TheThe AtomicAtomic NucleusNucleus
DiscoveryDiscovery ofof RadioactivityRadioactivity
LeadLead blockblock RadiumRadium LeadLead blockblock MagnetMagnet
RadiumRadium LeadLead blockblock
αα αα
AlphaAlpha particleparticle (helium(helium nucleus)nucleus) ββ ββ
BetaBeta particleparticle (electron)(electron) γγ γγ
GammaGamma rayray (ultra-high(ultra-high energyenergy nonvisiblenonvisible light) light) γγ αα
ββ RadioactiveRadioactive SourceSource
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AluminumAluminum
LeadLead RadioactiveRadioactive SourceSource αα PaperPaper
AluminumAluminum
LeadLead RadioactiveRadioactive SourceSource
PaperPaper ββ
AluminumAluminum
LeadLead RadioactiveRadioactive SourceSource
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AluminumAluminum γγ
LeadLead RadioactivityRadioactivity IsIs aa NaturalNatural PhenomenonPhenomenon OriginsOrigins ofof radiationradiation exposureexposure OriginsOrigins ofof radiationradiation exposureexposure
Natural Background (cosmic rays, earth minerals) 81%
Medicine and Diagnostics 15% Consumer Products (televisions sets, smoke detectors) 4% UnitUnit ofof radiationradiation exposureexposure UnitUnit ofof radiationradiation exposureexposure
radrad UnitUnit ofof radiationradiation exposureexposure
0.010.01 joulejoule radiantradiant energyenergy radrad == kilogramkilogram ofof tissuetissue SomeSome formsforms ofof radiationradiation areare moremore harmfulharmful toto livingliving organismsorganisms thanthan others…others… AbilityAbility toto causecause harmharm isis givengiven inin “rem“rem””
remrem == radrad x x factorfactor HealthHealth ParticleParticle DosageDosage FactorFactor effecteffect HealthHealth ParticleParticle DosageDosage FactorFactor effecteffect
alphaalpha 11 radrad x 1010 = 1010 remrem HealthHealth ParticleParticle DosageDosage FactorFactor effecteffect
alphaalpha 11 radrad x 1010 = 1010 remrem
betabeta 1010 radrad x 11 = 1010 remrem 11 remrem == 10001000 milliremmillirem (mrem(mrem)) AverageAverage annualannual exposureexposure perper personperson InIn thethe UnitedUnited StatesStates
aboutabout 360360 mremmrem Major Source Radon - 222 TypicalTypical AnnualAnnual RadiationRadiation ExposureExposure Source TypicalTypical AmountAmount Source ReceivedReceived inin 11 YearYear NaturalNatural OriginOrigin (millirems)(millirems) Cosmic radiation 26 Ground 33 Air (radon-222) 198 Human tissues (postassium-40; radium-226) 35 HumanHuman OriginOrigin Medical procedures Diagnostic X rays 33 Nuclear medicine 15 Television tubes, other consumer products 11 Weapons-test fallout 1 RadioactiveRadioactive IsotopesIsotopes AreAre UsefulUseful asas TracersTracers andand forfor MedicalMedical ImagingImaging UsesUses ofof SomeSome RadioactiveRadioactive IsotopesIsotopes IsotopeIsotope UsageUsage Calcium-47 Study of bone formation in mammals Californium-252 Inspect airline luggage for explosives Hydrogen-3 (tritium) Life-science and drug-metabolism studies to ensure safety of potential new drugs Iodine-131 Diagnose and treat thyroid disorders Iridium-192 Test integrity of pipeline welds, boilers, and aircraft parts Thallium-201 Cardiology and for tumor detection Xenon-133 Lung-ventilation and flood-flow studies
Source: Nuclear Regulatory Council RadioactivityRadioactivity ResultsResults fromfrom anan ImbalanceImbalance ofof ForcesForces inin thethe NucleusNucleus HeliumHelium nucleusnucleus StrongStrong NuclearNuclear ForceForce
AnAn attractiveattractive forceforce thatthat actsacts betweenbetween allall nucleonsnucleons
TheseThese protonsprotons areare notnot normallynormally attractedattracted toto eacheach otherother NeutronsNeutrons areare neededneeded toto createcreate thethe strongstrong nuclearnuclear forceforce ThereThere isis aa limitlimit toto thethe numbernumber ofof neutronsneutrons thatthat cancan bebe addedadded toto anan atomicatomic nucleus…nucleus… …neutrons…neutrons needneed toto havehave protonsprotons aroundaround themthem inin orderorder toto remainremain stable…stable… …with…with tootoo manymany neutrons,neutrons, andand notnot enoughenough protons,protons, somethingsomething mostmost bizarrebizarre occurs…occurs… AA lonelone neutron…neutron…
…converts…converts toto aa proton!proton!
ProtonProton toto NeutronNeutron ratiosratios ProtonProton toto NeutronNeutron ratiosratios
OptimumOptimum 11 toto 11 ProtonProton toto NeutronNeutron ratiosratios
OptimumOptimum 11 toto 11
LimitLimit 11 toto 1.41.4 AA nucleusnucleus withwith “too“too manymany neutrons”neutrons” AA nucleusnucleus withwith “too“too manymany neutrons”neutrons”
HmmHmm…extra…extra proton?proton?
TheThe sizesize ofof thethe nucleusnucleus isis limitedlimited
1)1) The The nucleusnucleus cannotcannot holdhold aa veryvery largelarge numbernumber ofof protonsprotons together.together. 2)2) ThereThere cannotcannot bebe anan unlimitedunlimited numbernumber ofof neutrons.neutrons. AA RadioactiveRadioactive ElementElement CanCan TransmuteTransmute toto aa DifferentDifferent ElementElement TransmutationTransmutation
TheThe changingchanging ofof oneone elementelement toto anotheranother 238238 U 9292 U 234234 Th44 He 9090 Th22 He 234234 Th 44 He 9090 Th 22 He 234234 Th 44 He 9090 Th 22 He 234234 Th 9090 Th 238238 U 9292 U 234234 Th44 He 9090 Th22 He 234234 Th 44 He 9090 Th 22 He 234234 Th 44 He 9090 Th 22 He 234234 Th 9090 Th ++ ++ ++
238238 234234 44 UU ThTh ++ HeHe 9292 9090 22 ++ ++ ++
234234 234234 00 ThTh PaPa ++ ee 9090 9191 -1-1 RadioactiveRadioactive Half-LifeHalf-Life
TheThe timetime itit takestakes forfor one-halfone-half ofof aa radioactiveradioactive samplesample toto decaydecay ElementElement Half-LifeHalf-Life
99 UraniumUranium-238-238 4.54.5 xx 1010 yearsyears ElementElement Half-LifeHalf-Life
99 UraniumUranium-238-238 4.54.5 xx 1010 yearsyears
Carbon-14Carbon-14 57305730 yearsyears ElementElement Half-LifeHalf-Life
99 UraniumUranium-238-238 4.54.5 xx 1010 yearsyears
Carbon-14Carbon-14 57305730 yearsyears
Bismuth-210Bismuth-210 5.05.0 daysdays ElementElement Half-LifeHalf-Life
99 UraniumUranium-238-238 4.54.5 xx 1010 yearsyears
Carbon-14Carbon-14 57305730 yearsyears
Bismuth-210Bismuth-210 5.05.0 daysdays
-- 4 4 PoloniumPolonium-214-214 1.61.6 xx 1010 secsec
RadioactiveRadioactive Half-LifeHalf-Life TheThe timetime itit takestakes forfor one-one- halfhalf ofof aa radioactiveradioactive samplesample toto decaydecay
LookLook atat factorsfactors ofof 22 OneOne half-lifehalf-life (1/2)(1/2) TwoTwo half-liveshalf-lives (1/4)(1/4) ThreeThree half-liveshalf-lives (1/8)(1/8)
ForFor Example:Example: AA materialmaterial hashas decreaseddecreased byby ¼¼ of of itsits originaloriginal amountamount itit hashas gonegone throughthrough twotwo half-liveshalf-lives
N-14 N-14
7 7 N-14 N-14 N-14
C-14 C-14 C-14 C-14 C-14
6 8 C-14 14 CO 2 14 CO 2
Carbon-14Carbon-14 isis aa radioactiveradioactive isotopeisotope thatthat isis naturallynaturally incorporatedincorporated fromfrom carboncarbon dioxidedioxide intointo livingliving organisms,organisms, thethe amountamount remainsremains relativelyrelatively constantconstant duringduring thethe lifelife ofof thethe organismorganism
WhenWhen thethe livingliving organismsorganisms diesdies thethe carboncarbon 1414 isis nono longerlonger beingbeing replacedreplaced inin thethe organismorganism andand willwill startstart toto decay.decay. TheThe amountamount ofof lossloss fromfrom thethe thatthat comparedcompared toto livingliving organismsorganisms cancan bebe usedused toto determinedetermine whenwhen thethe organismorganism died.died. 22,92022,920 yearsyears agoago 17,19017,190 yearsyears agoago 11,46011,460 yearsyears agoago 57305730 yearsyears agoago PresentPresent
CalculateCalculate AgeAge
Problem:Problem: TheThe carbon-14carbon-14 radioactivityradioactivity inin thethe bonesbones ofof aa bodybody waswas measuredmeasured toto bebe 1/81/8 ofof thatthat comparedcompared toto aa livingliving personperson
HowHow longlong agoago diddid thethe personperson live?live? CalculateCalculate AgeAge
CalculationCalculation ofof Age:Age: TheThe carbon-14carbon-14 hashas decreaseddecreased byby 1/81/8 whichwhich isis threethree halfhalf liveslives (1/2(1/2 timestimes 1/21/2 timestimes 1/21/2 == 1/8)1/8)
Carbon-14Carbon-14 halfhalf lifelife == 57305730 yearsyears
33 timestimes 57305730 == 17,19017,190 yearsyears PresentPresent OneOne Half-LifeHalf-Life 57305730 yearsyears agoago TwoTwo Half-LivesHalf-Lives 11,46011,460 yearsyears agoago ThreeThree Half-LivesHalf-Lives 17,19017,190 yearsyears agoago