Unstable Isotope Decay不稳定同位素的衰变.ppt

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1、UnstableIsotopeDecayHalfLifeANotefromYesterdayHereisadecayseriesofanelement.Elementswillundergoalphaandbetadecays.Half-Life:Thetimeittakesforhalfoftheradioactivenucleiinagivensampletoundergodecay.Mostallelementsabove92areradioactive…becausetheydon’tfollowthebandofstability(LinkedtotheP:N

2、Ratio)CommonRadioactiveIsotopesIsotopeHalf-LifeRadiationEmittedCarbon-145,730yearsb,gRadon-2223.8daysaUranium-2357.0x108yearsa,gUranium-2384.46x109yearsaNuclearDecayWhileeachradioisotopedecaysatadifferentrate……theyalldecayataconstantrate.Noenvironmentalfactorswillchangehowfasttheirnucleu

3、sbreaksapart.RadioactiveHalf-LifeAfteronehalflifethereis1/2oforiginalsampleleft.Aftertwohalf-lives,therewillbe…1/2ofthe1/2=1/4theoriginalsample.Afterthreehalf-lives,therewillbe…½ofthe¼=1/8theoriginalsample.ExampleProblem#1Youhave100gofradioactiveC-14.Thehalf-lifeofC-14is5730years.Howmany

4、gramsareleftafteronehalf-life?Howmanygramsareleftaftertwohalf-lives?Howmuchtimehaselapsedafter4halflives?ExampleProblem#2Asampleof56.0gramsofRadonaretrappedinasealedbasement.Thehalf-lifeofRadonis4days.HowmanygramsofRadonareleftafter24days?Howmuchisleftafter8days?Answer:0.875grams14gramsR

5、emainingNucleivsTimeAnInterestingNote…Lavoisierwasmostnotedfor…?…Anadditionalpiecetothis“Law”…istheword,“CHEMICAL”Unfortunately,thisdoesn’tapplytoNUCLEARreactions……Therefore,massactuallyCANbedestroyedduringnuclearreactions.ChemicalNuclearE=mc2