原子结构AtomicStructure

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1、AtomicStructure(P11-14)1.NucleusThiscontainsprotonsandneutrons,calledcollectivelynucleons.2.Themassnumbergivesthenumberofnucleons,thatisthenumberofprotons+neutrons.3.Theatomicnumbergivesthenumberofprotonsinthenucleus.Italsogivesthenumberofelectronsin

2、theneutralatomandthepositionoftheelementintheperiodictable.4.Isotopesareatomswiththesameatomicnumberbutdifferentmassnumbers.5.Themassesofatomsofparticularisotopes,calledtherelativeisotopicmass,areexpressedonarelativescaleonwhichthemassofanatomoftheis

3、otopecarbon-12has12unitsexactly.6.RelativeatomicmassAllelementsexistinseveralisotopicformsanditisusefultohaveanaveragevaluefortheatomsofeachelement.Thisiscalledtherelativeatomicmassandisdefinedastheweighedmeanofthemassesofthenaturallyoccurringisotope

4、softheelementexpressedonthecarbon-12scale.(Anexampleisshownbelow.P11)7.RadioactivitySomeisotopesarestable,butothers,oftenwithunevennumbersofprotonsand/orneutronsareunstable.Thisinstabilityincreaseswithatomicnumber,resultingfromthegrowingrepulsionbetw

5、eenincreasingnumbersofprotons.Whenanunstableisotopedecaysitgivesoffradiationknownasradioactivity.Thiscanbeinoneofthreeformsasthistableshows.(Seeinginthefollowingtable.P11)8.UsesofisotopesIsotopesareoftenusedastracers.Verysmalltracesofanisotopecanbede

6、tectedandhencefollowedthroughaprogress.biologye.g.32Ptostudynutrientuptakeinplantsmedicinee.g.131Itostudythyroidfunctionindustrye.g.57Fetostudywearandlubricationinenginesgeneratingpowere.g.235Uinfissionreactors;3Hinfusiongeographye.g.57Fetostudyriver

7、flowarchaeologye.g.14Cincarbondating9.Electronicenergylevels,orbitals,andshells:howelectronsarearrangedinatoms.energylevelsAtomicemissionandabsorptionspectratellusthattheelectronsinanatomhavequantizedordefiniteamountsofenergycalledenergylevels.Rememb

8、erthattheenergylevelforanelectronisthesumofitskineticandpotentialenergy.10.orbitalsAnorbitalisaregionofspaceinwhichthereisahighprobabilityoffindinganelectron.Thereisanorbitalassociatedwitheachenergylevel,butrememberthatitonlytellsyouaboutthepositiono