M42_KNIG9404_ISM_C42.pdf

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1、42NUCLEARPHYSICSConceptualQuestions42.1.(a)161818201818181618OandO(Z=8);andNeandNe(Z=10).(b)O,F,Ne(allhaveA=18).(c)OandO;and18Ne20182016andNe;differentisotopesofthesameelementarechemicallynearlyidentical.(d)OandNe;andOand18Ne.42.2.(a)Morethan,becausetherearesomanymorenucleons.(b)Lesstightlybec

2、auseforAB==200,/A8Mev/nucleon,butforAB==60,/A8.8Mev/nucleon.42.3.(a)Theremustbeanattractiveforcetoholdthenucleustogetherthatwillovercometheelectrostaticrepulsiveforcebetweentheprotons.(b)Thereisnoevidencefornuclearforcesoutsidethenucleus.42.4.(a)Impossible,onlytwoneutronsareallowedinthen=1stat

3、e.(b)Impossible,thepairsofprotonsandneutronsmusthaveonespinupandonespindown.(c)Excitednuclearstatewithoneneutronexcitedtothen=3level.42.5.(a)No,thealphaparticleisaddedtothewrongnucleus.(b)No,theoriginalnucleuswouldneedtolosefournucleons,nottwo.(c)Yes.(d)No,inbetadecayAdoesnotchange.−t/τ⎛⎞N⎛⎞25

4、042.6.NNe=0⇒t=−τln⎜⎟=−(10s)ln⎜⎟=13.86s14s≈⎝⎠N0⎝⎠100042.7.(a)Gammadecaycanlowertheexcitedprotontothen=2level.(b)Beta-minusdecaycanchangeaneutrontoaproton.(c)Nodecayisallowed.42.8.ThenuclearradiationwouldionizesomeofthematterandbreakmolecularbondsinappleA.Thiscoulddrivesomechemicalreactionsthatw

5、ouldnotoccurinappleB.AppleAwouldnotbecomeradioactive.42.9.137Cswouldbemostusefulbecauseafterthebetadecayagammarayisemitted.Alphasandbetasdonotpenetratematerialwell,andsowouldnotcomeoutofthebodytobedetected,butthegammaraypenetratesmaterialwellandsocouldescapethebodyandbedetected.ExercisesandPro

6、blemsSection42.1NuclearStructure42.1.Model:ThenucleusiscomposedofZprotonsandAZ−neutrons.©Copyright2013PearsonEducation,Inc.Allrightsreserved.Thismaterialisprotectedunderallcopyrightlawsastheycurrentlyexist.Noportionofthismaterialmaybereproduced,inanyformorbyanymeans,withoutpermissioninwritingf

7、romthepublisher.42-142-2Chapter42Solve:(a)3HehasZ=2protonsand321−=neutron.(b)32PhasZ=15protonsand321517−=neutrons.(c)32ShasZ=16protonsand321616−=neutrons.(d)238UhasZ=92protonsand23892146−=neutrons.42.2.Model:ThenucleusiscomposedofZproto