《基础化学》英文教学课件：chapter-9

Chapter9.StructureofAtomsandPeriodicTableoftheElements§9-1.Fundamentals§9-2.StructureofHydrogenAtom§9-3.QuantumNumbersandAtomicOrbitals§9-4.ElectronConfigurationsandPeriodicityChapter9.StructureofAtomsHowaretheelectronsdistributedinthisspace?whataretheelectronsdoingintheatom?Howaretheelectronsdistribu§1.FundamentalsAllmatteriscomposedof

indivisible

atoms.Anatomisanextremelysmallparticleofmatterthatretainsitsidentityduringchemicalreactions.PostulatesofDalton’satomictheory(1803)FeonCu(111)XeonNi(110)Singleatomscanbevisualizedandmanipulatedbyscanning-tunnelingmicroscope(STM,扫描隧道显微镜).§1.FundamentalsAllmatteri§1.FundamentalsAnelementisatypeofmattercomposedofonlyonekindofatom,eachatomofagivenkindhavingthesameproperties.Na,Cl2.Acompoundisatypeofmattercomposedofatomsoftwoormoreelementschemicallycombinedinfixedproportions.NaCl,H2O.Achemicalreactionconsistsoftherearrangementoftheatomspresentinthereactantstogivenewchemicalcombinationspresentintheproducts.Atomsarenotcreated,destroyed,orbrokenintosmallerparticlesbyanychemicalreaction.§1.FundamentalsAnelementiJohnDalton约翰·道尔顿(1766-1844)England

atomictheory§1.FundamentalsJohnDaltonatomictheory§1.F§1.FundamentalsJ.J.Thomson(1856–1940)English约瑟夫·汤姆逊NobelPrize(Physics),1906Raisinbreadmodel(1904)In1897,Thomsondiscoveredelectrons,bywhichheproposedtheraisinbreadmodel(葡萄干面包模型)

ofatoms.Discoveryofelectron§1.FundamentalsJ.J.ThomsonRMarieCurie

玛丽·居里(1867-1934)Poland

NobelPrize(Physics),1903(Chemistry),1911polonium,Po,84radium,Ra,88

HenriBecquerel亨利·贝克勒尔(1852-1908)France

NobelPrize(Physics),1903DiscoveryofRadioactivityuranium,U,92

§1.FundamentalsMarieCuriepolonium,Po,84HeWilliamThomson,1stBaronKelvin威廉·汤姆森，第一代开尔文男爵(1824–1907)

British

热力学之父WilliamThomson,1stBaronKelvin威廉·汤姆森，第一代开尔文男爵(1824–1907)

British

热力学之父E.Rutherford欧内斯特·卢瑟福(1871–1937)NewZealand

NobelPrize,1908ChemistryDiscoveryofprotonFatherofnuclearphysics§1.FundamentalsWilliamThomson,1stBaronKel§1.Fundamentals§1.Fundamentals§1.FundamentalsAnatomconsistsoftwokindsofparticles:apositively(+)-chargednucleus(10-15m),whichcontainsmost(>99.95%)oftheatom’smass,andoneormoreelectrons.Anelectronisanegatively(-)-chargedparticlethatexistsintheregion(10-10m)aroundthenucleus.Nuclearmodel(有核模型)(1911)§1.FundamentalsAnatomconsis§1.FundamentalsStructureofanatom?Howaretheelectronsdistributedinthisspace?(Whataretheelectronsdoingintheatom?)AccordingtoRutherford’smodel,anatomconsistsofanucleusmanytimessmallerthantheatomitself,withelectronsoccupyingtheremainingspace.§1.FundamentalsStructureofaRutherford’smodelposedadilemma.Accordingtothenuclearmodel,anelectronwouldcontinuouslyloseenergyaselectromagneticradiation(photons);spiralintothenucleus(inabout10-10s).§2.StructureofHydrogenAtomcontinuousenergy:continuouswavelength:continuousspectrum;theatomwould“die”.Rutherford’smodelposedadil§2.StructureofHydrogenAtomI.Continuousvs.linespectrum(连续光谱和线状光谱)Dispersionofwhitelightbyaprism(棱镜):

Whitelight,enteringattheleft,strikesaprism,whichdispersesthelightintoacontinuousspectrumofwavelength.Aheatedsolid(suchasaheatedtungstenfilament(钨丝))emitslightwithcontinuousspectrum(aspectrumcontaininglightofallwavelengths).§2.StructureofHydrogenAtom§2.StructureofHydrogenAtomEmissionlinespectraofsomeelements:Thelinescorrespondstovisiblelight(380~780nm)emittedbyatoms.Aheatedgas(atom)emitslightwithlinespectrum(aspectrumshowingonlycertaincolorsorspecificwavelengthsoflight).HydrogenlinespectraHeliumlinespectra§2.StructureofHydrogenAtom§2.StructureofHydrogenAtom§2.StructureofHydrogenAtom§2.StructureofHydrogenAtomIn1885J.J.Balmershowedthatthewavelengthsinthevisiblespectrumofhydrogencouldbereproducedbyasimpleformula:Herenissomewholenumber(integer)greaterthan2.Thewavelengthsofthefourlinesinthehydrogenatomvisiblespectrumcorrespondton=3,4,5,and6,respectively.§2.StructureofHydrogenAtomMaxPlanck马克斯·普朗克(1858－1947)GermanNobelprize,1918PhysicsPlanckpostulateJosiahWillardGibbs威拉德·吉布斯(1839－1903)USAGibbsentropy§2.StructureofHydrogenAtomMaxPlanckPlanckpostulateJoE=nhν§2.StructureofHydrogenAtomE=nhν§2.StructureofHydroAlbertEinstein

阿尔伯特·爱因斯坦(1879-1955)Nobelprize,1929PhysicsPhotoelectriceffect§2.StructureofHydrogenAtomAlbertEinsteinPhotoelectricConsiderthisanalogytohelpseewhylightofinsufficientenergycannotfreeanelectronfromametalsurface.IfonePing-Pongballdoesnothaveenoughenergytoknockabookoffitsshelf,neitherdoesaseriesofPing-Pongballs,becausethebookcannotsaveuptheenergyfromtheindividualimpacts.Butonebase-balltravelingatthesamespeeddoeshaveenoughenergytomovethebook.Whereastheenergyofaballisrelatedtoitsmassandvelocity,theenergyofaphotonisrelatedtoitsfrequency.Considerthisanalogytohelp§2.StructureofHydrogenAtomII.TheBohrTheoryoftheHydrogenAtom(1913)Toaccountfor:Thestabilityofthehydrogenatom(thattheatomexistsandtheelectrondoesnotcontinuouslyradiateenergyandspiralintothenucleus);Thelinespectrumoftheatom.N.Bohr尼尔斯·玻尔(1885-1962)DenmarkNobelprize(1922)BohrmodelN.Bohr尼尔斯·玻尔(1885-1962)DenmarkNobelprize(1922)§2.StructureofHydrogenAtom§2.StructureofHydrogenAtom1.Energy-levelpostulate:Anelectroncanhaveonlyspecificenergyvaluesinanatom,whicharecalleditsenergylevels(能级).http://www.groundstate(基态)excitedstates(激发态)n:principalquantumnumber(主量子数)§2.StructureofHydrogenAtom§2.StructureofHydrogenAtomTheenergieshavenegativevaluesbecausetheenergyoftheseparatednucleusandelectronistakentobezero.Asthenucleusandelectroncometogethertoformastablestateoftheatom,energyisreleasedandtheenergybecomeslessthanzero,ornegative.Thefirstpostulateexplainsthestabilityofhydrogenatoms.§2.StructureofHydrogenAtom§2.StructureofHydrogenAtom§2.StructureofHydrogenAtom§2.StructureofHydrogenAtom2.Transitions(跃迁)betweenenergylevels:Anelectroninanatomcanchangeenergyonlybygoingfromoneenergyleveltoanotherenergylevel.Bydoingso,theelectronundergoesatransition.Thesecondpostulateexplainsthelinespectrumemittedbyhydrogenatoms.§2.StructureofHydrogenAtom§2.StructureofHydrogenAtomExplainingthelinespectrumemissionbyatomsAnelectroninahigherenergylevel(initialenergylevelEi)undergoesatransitiontoalowerenergylevel(finallevelEf).§2.StructureofHydrogenAtom§2.StructureofHydrogenAtomExample9-1:Whatisthewavelengthoflightemittedwhentheelectroninahydrogenatomundergoesatransitionfromenergyleveln=4toleveln=2?Solution:(blue-green)§2.StructureofHydrogenAtom§2.StructureofHydrogenAtomBalmerseries

(visible):Paschenseries

(infrared):Lymanseries

(ultraviolet):§2.StructureofHydrogenAtom§2.StructureofHydrogenAtom§2.StructureofHydrogenAtomThenucleusiscomposedoftwodifferentkindofparticles,protons(质子),andneutrons(中子).Nuclearcomposition(1932)SubatomicParticles§2.StructureofHydrogenAtomJ.Chadwick詹姆斯·查德威克(1891–1974)NobelPrize,1935PhysicsDiscoveryoftheneutronThenucleusiscomposedoftwo§2.StructureofHydrogenAtomEvaluationofBohr’stheorySuccess:Thetheoryfirmlyestablishedtheconceptofatomicenergylevel.Itcanaccountfor(1)thestabilityofthehydrogenatomand(2)thelinespectrumoftheatom.Limitation:Thetheorywasunsuccessful,however,inaccountingforthedetailsofatomicstructureandinpredictingenergylevelsforatomsotherthanhydrogen.§2.StructureofHydrogenAtom§2.StructureofHydrogenAtomIII.Wave-particleduality(波粒二象性)oftheelectronAccordingtoEinstein,lighthasnotonlywaveproperties,whichwecharacterizebyfrequencyandwavelength,butalsoparticleproperties.Forexample,aparticleoflight,photon,hasmomentum.Thismomentum,mc,isrelatedtothewavelengthofthelight:Relativisticmass§2.StructureofHydrogenAtom§2.StructureofHydrogenAtomDeBroglierelation:LouisdeBrogliereasonedthatiflight(consideredasawave)exhibitsparticleaspects,thenperhapsparticlesofmattershowcharacteristicsofwavesunderthepropercircumstances.Hethereforepostulatedthataparticleofmatterofmassmandspeedhasawavelength,byanalogywithlight:L.deBroglie路易·维克多·德布罗意(1892-1987)FranceNobelprize(1929)Wavenatureofelectrons§2.StructureofHydrogenAtom§2.StructureofHydrogenAtomDeBroglierelation:Anelectron(9.1×10-31kg)movingatabout5.9×105m·s-1hasawavelengthofabout1.2×10-9m.Abasketball(0.60kg)movingatabout10

m·s-1hasawavelengthofabout10-34m.§2.StructureofHydrogenAtom§2.StructureofHydrogenAtom§2.StructureofHydrogenAtom§2.StructureofHydrogenAtomTheyshowedthatelectronsgaveadiffractionpattern(衍射图)

whenreflectedfromacrystalorpassthroughaverythingoldfoil.BothThomsonreceivedNobelprizes:J.J.forshowingthattheelectronisaparticleandG.P.forshowingthatitisawave.ThewavepropertyofelectronswasdemonstratedbyC.Davisson,L.H.GermerandG.P.Thomson(sonofJ.J.Thomson).§2.StructureofHydrogenAtomErnstRuska恩斯特·鲁斯卡(1906–1988)GermanNobelPrize,(1986)PhysicsElectronMicroscopyE.Ruskausedthiswavepropertytoconstructthefirstelectronmicroscope(电子显微镜)

in1933.Shownisthescanningelectronmicroscopeimageofawasp’shead.§2.StructureofHydrogenAtomErnstRuskaElectronMicroscopy§2.StructureofHydrogenAtomYoucannotsaythattheelectronwilldefinitelybeataparticularpositionatagiventime,wecansaythattheelectronislikelytobeatthispoint.Wavepropertyofelectrons:Statisticalstatementsaboutwherewewouldfindtheelectron(probabilityoffindinganelectronatacertainpointinanatom).§2.StructureofHydrogenAtom§2.StructureofHydrogenAtomDeBroglierelationsaysthatelectronscannotbetreatedonlyasparticles.Insomecircumstances,theydemonstratewaveproperties,whichmustbeconsideredtouncovertheatomicstructures.SignificanceofdeBroglierelation§2.StructureofHydrogenAtomIV.UncertaintyPrinciple§2.StructureofHydrogenAtomItisimpossibletoknowsimultaneously,withabsoluteprecision,boththepositionandthemomentumofaparticlesuchasanelectron.W.Heisenberg维尔纳·海森伯(1901-1976)GermanyNobelprize(1932)UncertaintyPrincipleIV.UncertaintyPrinciple§2.S§2.StructureofHydrogenAtomHeisenberg’suncertaintyprinciple(测不准原理):

TheproductoftheuncertaintyinpositionandtheuncertaintyinmomentumofaparticlecanbenosmallerthanPlank’sconstantdividedby4.

x:Theuncertaintyinthexcoordinateofaparticle;px:Theuncertaintyinthemomentuminthexdirection.Ifyouknowverywellwhereaparticleis,youcannotknowwhereitisgoing!§2.StructureofHydrogenAtom§2.StructureofHydrogenAtomForanelectronwithavelocityof6.0×106m·s-1(anerrorof±1%):Forabasketballwithavelocityof10m·s-1(anerrorof±1%)Theuncertaintyprincipleisonlysignificantforparticlesofverysmallmasssuchaselectrons.§2.StructureofHydrogenAtom§2.StructureofHydrogenAtomHeisenberg’suncertaintyprinciplesaysthat,forelectrons,theuncertaintiesinpositionandmomentumarenormallyquitelarge.Wecannotdescribetheelectroninanatomasmovinginadefiniteorbit.Significanceofuncertaintyprinciple§2.StructureofHydrogenAtomV.WaveFunction（波函数）§2.StructureofHydrogenAtomIn1926,E.Schrödingerdevisedatheory(Schrödingerequation)thatcouldbeusedtofindthewavepropertiesofelectronsinatomsandmolecules.E.Schrödinger埃尔文·薛定谔(1887-1961)AustriaNobelprize(1933)Debroglie’srelationappliesquantitativelyonlytoparticlesinaforce-freeenvironment.Itcannotbeapplieddirectlytoanelectroninanatom,wheretheelectronissubjecttotheattractiveforceofthenucleus.SchrödingerequationV.WaveFunction（波函数）§2.Struc§2.StructureofHydrogenAtom§2.StructureofHydrogenAtom§2.StructureofHydrogenAtomInformationaboutanelectroninanatomiscontainedinamathematicalexpressioncalledwavefunction,denotedbytheGreekletter,.ThewavefunctionisobtainedbysolvingSchrödingerequation:2,givestheprobabilityoffindinganelectronwithinaregionofspace.Thediagramshowstheprobabilitydensity(概率密度)(atapoint)foranelectroninahydrogenatominthegroundstate.§2.StructureofHydrogenAtom§2.StructureofHydrogenAtom§2.StructureofHydrogenAtom§2.StructureofHydrogenAtom§2.StructureofHydrogenAtom§2.StructureofHydrogenAtomThegraphshowstheprobability(概率)(withinasphericalshell)offindingtheelectronwithinshellsatvariousdistancesfromthenucleus.Thecurveexhibitsamaximum(r=52.9pm,Bohrradius),whichmeansthattheradialprobabilityisgreatestforagivendistancefromthenucleus.Probability§2.StructureofHydrogenAtom§2.StructureofHydrogenAtomInformationaboutanelectroninanatomiscontainedinawavefunction,whichcanjustbeobtainedbysolvingmeunderspecificconditions.Solveme,andyougeteverythingthestatesofelectronsinanatom.SignificanceofSchrödingerEquation§2.StructureofHydrogenAtom§3.QuantumNumbersandAtomicOrbitalsInformationaboutanelectroninanatomiscontainedinawavefunction,,whichgivestheprobabilityoffindingtheelectronatvariouspointsinspace.Threedifferentquantumnumbersareneededbecausetherearethreedimensionstospace.AgroupofwavefunctionsisobtainedbysolvingSchrödingerequation.Forsolving

Schrödingerequation,

threeintegralconditionsmustbesatisfied.Theseintegersn,l,marereferredas

quantumnumbers.(n,l,m)

specifyawavefunction,n,l,m.§3.QuantumNumbersandAtomic§3.QuantumNumbersandAtomicOrbitalsAwavefunctionforanelectroninanatomiscalledanatomicorbital(原子轨道).Probabilitydensityforanelectroninahydrogenatominthegroundstate.Anatomicorbitalispicturedqualitativelybydescribingtheregionofspacewherethereishighprobability(99%)offindingtheelectrons.Theatomicorbitalsopicturedhasadefiniteshape.§3.QuantumNumbersandAtomicI.Quantumnumbers§3.QuantumNumbersandAtomicOrbitals1.Principalquantumnumber(n，主量子数)Thesmallernis,thelowertheenergy.Inthecaseofthehydrogenatom(singleelectron),nistheonlyquantumnumberdeterminingtheenergy.Forotheratoms,theenergyalsodependstoaslightextentonthelquantumnumber.Generalmeaning:Thisquantumnumberistheoneonwhichthe

energy

ofanelectroninanatomprincipallydepends;itcanhaveany

positiveintegervalue:1,2,3,andsoon.I.Quantumnumbers§3.Quantum§3.QuantumNumbersandAtomicOrbitalsnalsodeterminesthe

averagedistance

ofelectrontothenucleusorthesizeofanorbital.Thelargerthevalueofnis,thelargertheorbital,orthefarerthedistanceofanelectrontothenucleus.Orbitalsofthesamequantumstatenaresaidtobelongtothesame

shell(层).

Shellsaresometimesdesignatedbythefollowingletters:Letter K L M N O P Qn 1 2 3 4 5 6 7§3.QuantumNumbersandAtomic§3.QuantumNumbersandAtomicOrbitals2.Angularmomentumquantumnumber(l,角动量量子数)Thisquantumnumberdistinguishorbitalsofgivennhavingdifferent

shapes,itcanhave

anyintegervaluefrom0ton-1.

n=1:l=0n=2:l=0,1n=3:l=0,1,2n=4:l=0,1,2,3§3.QuantumNumbersandAtomic§3.QuantumNumbersandAtomicOrbitalsLetter s p d fl 0 1 2 3Orbitalsofthesamenbutdifferentlaresaidtobelongtodifferentsubshells(亚层)

ofagivenshell.Thedifferentsubshellsareusuallydenotedbylettersasfollows:Thechoiceoflettersymbolsforquantumnumberssurvivesfromoldspectroscopicterminology(describingthelinesinaspectrumassharp,principal,diffuse,andfundamental).§3.QuantumNumbersandAtomic§3.QuantumNumbersandAtomicOrbitalsTodenoteasubshellwithinaparticularshell,wewritethevalueofthenfortheshell,followedbytheletterdesignationforthesubshell.Forexample,2pdenotesasubshellwithquantumnumbersn=2andl=1.Theenergyofanorbitalalsodependssomewhatonthelquantumnumber(exceptfortheHatom).Foragivenn,theenergyofanorbitalincreaseswithl.3d?4f?energy(n,l)§3.QuantumNumbersandAtomic

Withineachshellofquantumnumbern,therearendifferentkindsoforbitals,eachwithadistinctiveshapedenotedbyanlquantumnumber.§3.QuantumNumbersandAtomicOrbitalsn=1:l=0(s);1s.n=2:l=0(s),1(p);2s,2p.n=3:l=0(s),1(p),2(d); 3s,3p,3d.Withineachshellofquantum§3.QuantumNumbersandAtomicOrbitals3.Magneticquantumnumber(m,磁量子数)Thisquantumnumberdistinguishorbitalsofgivennandl—thatis,ofgivenenergyandshapebuthavinga

differentorientationinspace;theallowed

valuesaretheintegersfrom–ltol.Everyvaluedenotesanindividualatomicorbital.l=0(s):m=0;Thereisonlyoneorbitalinthessubshell.§3.QuantumNumbersandAtomic§3.QuantumNumbersandAtomicOrbitalsl=1(p):m=-1,0,1;Therearethreedifferentorbitalsinthepsubshell.l=2(d):m=-2,-1,0,1,2;

Therearefivedifferentorbitalsinthedsubshell.Thereisnodirectrelationbetweenthevaluesofmandthex,y,zdesignationoftheorbitals.§3.QuantumNumbersandAtomic§3.QuantumNumbersandAtomicOrbitalsNotethatthereare2l+1orbitalsineachsubshellsofquantumnumberl.Theseorbitalshavethesameshapeandenergy,thoughwithdifferentorientationinspace,thuscalledequivalentorbital(等价轨道).§3.QuantumNumbersandAtomic§3.QuantumNumbersandAtomicOrbitals4.Spinquantumnumber(ms,自旋量子数)Thisquantumnumberreferstothe

twopossibleorientationofthespinaxisofanelectron;

possiblevaluesare+1/2and–1/2.

§3.QuantumNumbersandAtomic§3.QuantumNumbersandAtomicOrbitalsThefirstthreequantumnumberscharacterizetheorbitalthatdescribetheregionofspacewhereanelectronismostlikelytobefound;wesaythattheelectron“occupies”thisorbital.Thespinquantumnumberdescribesthespinorientationoftheelectron.Eachelectroninanatomhasfourdifferentquantumnumbers—theprincipalquantumnumber(n),theangularmomentumquantumnumber(l),andthemagneticquantumnumber(m),thespinquantumnumber(ms).§3.QuantumNumbersandAtomic§3.QuantumNumbersandAtomicOrbitals§3.QuantumNumbersandAtomic§3.QuantumNumbersandAtomicOrbitalsPermissibleValuesofQuantumNumbersforAtomicOrbitals§3.QuantumNumbersandAtomic§3.QuantumNumbersandAtomicOrbitalsExample9-2:Statewhethereachofthefollowingsetsofquantumnumbersispermissibleforanelectroninanatom.Ifasetisnotpermissible,explainwhy.Solution:a.n=1,l=1,m=0,ms=b.n=3,l=1,m=-2,ms=c.n=2,l=1,m=0,ms=d.n=2,l=0,m=0,ms=1Notpermissible.Thelisequalton;itmustbelessthann.Notpermissible.Themagnitudeofthem(thatis,themvalue,ignoringitsign)mustnotbegreaterthanl.Permissible.Notpermissible.Themscanbeonly+1/2or–1/2.§3.QuantumNumbersandAtomic§3.QuantumNumbersandAtomicOrbitalsTheelectronina2sorbitalislikelytobefoundintworegions,onenearthenucleusandtheotherinasphericalshellaboutthenucleus(theelectronismostlikelytobehere).II.AtomicorbitalshapesCrosssectionalrepresentationsandcutawaydiagramsoftheprobabilitydistributionsofa1sand2sorbital.§3.QuantumNumbersandAtomic§4.ElectronConfigurationsandPeriodicityI.OrbitalenergiesTheenergyofanorbitaldependsonlyonthequantumnumbersnandl.

Foragivenl,thesmallernis,thelowertheenergy.Foragivenn,theenergyofanorbitalincreaseswithl.Interleaving(能级)交错.1s,2s,2p,3s,3p,4s,3d,4p,5s,4d,5p,6s,4f,5d,7s,5f.§4.ElectronConfigurationsan§4.ElectronConfigurationsandPeriodicityTheorderoforbitalenergy(asinducedfromspectroscopicmeasurements)isshownontherightmnemonicdiagram.DiagonalruleWritethesubshell(s)inrows,eachrowhavingsubshell(s)ofgivenn.Withineachrow,arrangethesubshell(s)byincreasingl.Startingwiththe1ssubshell,drawaseriesofdiagonals(对角线),asshown.§4.ElectronConfigurationsan§4.ElectronConfigurationsandPeriodicityII.ElectronconfigurationsandorbitaldiagramsThenotationforaconfigurationliststhesubshell

symbols,oneaftertheother,withasuperscriptgivingthenumberofelectronsinthatsubshell.1s22s22p1An

electronconfiguration(电子组态)

ofanatomisaparticulardistributionofelectronsamongavailablesubshells.Forexample,theelectronconfigurationofBoron(B),is§4.ElectronConfigurationsan§4.ElectronConfigurationsandPeriodicityAnorbitalisrepresentedbyacircle.Eachgroupoforbitalinasubshellislabeledbyitssubshellnotation.Anelectroninanorbitalisshownbyanarrow;thearrowpointsupwhenms=+1/2anddownwhenms=-1/2.1s2s2pAn

orbitaldiagram(轨道图)

istoshowhowtheorbitalsofsubshellareoccupiedbyelectrons.Forexample,theorbitaldiagramofboronis:§4.ElectronConfigurationsan§4.ElectronConfigurationsandPeriodicity1.Pauliexclusionprinciple(Pauli不相容原理):

Notwoelectronsinanatomcanhavethesamefourquantumnumbers.（1925年）III.Ground-stateelectronconfigurations1sYoucannotplacetwoelectronswiththesamevalueofmsinanorbital.WolfgangPauli(1900-1958)AustriaNobelprize,Physics(1945)§4.ElectronConfigurationsan§4.ElectronConfigurationsandPeriodicityPauliexclusionprinciple:Anorbitalcanholdatmosttwoelectrons,andthenonlyiftheelectronshaveoppositespins.Becausethereonlytwopossiblevaluesofms,anorbitalcanholdnomorethantwoelectrons—andthenonlyifthetwoelectronshavedifferentspinquantumnumbers.Eachsubshellholdsamaximumoftwiceasmanyelectronsasthenumberoforbitalsinthesubshell.§4.ElectronConfigurationsan§4.ElectronConfigurationsandPeriodicityEachshellholdsamaximumoftwiceasmanyelectronsasthenumberoforbitalsintheshell.281832§4.ElectronConfigurationsan§4.ElectronConfigurationsandPeriodicity1s2s2p1s2s2p1s2s2p1s2s2p1s32s11s22s12p71s22s22p63s23p63d84s2Example9-3:

Whichoftheorbitaldiagramsorelectronconfigurationsarepossibleandwhichareimpossible,accordingtothePauliexclusionprinciple?Explain.§4.ElectronConfigurationsan§4.ElectronConfigurationsandPeriodicity2.Build-upprinciple(构造原理):Thisorderreproducesmostoftheexperimentallydeterminedelectronconfigurations.Aschemeusedtoreproducetheelectronconfigurationsofthegroundstatesofatomsbysuccessivelyfillingsubshellswithelectronsinaspecificorder(orderoforbitalenergy,orbuild-uporder).§4.ElectronConfigurationsan§4.ElectronConfigurationsandPeriodicityHydrogen(H,Z=1)Carbon(C,Z=6)Chlorine(Cl,Z=17)Neon(Ne,Z=10)Sodium(Na,Z=11)1s22s22p63s23p64s1Calcium(Ca,Z=20)Iron(Fe,Z=26)1s22s22p63s23p63d64s2Fe2+1s11s22s22p21s22s22p61s22s22p63s11s22s22p63s23p5Potassium(K,Z=19)1s22s22p63s23p64s21s22s22p63s23p64s23d6

1s22s22p63s23p63d6§4.ElectronConfigurationsan§4.ElectronConfigurationsandPeriodicity3.Hund’srule(Hund规则):

Thelowest-energyarrangementofelectronsinasubshellisobtainedbyputtingelectronsintoseparateorbitalsofthesubshellwiththesamespinbeforepairingelectrons.1s2s2p1s2s2p1s2s2pCO1s2s2p1s2s2pFriedrichHund(1896-1997)Germany§4.ElectronConfigurationsan§4.ElectronConfigurationsandPeriodicityOrbitaldiagramsforthegroundstatesofatoms(Z=1~10)§4.ElectronConfigurationsan§4.ElectronConfigurationsandPeriodicityExample9-4:Writetheorbitaldiagramforthegroundstateoftheironatom.Solution:Theelectronconfigurationoftheironatomis1s22s22p63s23p6

3d64s2.Allthesubshellsexceptthe3darefilled.1s2s2p3s3p3d4sForpartiallyfilled3dsubshell,applyHund’srule,puttingfirstfiveelectronsintofiveseparateorbitalswiththesamespin.Thesixthelectronmustdoublyoccupya3dorbital.Theorbitaldiagramis:1s2s2p3s3p3d4s§4.ElectronConfigurationsan§4.ElectronConfigurationsandPeriodicityExceptionstothebuild-upprinciplesCopper(Cu,Z=29)1s22s22p63s23p63d104s1Thehalf-completesubshellconfigurationd5andthecompletesubshellconfigurationd10turnoutexperimentallytohavealowerenergy.Chromium(Cr,Z=24)1s22s22p63s23p63d94s21s22s22p63s23p63d54s11s22s22p63s23p63d44s2§4.ElectronConfigurationsan§4.ElectronConfigurationsandPeriodicityValenceelectron(价电子)Usingtheabb