ChemicalBonding化学链接ppt课件.ppt

1,7,ChemicalBonding化学键结,2,ChapterGoals,1.LewisDotFormulasofAtoms路易斯电子点结构式IonicBonding离子键结2.FormationofIonicCompounds形成离子化合物CovalentBonding共价键结3.FormationofCovalentBonds形成共价键4.BondLengthsandBondEnergies键长及键能5.LewisFormulasforMoleculesandPolyatomicIons分子极多元子离子之路易斯结构式6.WritingLewisFormulas:TheOctetRule八隅体法则7.FormalCharges形式电荷8.WritingLewisFormulas:LimitationsoftheOctetRule八隅体法则之限制9.Resonance共振10.PolarandNonpolarCovalentBonds极性及非极性共价键结11.DipoleMoments偶极距12.TheContinuousRangeofBondingTypes键结形式之连续范围,3,Introduction,Attractiveforcesthatholdatomstogetherincompoundsarecalledchemicalbonds(化合物中将原子拉进的吸引力称之为化学键结)Theelectronsinvolvedinbondingareusuallythoseintheoutermost(valence)shell(与键结有关的电子通常是指最外层的电子),4,Introduction,Chemicalbondsareclassifiedintotwotypes:Ionicbonding离子键结resultsfromelectrostaticattractionsamongions,whichareformedbythetransferofoneormoreelectronsfromoneatomtoanother.离子键为阳离子与阴离子间之库伦静电力，阳离子由金属失去电子形成，阴离子由非金属得到电子形成。两正负电荷之离子吸引力，称为离子键。Ioniccompound离子化合物NaClCovalentbonding共价键结resultsfromsharingoneormoreelectronpairsbetweentwoatoms.价键为两原子共享电子对之化学键，其结合原子皆为非金属原子CovalentcompoundH2,Cl2,5,6,LewisDotFormulasofAtoms原子的路易斯电子点结构式,LewisdotformulasorLewisdotrepresentationsareaconvenientbookkeepingmethodfortrackingvalenceelectrons价电子.Theelectronsintheoutermostoccupiedshells(最外层的电子数)sandporbitalsValenceelectronsarethoseelectronsthataretransferredorinvolvedinchemicalbonding(价电子是指与化学键结有关或转移的电子)Theyarechemicallyimportant,7,LewisDotFormulas路易斯结构ofAtoms,ElementsthatareinthesameperiodicgrouphavethesameLewisdotstructures(同族元素具相同路易斯结构),1electroninvalenceshell,5electronsinvalenceshell,Notasusefulforthetransitionandinnertransitionelements(不适用于过渡元素),8,IonicBonding离子键结,FormationofIonicCompounds形成离子化合物Anionisanatomoragroupofatomspossessinganetelectricalcharge.Ionscomeintwobasictypes:positive(+)ionsorcationsTheseatomshavelost1ormoreelectrons.negative(-)ionsoranionsTheseatomshavegained1ormoreelectrons.,9,FormationofIonicCompounds,Monatomicionsconsistofoneatom.Examples:Na+sodiumion,Ca2+,Al3+-cationsCl-chlorideion,O2-,N3-anionsPolyatomicionscontainmorethanoneatom.Examples:NH4+ammoniumion-cationNO2-,CO32-,SO42-sulfateionanionsTheatomsofapolyatomicionareheldtogetherbycovalentbonds(多原子离子之原子间以共价键结),10,Elementsthathavelowelectronegativitiesandlowionizationenengymetals(oxidozed;loseelectronstoformcations)Elementsthathavehighelectronegativitiesandverynegativeelectronaffinitiesnonmetals(reduced;gainelectronstoformanions),IonicBondingistheattractionofoppositelychargedions(cationsandanions)inlargenumberstoformasolid.Suchasolidcompoundiscalledanionicsolid.,React,Ioniccompound,11,FormationofIonicCompounds,ReactionofGroupIAMetalswithGroupVIIANonmetals,1Ametal7Anonmetal2Li(s)+F2(g)2LiF(s)SilveryellowwhitesolidSolidgaswithan842oCmeltingpoint,12,FormationofIonicCompounds,TheunderlyingreasonfortheformationofLiFliesintheelectronconfigurationsofLiandF.1s2s2pLiFTheseatomsformionswiththeseconfigurations.Li+sameconfigurationasHelossoneelectronF-sameconfigurationasNegainedoneelectron,Li+isoelectronicwithHe,等电子离子,F+isoelectronicwithNe,13,FormationofIonicCompounds,WecanalsouseLewisdotformulastorepresenttheneutralatomsandtheionstheyform.,14,FormationofIonicCompounds,TheLi+ioncontainstwoelectrons,sameastheheliumatom.Li+ionsareisoelectronic等电子离子withhelium.TheF-ioncontainstenelectrons,sameastheneonatom.F-ionsareisoelectronicwithneon.Isoelectronicspeciescontainthesamenumberofelectrons.Mostioniccompoundsformedbyreactionsbetweenrepresentativemetals典型金属andrepresentativenonmetals典型非金属,15,FormationofIonicCompounds,ThereactionofpotassiumwithbromineisasecondexampleofagroupIAmetalwithaGroupVIIAnonmetal.Writethereactionequation.,1Ametal7Anonmetal2K(s)+Br2(g)2KBr(s)ionicsolid,16,FormationofIonicCompounds,WelookattheelectronicstructuresofKandBr.4s4pKArBrArandthedelectronsTheatomsformionswiththeseelectronicstructures.4s4pK+sameconfigurationasArBr-sameconfigurationasKr,17,FormationofIonicCompounds,WritetheLewisdotformularepresentationforthereactionofKandBr.,18,FormationofIonicCompounds,Thereisageneraltrendevidentintheformationoftheseions.Cationsbecomeisoelectronicwiththeprecedingnoblegas.之前的钝气Anionsbecomeisoelectronicwiththefollowingnoblegas.之后的钝气,19,FormationofIonicCompounds,IngeneralforthereactionofIAmetalsandVIIAnonmetals,thereactionequationis:2M(s)+X22M+X-(s)whereMisthemetalsLitoCsandXisthenonmetalsFtoI.Electronicallythisisoccurring.nsnpnsnpMM+XX-,20,FormationofIonicCompounds,NextweexaminethereactionofIIAmetalswithVIIAnonmetals.Thisreactionformsmostlyioniccompounds.NotableexceptionsareBeCl2,BeBr2,andBeI2whicharecovalentcompounds.OneexampleisthereactionofBeandF2.Be(s)+F2(g)BeF2(g),21,FormationofIonicCompounds,Thevalenceelectronsinthesetwoelementsarereactinginthisfashion.2s2p2s2pBeHeBe2+FHeF-Next,drawtheLewisdotformularepresentationofthisreaction.,22,FormationofIonicCompounds,TheremainderoftheIIAmetalsandVIIAnonmetalsreactsimilarly.Symbolicallythiscanberepresentedas:M(s)+X2M2+X2-McanbeanyofthemetalsBetoBa.XcanbeanyofthenonmetalsFtoCl.,23,FormationofIonicCompounds,ForthereactionofIAmetalswithVIAnonmetals,agoodexampleisthereactionoflithiumwithoxygen.Thereactionequationis:,24,FormationofIonicCompounds,DrawtheelectronicconfigurationsforLi,O,andtheirappropriateions.2s2p2s2pLiHeLi1+OHeO2-DrawtheLewisdotformularepresentationofthisreaction.,25,FormationofIonicCompounds,TheremainderoftheIAmetalsandVIAnonmetalsbehavesimilarly.Symbolicallythiscanberepresentedas:2M(s)+XM21+X-McanbeanyofthemetalsLitoCs.XcanbeanyofthenonmetalsOtoTe.,26,FormationofIonicCompounds,ThereactionofIIAmetalsandVAnonmetalsalsofollowsthetrendsthatwehaveestablishedinthischapter.Thereactionofcalciumwithnitrogenisagoodexample.Thereactionequationis:3Ca(s)+N2(g)Ca3N2(s),27,FormationofIonicCompounds,DrawtheelectronicrepresentationofCa,N,andtheirions.4s4p4s4pCaArCa2+2s2p2s2pNHeN3-DrawtheLewisdotrepresentationofthisreaction.,28,FormationofIonicCompounds,OtherIIAandVAelementsbehavesimilarly.Symbolically,thisreactioncanberepresentedas:3M(s)+2X(g)M32+X23-McanbetheIIAelementsBetoBa.XcanbetheVAelementsNtoAs.,29,FormationofIonicCompounds,d-transitionMetalIonsTheoutermostselectronsandenergylevellowerdelectronsarealwaysthefirstoneslostwhentransitionmetalsformsimpleions.,3d4s3d4sScArSc3+Ar3e-lostZnArZn2+Ar2e-lostMostother3d-transitionmetalscanformatleasttwocationsintheircompounds.3d4s3d4sCoArCo2+Ar2e-lostCoArCo3+Ar3e-lost,钪,30,FormationofIonicCompounds,H,anonmetal,formsioniccompoundswithIAandIIAmetalsforexample,LiH,KH,CaH2,andBaH2.Otherhydrogencompoundsarecovalent.,GroupIAandIIAcanformperoxide(containO22-ion)orsuperoxide(containO2-ion).Theperoxideandsuperoxideionscontainatomsthatarecovalentlybondedtooneanother,3A,31,31,GroupIAandIIAcanformperoxide(containO22-ion)orsuperoxide(containO2-ion).Theperoxideandsuperoxideionscontainatomsthatarecovalentlybondedtooneanother,32,FormationofIonicCompounds,Ioniccompoundsformextendedthreedimensionalarraysofoppositelychargedions.Ioniccompoundshavehighmeltingpointsbecausethecoulombforce库仑力,whichholdsioniccompoundstogether,isstrong.,33,FormationofIonicCompounds,CoulombsLawdescribestheattractionofpositiveionsfornegativeionsduetotheoppositecharges.,34,FormationofIonicCompounds,SmallionswithhighionicchargeshavelargeCoulombicforcesofattraction.LargeionswithsmallionicchargeshavesmallCoulombicforcesofattraction.Usethisinformation,plustheperiodicityrulesfromChapter6,toarrangethesecompoundsinorderofincreasingattractionsamongionsKCl,Al2O3,CaO,35,CovalentBonding共价键结,Covalentbondsareformedwhenatomsshareelectrons.ItOccurswhentheelectronegativitydifferencebetweenelements(atoms)iszeroorrelativitysmall(电负度几乎没差)Thebondsbetweenatomswithinamolecule(intramolecularbonds分子内键结)arerelativelystrong,buttheforceofattractionbetweenmolecules(intermolecularforces分子间键结)arerelativelyweaklowermeltingandboilingpointsthanioniccompound(较离子化合物的熔点及沸点低)Iftheatomsshare2electronsasinglecovalentbondisformed(若原子共享2个电子则形成单一共价键)Iftheatomsshare4electronsadoublecovalentbondisformed(若原子共享4个电子则形成二个共价键)Iftheatomsshare6electronsatriplecovalentbondisformed(若原子共享6个电子则形成三个共价键)TheattractionbetweentheelectronsiselectrostaticinnatureTheatomshavealowerpotentialenergywhenbound.,36,FormationofCovalentBonds,RepresentationoftheformationofanH2moleculefromHatoms.,Theelectronofeachatomisattractedbythepositivelychargednucleusoftheotheratom,sotheelectrondensitybeginstoshift(bluearrows)(电子受到带正电的原子核的吸引,电子团开始变化)Theelectroncloudsofthetwoatomsrepeloneanother,andsodothenucleiofthetwoatoms(Redarrows)(两个原子亦会有排斥力),Thetwo1sorbitalsoverlap,37,FormationofCovalentBonds,ThisfigureshowsthepotentialenergyofanH2moleculeasafunctionofthedistancebetweenthetwoHatoms.,Foranycovalentbondthereisaninternucleardistancewheretheattractiveandrepulsiveforcesbalance.Thisdistanceisthebondlength(彼此间的距离称键长).Theenergydifferenceisthebondenergy(能量的差异称为键能),太靠近,产生斥力,太远,引力太小,无键结,斥力与引力达成平衡,稳定的排列,38,Bonddissociationenergy键离解能Bondenergy键能,39,40,FormationofCovalentBonds,WecanuseLewisdotformulastoshowcovalentbondformation.Hmoleculeformationrepresentation.,2.HFmoleculeformation,H+HH:HorH-H,3.F2moleculeformation,41,H2OHOCO2NH4+N:5electronsH:1electronsTotal9electrons,or,Dotformula,Dashformula线结构式,42,WritingLewisFormulas:TheOctetRule八隅体法则,N-A=SruleSimplemathematicalrelationshiptohelpuswriteLewisdotformulas.N=numberofelectronsneededtoachieveanoblegasconfiguration.(要达到钝气组态的电子数目,通常为8)Nusuallyhasavalueof8forrepresentativeelements.Nhasavalueof2forHatoms.A=numberofelectronsavailableinvalenceshellsoftheatoms.(原子的价电子数)Aisequaltotheperiodicgroupnumberforeachelement.Aisequalto8forthenoblegases.S=numberofelectronssharedinbonds.(形成键结可共享的电子数)A-S=numberofelectronsinunshared,lone,pairs.(不共享的电子数,又称孤电子对),43,LewisFormulasforMoleculesandPolyatomicIons,First,weexploreLewisdotformulasofhomonucleardiatomicmolecules.Twoatomsofthesameelement.Hydrogenmolecule,H2.,2.Fluorine,F2,Nitrogen,N2,H:HorHH,or,or,N=2x8=16e-neededA=2x7=14e-availableS=N-A=2e-shared,N=2x2=4e-neededA=2x1=2e-availableS=N-A=2e-shared,N=2x8=16e-neededA=2x5=10e-availableS=N-A=6e-shared2moleculewith6electrons3covalentbond,44,LewisFormulasforMoleculesandPolyatomicIons,Next,lookatheteronucleardiatomicmolecules.Twoatomsofdifferentelements.Hydrogenhalides卤化氢aregoodexamples.hydrogenfluoride,HF,2.hydrogenchloride,HCl,3.hydrogenbromide,HBr,or,or,or,N=1x2+1x8=10e-neededA=1x1+1x7=8e-availableS=N-A=2e-shared,45,LewisFormulasforMoleculesandPolyatomicIons,Nowwewilllookataseriesofslightlymorecomplicatedheteronuclearmolecules.Water,H2O,or,Ammoniamolecule,NH3,or,N=2x2+1x8=12e-neededA=2x1+1x6=8e-availableS=N-A=4e-shared,N=3x2+1x8=14e-neededA=3x1+1x5=8e-availableS=N-A=6e-shared,46,LewisFormulasforMoleculesandPolyatomicIons,Lewisformulascanalsobedrawnformolecularions.Oneexampleistheammoniumion,NH4+.,NoticethattheatomsotherthanHinthesemoleculeshaveeightelectronsaroundthem.,N=1x8+4x2=16e-need1Catom4HatomA=1x5+4x1-1=8e-available1Catom4Hatom(+1charge)S=N-A=16-8=8e-share,47,AGuildtoWritingLewisFormulas,Selectareasonable(symmetrical)“skeleton”forthemoleculeorpolyatomicion选择最合理分子当作骨架Theleastelectronegativeelementisusuallythecentralelement,excepttheH电负度最小者通常为中心分子,氢除外Carbonbondstotwo,threeorfouratoms,butnevermorethanfour碳可与2,3及4个原子键结Oxygenatomsdonotbondtoeachotherexceptin(氧原子不会键结在一起,除非)O2andO3hydrogenperoxide,H2O2,andtheperoxidecontaintheO22-groupSuperoxide,whichcontaintheO2-groupInternaryoxoacids,hydrogenusuallybondtoanOatom,nottothecentralatom,HNO2三元含氧酸中,氢通常与氧键结Forthosehavemorethanonecentralatom,themostsymmetricalskeletonspossibleareused,suchasC2H4,P2O74-,48,AGuildtoWritingLewisFormulas,2.CalculateN,thenumberofvalenceshellelectronsneededbyallatomsinthemoleculeorirontoachievenoblegasconfigurationsPF3N=1x8(Patom)+3x8(Fatoms)=32e-needCH3OHN=1x8(Catom)+4x2(Hatoms)+1x8(Oatom)=24e-needNO3-N=1x8(Natom)+3x8(Oatoms)=32e-needCalculateA,thenumberofelectronsavailableintheoutershellsofalltheatomsPF3A=1x5(Patom)+3x7(Fatoms)=26e-availableCH3OHA=1x4(Catom)+4x1(Hatoms)+1x6(Oatom)=14e-availableNO3-A=1x5(Natom)+3x6(Oatoms)+1(for1-charge)=24e-available,49,AGuildtoWritingLewisFormulas,CalculateS,totalnumberofelectronssharedinthemoleculeorion,usingtherelationshipS=N-APF3S=N-A=32-26=6e-shared(3pairsofe-shared)CH3OHS=24-14=10e-shared(5pairsofe-shared)NO3-S=32-24=8e-hared(4pairsofe-shared),50,3.PlacetheSelectronintotheskeletonassharedpairs.Usedoubleandtriplebondsonlywhennecessary.,S=6,S=10,S=8,(3pairsofe-shared),(5pairsofe-shared),(4pairsofe-shared),51,4.ChecktheadditionalelectronsintotheskeletonasunsharedpairstofilltheoctetofeveryAgroupelement(exceptH,sharedonly2e-),NO3-,PF3,CH3OH,52,WritingLewisFormulas:TheOctetRule,Theoctetrulestatesthatrepresentativeelementsusuallyattainstablenoblegaselectronconfigurationsinmostoftheircompounds.Lewisdotformulasarebasedontheoctetrule.Weneedtodistinguishbetweenbonding(orshared)electronsandnonbonding(orunsharedorlonepairs)ofelectrons.,53,WritingLewisFormulas:TheOctetRule,Example7-2:WriteLewisdotanddashformulasforhydrogencyanide,HCN.N=2(H)+8(C)+8(N)=18A=1(H)+4(C)+5(N)=10S=8A-S=2Thismoleculehas8electronsinsharedpairsand2electronsinlonepairs.,or,54,WritingLewisFormulas:TheOctetRule,Example7-3:WriteLewisdotanddashformulasforthesulfiteion,SO32-.N=8(S)+3x8(O)=32A=6(S)+3x6(O)+2(-charge)=26S=6A-S=20Thusthispolyatomicionhas6electronsinsharedpairsand20electronsinlonepairs.Whichatomisthecentralatominthision?,55,WritingLewisFormulas:TheOctetRule,Whatkindofcovalentbonds,single,double,ortriple,mustthisionhavesothatthesixsharedelectronsareusedtoattachthethreeOatomstotheSatom?,or,56,Example7-1WritingLewisFormulaWritetheLewisformulaforthenitrogenmolecule,N2,carbondisulfide,CS2andthecarbonateion,CO32-(a)N2(b)CS2(b)CO32-,or,N=2x8=16e-neededA=2x5=10e-availableS=N-A=6e-shared2moleculewith6electrons3covalentbond,N=1x8+2x8=24e-neededA=1x4+2x6=16e-availableS=N-A=8e-shared3moleculewith8electrons2x2covalentbond,or,N=1x8+3x8=32e-neededA=1x4+3x6+2=24e-availableS=N-A=8e-sharedFourpairsareshared,or,Exercise29,30,38,57,hydrocarbon,乙烯,乙炔,乙烷,甲烷,甲醛,氯仿,三氯甲烷,乙醇,酒精,58,FormalCharge形式电荷,CalculationofaformalchargeonamoleculeisamechanismfordeterminingcorrectLewisstructuresTheformalchargeisthehypotheticalchargeonanatominamoleculeorpolyatomicion.ThebestLewisstructureswillhaveformalchargesontheatomsthatarezeroornearlyzero.形式电荷：基于共享电子对由两键结原子平分共享的原则下，此原子的价电子数与在自由原子状态的价电子数两者的差值。,59,FormalCharge,RulesforAssigningFormalChargeFormalCharge=groupnumber(numberofbonds+numberofunsharede-)Anatomthathasthesamenumberofbondsasitsperiodicgroupnumberhasaformalchargeof0.a.Theformalchargesofallatomsmustsumto0inmolecules.b.Theformalchargesmustsumtotheionschargeforapolyatomicion.,形式电荷的定义:(路易斯结构中的)价电子数=孤电子数+键结电子数形式电荷=自由原子的价电子数价电子数=自由原子的价电子数孤电子数键结电子数,60,InNH3Natom:group5A,has3bondsand2unsharede-FC=(groupnumber)(numberofbonds)+(numberofunsharede-)=5-(3+2)=0H:FC=1-(1+0)=0theformalchargeofNandHarebothzeroinNH3,sothesumoftheformalchargedis0+3(0)=0InNH4+theatomhasfourbondsandnosharede-forNFC=5-(4+0)=1forHFC=1-(1+0)=0NH4+=1+4(0)=1,61,FormalCharge,Cl7(2+4)=+1N5(3+2)=0O6(1+6)=-1,Cl7(1+6)=0N5(3+2)=0O6(2+4)=0,Considernitrosylchloride,NOCl,i,ii,(ii)isapreferableLewisformulabecauseithassmallerchargesthan(i),62,WritingLewisFormulas:LimitationsoftheOctetRule,Therearesomemoleculesthatviolate违背theoctetrule.ForthesemoleculestheN-A=Sruledoesnotapply:ThecovalentcompoundsofBe.Use4electronsasNnumberThecovalentcompoundsoftheIIIAGroup.Use6electronsasNnumberSpecieswhichcontainanoddnumberofelectrons,suchasNO2.NOwith11valenceshellelectronsandNO2with17.Speciesinwhichthecentralelementmusthaveashareofmorethan8valenceelectronstoaccommodateallofthesubstituents.Compoundsofthed-andf-transitionmetals.,63,WritingLewisFormulas:LimitationsoftheOctetRule,Inthosecaseswheretheoctetruledoesnotapply,thesubstituentsattachedtothecentralatomnearlyalwaysattainnoblegasconfigurations.Thecentralatomdoesnothaveanoblegasconfigurationbutmayhavefewerthan8(exceptions1,2,&3)ormorethan8(exceptions4&5).,64,Example7-1WritingLewisFormulaWritetheLewisformulafortheberylliumchloride,BeCl2,borontrichloride,BCl3andthephosphoruspentafluoride,PF5(a)BeCl2(b)BCl3(b)PF5,N=2x8+1x4=20e-neededA=2x7+1x2=16e-availableS=N-A=4e-shared,or,N=3x8+1x6=30e-neededA=3x7+1x3=24e-availableS=N-A=6e-shared,or,N=5x8+1x8=48e-neededA=5x7+1x5=40e-availableS=N-A=8e-shared5FbondtoP.Thisrequiresthesharingaminimum10e-.IncreaseSfrom8e-to10e-.,or,65,Example7-1WritingLewisFormulaWritetheLewisformulaforthesulfirtetrafluoride,SF4,thetriiodideion,I3-(a)SF4(b)I3-,N=1x8+4x8=40e-neededA=1x6+4x7=34e-availableS=N-A=6e-sharedRequiresaminimum8e-,N=3x8=24e-neededA=3x7+1x1=22e-availableS=N-A=2e-shared,Exercise62,66,Resonance共振,Resonanceisaflawedmethodofrepresentingmolecules.TherearenosingleordoublebondsinSO3.Infact,allofthebondsinSO3areequivalent.ThebestLewisformulaofSO3thatcanbedrawnis:,共价键结构的混成体,称之为共振,67,ThetypicalC-Osinglebondlengthis1.43ThetypicalC=Odoublebondlengthis1.22TheC-ObondintheCO32-ionisat1.29Delocalizationofbondingelectron非定域电子键,68,PolarandNonpolarCovalentBonds极性及非极性共价键,Covalentbondsinwhichtheelectronsaresharedequallyaredesignatedasnonpolarcovalentbonds.Nonpolarcovalentbondshaveasymmetricalchargedistribution(对称的电荷分布)Tobenonpolarthetwoatomsinvolvedinthebondmustbethesameelementtoshareequally.Someexamplesofnonpolarcovalentbonds.H2N2,69,PolarandNonpolarCovalentBonds,Covalentbondsinwhichtheelectronsareno