3 1 n+energy 0 92 92 56 36 0 Thisequationisanexampleof: 1. Fission 2. fusion 3. naturaldecay 4. endothermic 11. Whichriskisassociatedwithusingnuclearfissiontoproduceenergyina powerplant? 1. Depletionofhydrocarbons 2. Depletionofatmosphericoxygen 3. Exposureofworkerstoradiation 4. Exposureofworkerstosulfurdioxide http://mintzchemistry.weebly.com 68
http://mintzchemistry.weebly.com VideoLesson4:HalfLife 1. Howmanygramsofradonwouldbepresentafter4days? 2. Howmanygramsofradonwouldbepresentafter12days? 3. Howmanygramsofradonwouldbepresentafter24days? 4. If8gofradonareleft,whatisthetimethatelapsed? 5. Howmanygramsofradonwouldbepresentafter6days? 69
AhalfOlifeisthetimerequiredforhalfofasampleofradioactivesubstanceto disintegrate.aftertwohalfolives,oneoquarteroftheoriginalsamplewillremain,and soon. 1. Howmuchofa200.0gsampleof 198 Auisleftafter8.10daysifitshalfDlifeis2.70days? 2. A100.0gsampleof 16 Ndecaysto12.5gin14.4seconds.WhatisthehalfDlife? 3. ThehalfDlifeof 42 Kis12.4hours.Howmuchofa500.0gsampleisleftafter62.0hours? 4. WhatisthehalfDlifeof 99 Tcifa750.0gsampledecaysto46.875gin639,000years? 5. CoD60halfDlifeis5.271a,approximatelywhatfractionofCoD60sampleremainsafter 21.084years? 6. AsampleofgoldD198decaysto1.0gin13.475days.GoldD198hasahalfDlifeof2.695 days.whatwasthemassoftheoriginalsample? 7. An80mgsampleofaradioactiveisotopedecaysto5mgin32days.WhatisthehalfDlife ofthiselement? http://mintzchemistry.weebly.com 70
MultipleChoice: 1. Whatisthetotalnumberofyearsthatmustpassbeforeonly25.00gramsofan original100.00gramsampleofcd14remainsunchanged? 1. 2865y 3. 114 0y 2. 57y 4. 17190y 2. WhichnuclidehasahalfDlifethatislessthanoneminute? 1. CesiumD137 3. PhosphorusD32 2. FranciumD220 4. StrontiumD90 3. Whichfractionofanoriginal20.00gramsampleofnitrogenD16remains unchangedafter3 seconds? 1. 1/5 2. 1/8 3. 1/16 4. 1/32 4. Whatisthehalf lifeanddecaymodeofrnd222? 1. 1.91daysandalphadecay 2. 1.91daysandbetadecay 3. 3.82daysandalphadecay 4. 3.82daysandbetadecay 5. After32days,5milligramsofan80milligramsampleofaradioactiveisotope remainsunchanged.whatisthehalfdlifeofthiselement? 1. 8days 2. 2days 3. 16days 4. 4days ConstructedResponse: Baseyouranswertothenext2questionsontheinformationbelowandonyourknowledgeof chemistry. IlluminatedEXITsignsareusedinpublicbuildingssuchasschools.IfthewordEXITis green,thesignmaycontaintheradioisotopetritium,hydrogend3.thetritiumisagas sealedinglasstubes.theemissionsfromthedecayofthetritiumgascauseacoatingonthe insideofthetubestoglow. 1. Completethenuclearequationfortheradioactivedecayoftritium,bywritinga notationforthemissingproduct. 3 1!! 0 1!+ 2. Determinethefractionofanoriginalsampleoftritiumthatremainsunchangedafter 24.62years. http://mintzchemistry.weebly.com 71
Name Half-Life Practice Date 1. Base your answer to the following question on the information below. The radioisotopes carbon-14 and nitrogen-16 are present in a living organism. Carbon-14 is commonly used to date a once-living organism. A sample of wood is found to contain 1/8 as much C-14 as is present in the wood of a living tree. What is the approximate age, in years, of this sample of wood? 2. A radioactive isotope has a half-life of 2.5 years. Which fraction of the original mass remains unchanged after 10. years? A) 1/2 B) 1/4 C) 1/8 D) 1/16 3. What fraction of a Sr-90 sample remains unchanged after 87.3 years? A) 1 2 B) 1 3 C) 1 4 D) 1 8 4. After decaying for 48 hours, of the original mass of a radioisotope sample remains unchanged. What is the half-life of this radioisotope? A) 3.0 h B) 9.6 h C) 12 h D) 24 h 5. What is the total number of years that must pass before only 12.50 grams of an original 100.0-gram sample of C-14 remains unchanged? A) 2865 y B) 5730 y C) 11 460 y D) 17 145 y 6. What is the half-life of a radioisotope if 25.0 grams of an original 200.-gram sample of the isotope remains unchanged after 11.46 days? A) 2.87 d B) 3.82 d C) 11.46 d D) 34.38 d 7. An original sample of a radioisotope had a mass of 80.0 milligrams. Only 20.0 milligrams of this original sample remain unchanged after 8.32 seconds. What is the half-life of this radioisotope? A) 1.04s B) 2.08s C) 4.16s D) 8.3s 8. In how many days will a 12-gram sample of decay, leaving a total of 1.5 grams of the original isotope? A) 8.0 B) 16 C) 20. D) 24 72
VideoLesson5:UsesforRadioisotopes Radiationisusedbydoctorstodiagnoseillnessandhelpsarchaeologistsfindtheageof ancientartifacts.electricityproducedbynuclearfissionddsplittingtheatomddisoneofitsgreatest uses.areliablesourceofelectricityisneededtogiveuslight,helptogroomandfeedus,andto keepourhomesandbusinessesrunning.letmegiveyousomespecificexamplesofhowthe radiationhasbeenusedtodd Diagnoseandtreatillnesses Killbacteriaandpreservefoodwithoutchemicalsandrefrigeration Processsludgeforfertilizerandsoilconditioner Locateundergroundnaturalresourcesandtelladryholefromagusher Makesmokedetectors,nonstickfrypans,andicecream Growstrongercrops Powersatellitesandprovidefutureelectricalneedsforspacelaboratorieswith peopleonboard Designinstruments,techniques,andequipment;measureairpollution Provetheageofworksofartandassistindeterminingtheirauthenticity RADIATIONINMEDICINE XDraysareatypeofradiationthatcanpassthroughourskin.Ourbonesaredenserthanour skin,sowhenxdrayed,bonesandotherdensematerialscastshadowsthatcanbedetectedon photographicfilm.theeffectissimilartoplacingapencilbehindapieceofpaperandholdingthem infrontofalight.theshadowofthepencilisrevealedbecausemostlighthasenoughenergyto passthroughthepaper,whilethedenserpencilstopsallthelight.thedifferenceisthatweneed filmtoseethexdraysforus. Today,doctorsanddentistsusexDraystoseestructuresinsideourbodies.Thisallowsthem tospotbrokenbonesanddentalproblems.xdraymachineshavenowbeenconnectedtocomputers inthedevelopmentofmachinescalledcatscanners.theseinstrumentsprovidedoctorswithcolor TVpicturesthatshowtheshapeofinternalorgans. Approximately10millionnuclearmedicineproceduresareperformedintheUnitedStates annually.diagnosticxdraysandorradiationtherapywereadministeredtoaboutsevenoutofevery 10Americans.Medicalproceduresusingradiationhavesavedthousandsoflivesthroughthe detectionandtreatmentofconditionsrangingfromhyperthyroidismtobonecancer. Insuchprocedures,doctorsadministerslightlyradioactivesubstancestopatients,which areattractedtocertaininternalorganssuchasthepancreas,kidney,thyroid,liver,orbrain,to diagnoseclinicalconditions.moreover,radiationisoftenusedtotreatcertaintypesofcancer. Radioactiveiodine,specificallyiodineD131,isbeingusedfrequentlytotreatthyroidcancer,a diseasewhichstrikesabout11,000americanseveryyear. RADIATIONINSCIENCE Radiationisusedinscienceinmanyways.Justasdoctorscanlabelsubstancesinside people'sbodies,scientistscanlabelsubstancesthatpassthroughplants,animals,orourworld.this allowsustostudysuchthingsasthepathsthatdifferenttypesofairandwaterpollutiontake throughtheenvironment. Ithasalsohelpeduslearnmoreaboutawidevarietyofthings,suchaswhattypesofsoil differentplantsneedtogrow,thesizeofnewlydiscoveredoilfields,andthetrackofocean currents. Scientistsuseradioactivesubstancestofindtheageofancientobjectsbyaprocesscalled carbondating.forexample,intheupperlevelsofouratmosphere,cosmicrayshitnitrogenatoms andformanaturallyradioactiveisotopecalledcarbond14.carbonisfoundinalllivingthings,anda smallpercentageofthiscarboniscarbond14.whenaplantoranimaldies,itnolongertakesinnew carbonandthecarbond14itcontainsbeginstheprocessofradioactivedecay. http://mintzchemistry.weebly.com 73
http://mintzchemistry.weebly.com However,newisotopesofcarbonD14continuetobeformedinouratmosphere,andaftera fewyearsthepercentofradioactivityinanoldobjectislessthanitisinanewerone.bymeasuring thisdifference,scientistsareabletodeterminehowoldcertainobjectsare.themeasuringprocess iscalledcarbondating. RADIATIONININDUSTRY Wecouldtalkalldayaboutthemanyandvariedusesofradiationinindustryandnot completethelist.tomakealongstoryshort,we'lljustconcentrateonafew.exposuretosome typesofradiationforexample,xdrays)cankillgermswithoutharmingtheitemsthatarebeing disinfectedormakingthemradioactive.forexample,whentreatedwithradiation,foodstakemuch longertospoil,andmedicalequipmentsuchasbandages,hypodermicsyringes,andsurgical instrumentsdon'thavetobeexposedtotoxicchemicalsorextremeheattobesterilized.although wenowusechlorine,atoxicanddifficultdtodhandlechemical,wemayuseradiationinthefutureto disinfectourdrinkingwaterandevenkillallthegermsinoursewage.ultravioletlightisalready beingusedtodisinfectdrinkingwaterinsomehomes. Theagriculturalindustrymakesuseofradiationtoimprovefoodproduction.Plantseeds, forexample,havebeenexposedtoradiationtobringaboutnewandbettertypesofplants.besides makingplantsstronger,radiationcanalsobeusedtocontrolinsectpopulations,therebydecreasing theuseofpesticides. EngineersuseradioactivesubstancestomeasurethethicknessofmaterialsandanxDrayprocess calledradiographytofindhardtodetectdefectsinmanytypesofmetalsandmachines. Radiographyisalsousedtochecksuchthingsastheflowofoilinsealedenginesandtherateand wayvariousmaterialswearout.andwe'vealreadytalkedabouttheuseoftheradioactiveelement uranium,whichisusedasafueltomakeelectricityforourcities,farms,towns,factories,etc. Inouterspace,radioactivematerialsarealsousedtopowerspacecraft.Suchmaterialshave alsobeenusedtosupplyelectricitytosatellitessentonmissionstotheoutermostregionsofour solarsystem. Radiationhasbeenusedtohelpcleanuptoxicpollutants,suchasexhaustgasesfromcoalDfired powerstationsandindustry.sulfurdioxidesandnitrogenoxides,forexample,canberemovedby electronbeamradiation. Asyoucansee,radiationandradioactivematerialshaveplayedandwillcontinuetoplaya verysignificantroleinourlives.let'ssumupthisdiscussionwithawalkthroughthelifeofa typicalfamilyforonedayandlearnaboutsomeoftheusesofradiation. Dadgetsupinthemorningandputsonacleanshirt.HispolyesterDcottonblendshirtis madefromchemicallytreatedfabricthathasbeenirradiatedtreatedwithradiation)beforebeing exposedtoasoildreleasingagent.theradiationmakesthechemicalsbindtothefabric,keepinghis shirtfreshandpressedallday.theshirtisnotradioactive. Inthekitchen,Jennyisfryinganegg.Thatnonstickpansheisusinghasbeentreatedwith gammarays,andthethicknessoftheeggshellwasmeasuredbyagaugecontainingradioactive materialbeforegoingintotheeggcartoon.thin,breakableeggswerescreenedout.theturkey Momistakingoutoftherefrigeratorfortonight'sdinnerwascoveredwithirradiatedpolyethylene shrinkdwrap.oncepolyethylenehasbeenirradiated,itcanbeheatedaboveitsusualmeltingpoint andwrappedaroundtheturkeytoprovideanairtightcover. AsDaddrivestowork,hepassesreflectivesignsthathavebeentreatedwithradioactive tritiumandphosphorescentpaint.duringlunch,brotherbobhassomeicecream.theamountofair whippedintothaticecreamwasmeasuredbyaradioisotopicgauge.afteryouandyourfamily returnhomethisevening,someofyoumayhavesodaandothersmaysitandrelax.nuclearscience isatworkhere:thesodabottlewascarefullyfilledddaradiationdetectorpreventedspillover.and yourfamilyissafeathomebecausetheionizingsmokedetector,usingatinybitofamericiumd241, willkeepwatchoveryouwhileyousleep. 74
Questions: 1. Howcanweuseradioactiveisotopestodetectillness? 2. Howcanweuseradiationtodetectweaknessintheconstructionofbuildings? 3. HaveyoueverhadabonexDray?TeethxDrayed?Howdidthishelpyourdoctoror dentisttreatyou? 4. DoyouthinkadditionalradiationreceivedwhenpeoplehavemedicalxDrays,about 40milliremsperyear,isworththebenefitstheyreceive? 5. Arethereadvantagestousingradiationinsteadofpesticidestocontrolpests,such asinsects? MultipleChoice: 1. Thedecayofwhichradioisotopecanbeusedtoestimatetheageofthe fossilizedremainsofaninsect? 1. RnD222 2. ID131 3. CoD60 4. CD14 2. Whichradioisotopeisusedfordiagnosingthyroiddisorders? 1. UD238 3. ID131 2. PbD206 4. CoD60 3. CobaltD60andidodineD131areradioactiveisotopesthatareusedin 1. Datinggeologicalformations 2. Industrialmeasurements 3. Medicalprocedures 4. Nuclearpower 4. Whichradioactiveisotopeisusedintreatingcancer? 1. CarbonD14 2. CobaltD60 3. LeadD206 4. UruaniumD238 http://mintzchemistry.weebly.com 75
5. Thecourseofachemicalreactioncanbetracedbyusinga 1. Polarmolecule 2. Diatomicmolecule 3. Stableisotope 4. Radioisotope ConstructedResponse: Baseyouranswertothenext3questionsontheinformationbelowandonyourknowledgeof chemistry. CobaltD60iscommonlyusedasasourceofradiationforthepreventionoffood spoilage.bombardingcobaltd59nucleiwithneutronsproducesthenuclidecobaltd60.a foodirradiationfacilityreplacesthecobaltd60,asourceofgammarays,whenthe radioactivitylevelfallsto1/8ofitsinitiallevel.thenuclidecesiumd137isalsoasourceof radiationforthepreventionoffoodspoilage 1. CompletethenuclearequationbelowforthedecayofcesiumD137.Yourresponse mustincludethesymbol,atomicnumber,andmassnumberofthemissingparticle. 137 55!"! 0 1!+ 2. DeterminethetotalnumberofyearsthatelapsebeforeanoriginalcobaltD60source inanirradiationfacilitymustbereplaced. 3. IdentifyoneemissionspontaneouslyreleasedbyacobaltD60nucleus. http://mintzchemistry.weebly.com 76
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