nuclear chemistry - seneca high school homepage：核化学塞内卡中学主页

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1、NuclearChemistryChapter25WhatdoyouthinkofwhenyouhearNuclearChemistry?HistoryHenriBecquerel(1852-1908)OriginallythoughtsunlightcauseduraniumtoradiateDiscoveredthespontaneousradiationwhilewaitingforasunnydaytotesthistheoryMarieCurie(1867-1934)andherhusbandPierreCurie(1859-1906)Workedw/Becque

2、relEventuallyshowedthattherayswerefromuraniumatomsCameupwiththeterm“radioactivity”todescribeRadiation–penetratingraysandparticlesemittedbyaradioactivesource.RadiationAnunstablenucleusreleasesenergybyemittingradiationduringtheprocessofradioactivedecay.Whatisanunstablenucleus?Stabilitydepend

3、softheneutrontoprotonratio.Atomswithlowatomicnumbers(1-20)havea1:1ratio.Above20,stablenucleihavea1.5:1ratio.AlphaDecay-AlphaDecay,AlphaParticles,Radioactivity-PhETTypesofRadiationAlphaRadiation-whenaheliumnucleihasbeenemittedfromaradioactivesource.TypesofRadiationBetaRadiation–Anelectronre

4、sultingfromthebreakingapartofaneutroninanatom.TypesofRadiationGammaRadiation–ahigh-energyphotonemittedbyaradioisotope.(electromagneticradiation)ExtremelyDangerous!SummaryofRadiationALPHAPositivematterExactlylikeaHeliumnucleusBETANegativematterExactlylikeanelectronGAMMAHighenergywaveNOTmatt

5、ersonochargeTypesofDecayneutrontoprotonratiodeterminesthetypeofdecayFourTypesofDecayBetaDecayElectronCapturePositronEmissionAlphaDecayBetaDecayTooManyNeutrons!BetaDecay–neutronturnedintoaprotonandelectron10n11H+0-1eExample:146C147N+0-1eElectronCaptureToofewneutrons!ElectronCapture–convertp

6、rotontoneutron;ane-iscaptured.Example:3718Ar+0-1e3717ClPositronEmissionPositron–particlewiththemassofanelectronbutapositivechargeAprotonchangestoaneutron.Example:85B84Be+0+1eAlphaDecayToomanyneutronsandtoomanyprotons!Mostcommoninatomswithanatomicnumbergreaterthan83.AlphaEmission–releaseofa

7、nalphaparticle.Example:22688Ra22286Rn+42HeTheblueoneshaveatleastonestableisotope.Othersdonot!http://catalog.flatworldknowledge.comHalf-LifeHalf-life:isthetimerequiredforonehalfofthenucleiofaradioisotopesampletodecaytostableproducts.