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1、Chapter 8Bonding:General ConceptsChapter8QuestionstoConsiderWhatismeantbytheterm“chemicalbond”?Whydoatomsbondwitheachothertoformcompounds?Howdoatomsbondwitheachothertoformcompounds?CopyrightCengageLearning.Allrightsreserved2Section8.1Types of Chemical BondsCopyrightCengageLearning.Allrightsreserved3
2、AChemicalBondNosimple,andyetcomplete,waytodefinethis.Forcesthatholdgroupsofatomstogetherandmakethemfunctionasaunit.Abondwillformiftheenergyoftheaggregateislowerthanthatoftheseparatedatoms.Section8.1Types of Chemical BondsCopyrightCengageLearning.Allrightsreserved4TheInteractionofTwoHydrogenAtomsSect
3、ion8.1Types of Chemical BondsCopyrightCengageLearning.Allrightsreserved5TheInteractionofTwoHydrogenAtomsSection8.1Types of Chemical BondsCopyrightCengageLearning.Allrightsreserved6KeyIdeasinBondingIonicBondingelectronsaretransferredCovalentBondingelectronsaresharedequallybynucleiWhataboutintermediat
4、ecases?Section8.1Types of Chemical BondsCopyrightCengageLearning.Allrightsreserved7PolarCovalentBondUnequalsharingofelectronsbetweenatomsinamolecule.Resultsinachargeseparationinthebond(partialpositiveandpartialnegativecharge).Section8.1Types of Chemical BondsCopyrightCengageLearning.Allrightsreserve
5、d8TheEffectofanElectricFieldonHydrogenFluorideMoleculesindicatesapositiveornegativefractionalcharge.Section8.1Types of Chemical BondsPolarMoleculesCopyrightCengageLearning.Allrightsreserved9Section8.1Types of Chemical BondsCopyrightCengageLearning.Allrightsreserved10Whatismeantbytheterm“chemicalbond
6、?”Whydoatomsbondwitheachothertoformmolecules?Howdoatomsbondwitheachothertoformmolecules?CONCEPT CHECK!CONCEPT CHECK!Section8.2ElectronegativityTheabilityofanatominamoleculetoattractsharedelectronstoitself.ForamoleculeHX,therelativeelectronegativitiesoftheHandXatomsaredeterminedbycomparingthemeasured
7、HXbondenergywiththe“expected”HXbondenergy.CopyrightCengageLearning.Allrightsreserved11Section8.2ElectronegativityOntheperiodictable,electronegativitygenerallyincreasesacrossaperiodanddecreasesdownagroup.Therangeofelectronegativityvaluesisfrom4.0forfluorine(themostelectronegative)to0.7forcesium(thele
8、astelectronegative).CopyrightCengageLearning.Allrightsreserved12Section8.2ElectronegativityThePaulingElectronegativityValuesCopyrightCengageLearning.Allrightsreserved13Section8.2ElectronegativityIflithiumandfluorinereact,whichhasmoreattractionforanelectron?Why?Inabondbetweenfluorineandiodine,whichha
9、smoreattractionforanelectron?Why?CopyrightCengageLearning.Allrightsreserved14CONCEPT CHECK!CONCEPT CHECK!Section8.2ElectronegativityWhatisthegeneraltrendforelectronegativityacrossrowsanddowncolumnsontheperiodictable?Explainthetrend.CopyrightCengageLearning.Allrightsreserved15CONCEPT CHECK!CONCEPT CH
10、ECK!Section8.2ElectronegativityCopyrightCengageLearning.AllrightsreservedSection8.2ElectronegativityArrangethefollowingbondsfrommosttoleastpolar:a) NFOFCFb) CFNOSiFc)ClClBClSCla)CF,NF,OFb) SiF,CF,NOc)BCl,SCl, ClClCopyrightCengageLearning.Allrightsreserved17EXERCISE!EXERCISE!Section8.2Electronegativi
11、tyWhichofthefollowingbondswouldbetheleastpolaryetstillbeconsideredpolarcovalent?MgOCOOOSiONOCopyrightCengageLearning.Allrightsreserved18CONCEPT CHECK!CONCEPT CHECK!Section8.2ElectronegativityWhichofthefollowingbondswouldbethemostpolarwithoutbeingconsideredionic?MgOCOOOSiONOCopyrightCengageLearning.A
12、llrightsreserved19CONCEPT CHECK!CONCEPT CHECK!Section8.3Bond Polarity and Dipole MomentsDipoleMomentPropertyofamoleculewhosechargedistributioncanberepresentedbyacenterofpositivechargeandacenterofnegativecharge.Useanarrowtorepresentadipolemoment.Pointtothenegativechargecenterwiththetailofthearrowindi
13、catingthepositivecenterofcharge.CopyrightCengageLearning.Allrightsreserved20Section8.3Bond Polarity and Dipole MomentsDipoleMoment21Section8.3Bond Polarity and Dipole MomentsNoNetDipoleMoment(DipolesCancel)CopyrightCengageLearning.Allrightsreserved22Section8.4Ions: Electron Configurations and SizesS
14、tableCompoundsAtomsinstablecompoundsusuallyhaveanoblegaselectronconfiguration.CopyrightCengageLearning.Allrightsreserved23Section8.4Ions: Electron Configurations and SizesElectronConfigurationsinStableCompoundsWhentwo nonmetalsreacttoformacovalentbond,theyshareelectronsinawaythatcompletesthevalencee
15、lectronconfigurationsofbothatoms.Whenanonmetal and a representative-group metalreacttoformabinaryioniccompound,theionsformsothatthevalenceelectronconfigurationofthenonmetalachievestheelectronconfigurationofthenextnoblegasatom.Thevalenceorbitalsofthemetalareemptied.CopyrightCengageLearning.Allrightsr
16、eserved24Section8.4Ions: Electron Configurations and SizesIsoelectronicSeriesAseriesofions/atomscontainingthesamenumberofelectrons.O2-,F-,Ne,Na+,Mg2+,andAl3+CopyrightCengageLearning.Allrightsreserved25Section8.4Ions: Electron Configurations and SizesIonicRadiiCopyrightCengageLearning.Allrightsreserv
17、ed26Section8.4Ions: Electron Configurations and SizesChooseanalkalimetal,analkalineearthmetal,anoblegas,andahalogensothattheyconstituteanisoelectronicserieswhenthemetalsandhalogenarewrittenastheirmoststableions.Whatistheelectronconfigurationforeachspecies?Determinethenumberofelectronsforeachspecies.
18、Determinethenumberofprotonsforeachspecies.CopyrightCengageLearning.Allrightsreserved27CONCEPT CHECK!CONCEPT CHECK!Section8.4Ions: Electron Configurations and SizesPeriodicTableAllowsUstoPredictManyPropertiesTrendsfor:Atomicsize,ionradius,ionizationenergy,electronegativityElectronconfigurationsFormul
19、apredictionforioniccompoundsCovalentbondpolarityrankingCopyrightCengageLearning.Allrightsreserved28Section8.5Energy Effects in Binary Ionic CompoundsWhatarethefactorsthatinfluencethestabilityandthestructuresofsolidbinaryioniccompounds?Howstronglytheionsattracteachotherinthesolidstateisindicatedbythe
20、latticeenergy.CopyrightCengageLearning.Allrightsreserved29Section8.5Energy Effects in Binary Ionic CompoundsLatticeEnergyThechangeinenergythattakesplacewhenseparatedgaseousionsarepackedtogethertoformanionicsolid.k=proportionalityconstantQ1andQ2=chargesontheionsr= shortestdistancebetweenthecentersoft
21、hecationsandanionsCopyrightCengageLearning.Allrightsreserved30Section8.5Energy Effects in Binary Ionic CompoundsBorn-HaberCycleforNaCLCopyrightCengageLearning.Allrightsreserved31Section8.5Energy Effects in Binary Ionic CompoundsFormationofanIonicSolid1.Sublimationofthesolidmetal.M(s)M(g)endothermic2
22、. Ionizationofthemetalatoms.M(g)M+(g)+e-endothermic3. Dissociationofthenonmetal.1/2X2(g)X(g)endothermicCopyrightCengageLearning.Allrightsreserved32Section8.5Energy Effects in Binary Ionic CompoundsFormationofanIonicSolid(continued)4Formationofnonmetalionsinthegasphase.X(g)+e-X-(g)exothermic5.Formati
23、onofthesolidioniccompound.M+(g)+X-(g) MX(s)quiteexothermicCopyrightCengageLearning.Allrightsreserved33Section8.5Energy Effects in Binary Ionic CompoundsComparingEnergyChangesSection8.6Partial Ionic Character of Covalent BondsNobondsreach100%ioniccharacterevenwithcompoundsthathavethemaximumpossibleel
24、ectronegativitydifference.CopyrightCengageLearning.Allrightsreserved35Section8.6Partial Ionic Character of Covalent BondsTherelationshipbetweentheioniccharacterofacovalentbondandtheelectronegativitydifferenceofthebondedatomsCopyrightCengageLearning.Allrightsreserved36Section8.6Partial Ionic Characte
25、r of Covalent BondsOperationalDefinitionofIonicCompoundAnycompoundthatconductsanelectriccurrentwhenmeltedwillbeclassifiedasionic.CopyrightCengageLearning.Allrightsreserved37Section8.7The Covalent Chemical Bond: A ModelModelsModelsareattemptstoexplainhownatureoperatesonthemicroscopiclevelbasedonexper
26、iencesinthemacroscopicworld.CopyrightCengageLearning.Allrightsreserved38Section8.7The Covalent Chemical Bond: A ModelFundamentalPropertiesofModels1.Amodeldoesnotequalreality.2.Modelsareoversimplifications,andarethereforeoftenwrong.3.Modelsbecomemorecomplicatedandaremodifiedastheyage.4.Wemustundersta
27、ndtheunderlyingassumptionsinamodelsothatwedontmisuseit.5.Whenamodeliswrong,weoftenlearnmuchmorethanwhenitisright.CopyrightCengageLearning.Allrightsreserved39Section8.8Covalent Bond Energies and Chemical ReactionsBondEnergiesTobreakbonds,energymustbeaddedtothesystem(endothermic,energytermcarriesaposi
28、tivesign).Toformbonds,energyisreleased(exothermic,energytermcarriesanegativesign).CopyrightCengageLearning.Allrightsreserved40Section8.8Covalent Bond Energies and Chemical ReactionsBondEnergiesH=SnD(bonds broken)SnD(bonds formed)Drepresentsthebondenergypermoleof bonds(alwayshasapositivesign).Copyrig
29、htCengageLearning.Allrightsreserved41Section8.8Covalent Bond Energies and Chemical ReactionsPredictDHforthefollowingreaction:Giventhefollowinginformation:Bond Energy (kJ/mol)CH413CN 305CC347891 DH=42kJCopyrightCengageLearning.Allrightsreserved42CONCEPT CHECK!CONCEPT CHECK!Section8.9The Localized Ele
30、ctron Bonding ModelLocalizedElectronModelAmoleculeiscomposedofatomsthatareboundtogetherbysharingpairsofelectronsusingtheatomicorbitalsoftheboundatoms.CopyrightCengageLearning.Allrightsreserved43Section8.9The Localized Electron Bonding ModelLocalizedElectronModelElectronpairsareassumedtobelocalized不离
31、域的onaparticularatomorinthespacebetweentwoatoms:Lone pairs pairsofelectronslocalizedonanatomBonding pairs pairsofelectronsfoundinthespacebetweentheatomsdelocalized离域的CopyrightCengageLearning.Allrightsreserved44Section8.9The Localized Electron Bonding ModelLocalizedElectronModel1.Descriptionofvalencee
32、lectronarrangement(Lewisstructure).2.Predictionofgeometry(VSEPRmodel).3.Descriptionofatomicorbitaltypesusedbyatomstoshareelectronsorholdlonepairs.CopyrightCengageLearning.Allrightsreserved45Section8.10Lewis StructuresLewisStructureShowshowvalenceelectronsarearrangedamongatomsinamolecule.Reflectscent
33、ralideathatstabilityofacompoundrelatestonoblegaselectronconfiguration.CopyrightCengageLearning.Allrightsreserved46Section8.10Lewis StructuresHydrogenformsstablemoleculeswhereitsharestwoelectrons.DuetRuleSection8.10Lewis StructuresOctetRuleElementsformstablemoleculeswhensurroundedbyeightelectrons.Cop
34、yrightCengageLearning.AllrightsreservedSection8.10Lewis StructuresSingleCovalentBondAcovalentbondinwhichtwoatomsshareonepairofelectrons.HHCopyrightCengageLearning.Allrightsreserved49Section8.10Lewis StructuresDoubleCovalentBondAcovalentbondinwhichtwoatomssharetwopairsofelectrons.O=C=OCopyrightCengag
35、eLearning.Allrightsreserved50Section8.10Lewis StructuresTripleCovalentBondAcovalentbondinwhichtwoatomssharethreepairsofelectrons.CopyrightCengageLearning.Allrightsreserved51Section8.10Lewis StructuresStepsforWritingLewisStructures1.Sumthevalenceelectronsfromalltheatoms.2.Useapairofelectronstoformabo
36、ndbetweeneachpairofboundatoms.3.Atomsusuallyhavenoblegasconfigurations.Arrangetheremainingelectronstosatisfytheoctetrule(orduetruleforhydrogen).CopyrightCengageLearning.Allrightsreserved52Section8.10Lewis StructuresStepsforWritingLewisStructures1.Sumthevalenceelectronsfromalltheatoms.(Usetheperiodic
37、table.)Example:H2O2(1e)+6e=8etotalCopyrightCengageLearning.Allrightsreserved53Section8.10Lewis StructuresStepsforWritingLewisStructures2.Useapairofelectronstoformabondbetweeneachpairofboundatoms.Example:H2OCopyrightCengageLearning.Allrightsreserved54Section8.10Lewis StructuresStepsforWritingLewisStr
38、uctures3.Atomsusuallyhavenoblegasconfigurations.Arrangetheremainingelectronstosatisfytheoctetrule(orduetruleforhydrogen).Examples:H2O,PBr3,andHCNCopyrightCengageLearning.Allrightsreserved55Section8.10Lewis StructuresDrawaLewisstructureforeachofthefollowingmolecules:H2F2HFCopyrightCengageLearning.All
39、rightsreserved56CONCEPT CHECK!CONCEPT CHECK!Section8.10Lewis StructuresDrawaLewisstructureforeachofthefollowingmolecules:NH3CO2CCl4CopyrightCengageLearning.Allrightsreserved57CONCEPT CHECK!CONCEPT CHECK!Section8.11Exceptions to the Octet RuleBorontendstoformcompoundsinwhichtheboronatomhasfewerthanei
40、ghtelectronsaroundit(itdoesnothaveacompleteoctet).BH3=6eCopyrightCengageLearning.Allrightsreserved58Section8.11Exceptions to the Octet RuleWhenitisnecessarytoexceedtheoctetruleforoneofseveralthird-row(orhigher)elements,placetheextraelectronsonthecentralatom.SF4=34eAsBr5=40eCopyrightCengageLearning.A
41、llrightsreserved59Section8.11Exceptions to the Octet RuleDrawaLewisstructureforeachofthefollowingmolecules:BF3PCl5SF6CopyrightCengageLearning.Allrightsreserved60CONCEPT CHECK!CONCEPT CHECK!Section8.11Exceptions to the Octet RuleLetsReviewC,N,O,andFshouldalwaysbeassumedtoobeytheoctetrule.BandBeoftenh
42、avefewerthan8electronsaroundthemintheircompounds.Second-rowelementsneverexceedtheoctetrule.Third-rowandheavierelementsoftensatisfytheoctetrulebutcanexceedtheoctetrulebyusingtheiremptyvalencedorbitals.CopyrightCengageLearning.Allrightsreserved61Section8.11Exceptions to the Octet RuleLetsReviewWhenwri
43、tingtheLewisstructureforamolecule,satisfytheoctetrulefortheatomsfirst.Ifelectronsremainaftertheoctetrulehasbeensatisfied,thenplacethemontheelementshavingavailabledorbitals(elementsinPeriod3orbeyond).CopyrightCengageLearning.Allrightsreserved62Section8.12ResonanceMorethanonevalidLewisstructurecanbewr
44、ittenforaparticularmolecule.NO3=24eCopyrightCengageLearning.Allrightsreserved63Section8.12ResonanceActualstructureisanaverageoftheresonancestructures.Electronsarereallydelocalizedtheycanmovearoundtheentiremolecule.CopyrightCengageLearning.Allrightsreserved64Section8.12ResonanceDrawaLewisstructurefor
45、eachofthefollowingmolecules:COCO2CH3OHOCNCopyrightCengageLearning.Allrightsreserved65CONCEPT CHECK!CONCEPT CHECK!Section8.12ResonanceFormalChargeUsedtoevaluatenonequivalentLewisstructures.Atomsinmoleculestrytoachieveformalchargesasclosetozeroaspossible.形式电荷尽量接近零Anynegativeformalchargesareexpectedtor
46、esideonthemostelectronegativeatoms.CopyrightCengageLearning.Allrightsreserved66Section8.12ResonanceFormalChargeFormalcharge=(#valenceeonfreeneutralatom)(#valenceeassignedtotheatominthemolecule).Assume:Lonepairelectronsbelongentirelytotheatominquestion.Sharedelectronsaredividedequallybetweenthetwosha
47、ringatoms.CopyrightCengageLearning.Allrightsreserved67Section8.12ResonanceRulesGoverningFormalChargeTocalculatetheformalchargeonanatom:1.Takethesumofthelonepairelectronsandone-halfthesharedelectrons.2.Subtractthenumberofassignedelectronsfromthenumberofvalenceelectronsonthefree,neutralatom.CopyrightC
48、engageLearning.Allrightsreserved68Section8.12ResonanceConsidertheLewisstructureforPOCl3.Assigntheformalchargeforeachatominthemolecule.P:54=+1O:67=1Cl:77=0CopyrightCengageLearning.Allrightsreserved69CONCEPT CHECK!CONCEPT CHECK!Section8.12ResonanceRulesGoverningFormalChargeThesumoftheformalchargesofal
49、latomsinagivenmoleculeorionmustequaltheoverallchargeonthatspecies.CopyrightCengageLearning.Allrightsreserved70Section8.12ResonanceRulesGoverningFormalChargeIfnonequivalentLewisstructuresexistforaspecies,thosewithformalchargesclosesttozeroandwithanynegativeformalchargesonthemostelectronegativeatomsar
50、econsideredtobestdescribethebondinginthemoleculeorion.CopyrightCengageLearning.Allrightsreserved71Section8.13Molecular Structure: The VSEPR ModelVSEPRModelVSEPR:ValenceShellElectron-PairRepulsion.Thestructurearoundagivenatomisdeterminedprincipallybyminimizingelectronpairrepulsions.CopyrightCengageLe
51、arning.Allrightsreserved72Section8.13Molecular Structure: The VSEPR ModelStepstoApplytheVSEPRModel1.DrawtheLewisstructureforthemolecule.2.Counttheelectronpairsandarrangetheminthewaythatminimizesrepulsion(putthepairsasfarapartaspossible.3.Determinethepositionsoftheatomsfromthewayelectronpairsareshare
52、d(howelectronsaresharedbetweenthecentralatomandsurroundingatoms).4.Determinethenameofthemolecularstructurefrompositionsoftheatoms.CopyrightCengageLearning.Allrightsreserved73Section8.13Molecular Structure: The VSEPR ModelVSEPRCopyrightCengageLearning.Allrightsreserved74Section8.13Molecular Structure
53、: The VSEPR ModelVSEPR:TwoElectronPairsCopyrightCengageLearning.Allrightsreserved75Section8.13Molecular Structure: The VSEPR ModelVSEPR:ThreeElectronPairsCopyrightCengageLearning.Allrightsreserved76Section8.13Molecular Structure: The VSEPR ModelVSEPR:FourElectronPairsCopyrightCengageLearning.Allrigh
54、tsreserved77Section8.13Molecular Structure: The VSEPR ModelVSEPR:IodinePentafluorideCopyrightCengageLearning.Allrightsreserved78Section8.13Molecular Structure: The VSEPR ModelDeterminetheshapeforeachofthefollowingmolecules,andincludebondangles:HCNPH3SF4HCNlinear,180oPH3trigonalpyramid,109.5o(107o)SF
55、4seesaw,90o,120oCopyrightCengageLearning.Allrightsreserved79CONCEPT CHECK!CONCEPT CHECK!Section8.13Molecular Structure: The VSEPR ModelDeterminetheshapeforeachofthefollowingmolecules,andincludebondangles:O3KrF4O3bent,120oKrF4squareplanar,90o,180oCopyrightCengageLearning.Allrightsreserved80CONCEPT CH
56、ECK!CONCEPT CHECK!Section8.13Molecular Structure: The VSEPR ModelTrueorfalse:Amoleculethathaspolarbondswillalwaysbepolar.-Iftrue,explainwhy.-Iffalse,provideacounter-example.CopyrightCengageLearning.Allrightsreserved81CONCEPT CHECK!CONCEPT CHECK!Section8.13Molecular Structure: The VSEPR ModelLets Thi
57、nk About ItDrawtheLewisstructureforCO2.DoesCO2containpolarbonds?Isthemoleculepolarornonpolaroverall?Why?CopyrightCengageLearning.Allrightsreserved82Section8.13Molecular Structure: The VSEPR ModelTrueorfalse:Lonepairsmakeamoleculepolar.-Iftrue,explainwhy.-Iffalse,provideacounter-example.CopyrightCeng
58、ageLearning.Allrightsreserved83CONCEPT CHECK!CONCEPT CHECK!Section8.13Molecular Structure: The VSEPR ModelLets Think About ItDrawtheLewisstructureforXeF4.DoesXeF4containlonepairs?Isthemoleculepolarornonpolaroverall?Why?CopyrightCengageLearning.Allrightsreserved84Section8.13Molecular Structure: The V
59、SEPR ModelArrangementsofElectronPairsAroundanAtomYieldingMinimumRepulsionCopyrightCengageLearning.Allrightsreserved85Section8.13Molecular Structure: The VSEPR ModelStructuresofMoleculesThatHaveFourElectronPairsAroundtheCentralAtomSection8.13Molecular Structure: The VSEPR ModelStructuresofMoleculeswithFiveElectronPairsAroundtheCentralAtomCopyrightCengageLearning.Allrightsreserved87
