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1、1 Chapter6MoleculesandCovalentCompounds 6 3MultipleCovalentBondsandResonance Copyright 2005byPearsonEducation Inc PublishingasBenjaminCummings 2 MultipleBonds Inasinglebond Onepairofelectronsisshared Inadoublebond Twopairsofelectronsareshared Inatriplebond Threepairsofelectronsareshared 3 Electron D
2、otFormulaof CS2 Writetheelectron dotformulaforCS2 STEP1Determinetheatomarrangement TheCatomisthecentralatom SCSSTEP2Addthevalenceelectronsfor1Cand2S 1C 4e 2S 6e 16e 4 Electron DotFormulaCS2 STEP3AttacheachSatomtoCwithoneelectronpair S C SCalculatetheremainingelectrons 16e 4e 12e left 5 Electron DotF
3、ormulaCS2 STEP4Attach12remainingelectronsas6lonepairstocompleteoctets S C S STEP5Tocompleteoctets movetwolonepairsbetweenCandSatomstogivetwodoublebonds S C S or S C S 6 MultipleBondsinN2 InnitrogenN2 Octetsareachievedbysharingthreepairsofelectrons whichisatriplebond 7 SomeElectron DotFormulas 8 Reso
4、nancestructuresare Twoormoreelectron dotformulasforthesamearrangementofatomsRelatedbyadouble headedarrowWrittenbychanginglocationofadoublebondfromthecentralatomtoadifferentattachedatomSometimeswrittenasahybridresonancestructure ResonanceStructures 9 ResonancestructuresforNO3 are O O O NNN O O O O O
5、O ResonanceStructures 10 Carbonatehasthreeresonancestructures Ifthefollowingisone whataretheothertwo 2 O C O O LearningCheck 11 Carbonatehasthreeresonancestructures Ifthefollowingisone whataretheothertwo 2 2 2 O O O CCC O O O O O O Solution 12 CyanateionNCO hasthreeresonancestructures STEP1Writethea
6、rrangementofatoms NCO STEP2Countthevalenceelectrons 1N 5e 1C 4e 1O 6e charge 1e 16e STEP3Connectbondedatomsbysingleelectronpairs N C O 4e usedDeterminetheremainingelectrons 16e 4e 12e WritingResonanceStructures 13 STEP4Add12remainingelectronsas6lonepairs N C O STEP5Formdoubleortriplebondstomakeoctets N C O N C O N C O WritingResonanceStructures 14 WritetworesonancestructuresfornitriteNO2 LearningCheck 15 NO2 18e Electron dotformula O N O Usingadoublebondtocompleteoctetsgivestworesonancestructures O N O O N O Solution
