1Chapter9ChemicalBondingandMolecularStructure2Whatischemicalbonding?Chemicalbondsrefertothemain,direct,andstrongforcesbetweenatomsandions.Whatchemicalbondstypesarethere?covalentbondsionicbondsmetalbonds3Threeobjectives:CovalentbondingandatomiccrystalsIonicbondsandionicsubstancesIntermolecularforcesandmolecularcrystals49-1Covalentbonding

andatomiccrystals

9-1-1Valencebondingtheory9-1-2Hybridization9-1-3Valenceshellelectronpairrepulsion（VSEPR）9-1-4MolecularOrbitTheory5Question1:

Howdomoleculesformfromatomsofelementswiththesameorcloseelectronegativity?

WhythehydrogenmoleculeexistsasH2insteadofH3oranyothermolecularformula?

69-1-1ValencebondingtheoryFigure9-1RelationshipbetweenH2energyanditsnucleusdistance.

1916年,路易斯提出經典共價鍵理論;1927年,海特勒-倫敦等用量子力學處理氫分子結構.7Figure9-2SchematicsofHClbonding.Thebondingatomicorbitalsmustoverlapasmuchaspossible,thatis,theymustoverlapinthemaximumwavefunctiondirection.8價鍵理論(VB法)具有自旋方向相反的單電子的原子相互接近時,單電子可以配對構成共價鍵.重疊越多，形成的共價鍵越穩定，即原子軌道最大重疊原理.9共價鍵的特征1.具有飽和性（所形成的共價鍵數目取決于它所具有的未成對電子數）2.具有方向性（形成共價鍵時，原子間總是盡可能沿著原子軌道最大重疊的方向成鍵）10twotypesofcovalentbonds鍵型—

sigma(σ)bondsandpi(

)bonds

σ鍵，π鍵

Thelinethroughthetwonucleusiscalledinternuclearaxis(bondaxes鍵軸)x.sigmasymmetricalorbital,suchas

s,

px,

dx2-y2,

dz2;pisymmetricalorbital,suchas

py,

pz,

dxy,

dyz,

dxz.11p-p12Figure9-3Schematicofσbondsand

bonds.13Table9-1Comparisonsofσbondand

bondBondingSigmaBondsPiBondsWaystooverlapAlongthebondaxesAlongthedirectionperpendiculartothebondaxes

OverlapextentlargesmallBondenergylargesmallReactivityRelativelydifficultytotakepartinreactions

Easytoreact14Figure9-4Schematicofbondsinnitrogenmolecule.Singlebond:σbond

Doublebond:σbond+

bondTriplebond:σbond+2

bond15Figure9-5SchematicofH2Smoleculeforming.共價鍵的本質：核對負電區域的吸引。16正常共價鍵：共價鍵的共用電子對由成鍵原子雙方各提供一個電子而組成配位共價鍵coordinatedcovalentbond

：共用電子對由一方單獨提供。“”表示配位鍵，箭頭由給予體指向接受體.Coordinationcompounds/Complexes形成條件：成鍵原子一方有孤對電子，另一方有空軌道。17Iftheelectron-pairisprovidedbyoneatomandtheotheratomonlyprovidesanemptyorbital,theconsequentcovalentbondiscalledcoordinatedcovalentbond.Compoundswithcoordinatedcovalentbondarecalledcoordinationcompounds,orcomplexes.181MinutePaper：

WritedownthemoleculesthatcanbeexplainedbyapplyingValenceBondTheory?19Figure9-6Structuresofgraphite,diamondandfullereneC60.20Question2:

Howtoexplainthestructuresofgraphite,diamondandfullereneC60?

Howtodeterminethegeometricstructuresofmoleculesconsistingofonecentralatomsurroundedbyotheratoms,ABm,suchasCH4?

219-1-2Hybridization雜化

9-1-2-1HybridizationandHybridOrbitals

Figure9-7Anenergy-leveldiagramshowingtheformationoffoursp3orbitals.

雜化軌道：將不同類型的原子軌道重新組合成能量、形狀、方向與原來不同的新的軌道。22239-1-2-2MainPointsofHybridization（1）Therearemanytypesofhybridization;thenumberofhybridorbitalsequalsthenumberofatomicorbitalsinvolvedinhybridization.

只有能量相近（nsnp,nsnpnd,(n-1)d

nsnp）的價電子軌道才能相互雜化;雜化前后軌道數目不變.Forelementsinthesecondperiod,suchasBe,B,C,N,OandF,thevalenceorbitalsareone2sorbitalandthree2porbitals.s+p

2sphybridorbitalss+2p3sp2

hybridorbitalss+3p4sp3

hybridorbitals24Forelementsinthethirdperiod,suchasSi,P,S,Cl,thevalenceorbitalsareone3sorbital,three3porbitalsandfive3dorbitals.s+3p+d

5sp3dhybridorbitalss+3p+2d6sp3d2

hybridorbitals25Forelementsinthefourthperiod,thevalenceorbitalsare3dorbitals,one4sorbital,three4porbitalsandthe4dorbitals.Thus,besidestheabovefivetypesofhybridization,theatomicorbitalsmayformdsp2andd2sp3hybridorbitalsaswell.d+s+2p

4dsp2

hybridorbitals2d+s+3p6d2sp3

hybridorbitals26(2)Differenthybridorbitalshavedifferentshapes

雜化后軌道伸展方向，形狀和能量發生改變;雜化軌道的成鍵能力大于未雜化軌道,因為雜化軌道形狀變為一頭大一頭小.sp2sp3

Figure9-8Shapesofhybridorbitals.27dsp2sp3dsp3d2Figure9-8Shapesofhybridorbitals(continued).28sp3d雜化-PCl529sp3d2雜化-SF630(3)Thehybridorbitalsofthecentralatomwilloverlapwiththevalenceorbitalofanotheratomtoformasigmabond.Thestructureofthemoleculeisrelatedwiththeshapeofthehybridorbitals.nolonepair,equivalenthybridization(等性雜化)

lonepair,nonequivalenthybridization(不等性雜化)31Figure9-9Moleculestructuresofmethane,ammoniaandwater.tetrahedron

trigonalpyramidV-shaped,orbend

329-1-2-3ExampleAnalysis(1)BeCl2(g)Be2s2

Be*(here“*”representexcitedstate)2s12p1

equivalentsphybridization,twosporbitals(linear).

Eachsporbital,containingoneelectron,willoverlapwiththepxorbitalofaClatom,alsocontainingoneelectron,toformasigmabond.Therefore,TheCl-Be-Clmoleculehasalinearstructurewitha180-degreebondangle.33(2)BF3B2s22p1

B*2s12px12py1

equivalentsp2hybridization,threesp2orbitals(trigonalplanar).Eachsp2orbital,containingoneelectron,willoverlapwiththepxorbitalofaFatom,alsocontainingoneelectron,toformasigmabond.BF3

trigonalplanarstructurewith120-degreebondangles.34(3)CH2=CH2C2s22px12py12pz0

C*2s12px12py12pz1.Eachcarbonatomundergoesanequivalentsp2hybridization(using2s12px12py1)togetthreesp2orbitals(trigonalplanar).Eachcarbonatom,besidesformingthreesigmabondswiththeothercarbonatomandtwohydrogenatoms,usesthepzorbitaltoforma

pibondwiththeothercarbon.35(4)PCl5

P3s23p3

P*3s13px13py13pz13dz21.Thephosphorusatomundergoesequivalentsp3dhybridization.Eachsp3dorbital,containingoneelectron,willoverlapwiththepxorbitalofaClatom,alsocontainingoneelectron,toformasigmabond.

trigonalbipyramidal.36Table9-2RelationshipsoftheVariousTypesofHybridizationandTheirSpatialArrangement

TypesofhybridizationThenumberofhybridorbitals

Theangelsbetweenhybridorbitals

Shapesofhybridorbitals

Examples

sp2180°linearBeCl2

sp23120°trigonalplanarBF3sp34109.5°tetrahedronCH4

dsp2490°180°planarsquare

Ni(H2O)42+sp3d590°120°180°trigonalbipyramidal

PCl5

sp3d2/d2sp3

690°180°octahedralSF6，Fe(CN)63-

37HowtodeterminethegeometricstructuresofABmmoleculesorionsbyaeasymethod?389-1-3Valenceshellelectronpairrepulsion(VSEPR)In1940,VSEPRwasfirstaddressedbyaBritishchemistN.V.Sidgwick,andlaterwassupplementedbyR.J.Gillespie.399-1-3-1MainPointsThestructureofABmmoleculedependsonthevalenceelectronpairs.Inordertogetastablemoleculestructure,thevalenceelectronpairsshoulddepartasfarapartaspossible.

409-1-3-2GeneralRules(1)Determinethesumofvalenceelectrons.PO43-ionSO42-ionNH4+ion(5+3=8valenceelectrons)

(6+2=8valenceelectrons)(5+4-1=8valenceelectrons)(5+3=8valenceelectrons)PCl341(2)Counttheelectronpairsandarrangetheminthewaythatminimizesrepulsion,thatis,putthepairsasfarapartaspossible4243444546(3)Multiplebondscountasoneeffectiveelectronpair.Doublebondprovideszerochargeandtriplebondprovidesonenegativecharge.Therepulsionincreasesintheorder:triplebond>doublebond>singlebond47

Question3:

如何解釋H2+、O2+（單電子鍵）的存在?

如何解釋O2的順磁性？

說明：

分子中有成單電子，則為順磁性；

分子中無成單電子，則為抗磁性。

48物質的磁性：指宏觀物質的原子中的電子產生的磁性。

——

強磁性，分為鐵磁性和亞鐵磁性。

——

弱磁性，分為抗磁性、順磁性和反鐵磁性。

抗磁性（diamagnetism）物質的原子中電子磁矩互相抵消，合磁矩為零。順磁性（paramagnetism）物質的磁化率X=磁化強度（物質在外加磁場作用下的合磁矩,稱為磁化強度)與磁場強度之比,為正值，比反磁性大1～3個數量級，X約10-5～10-3。反鐵磁性（antiferromagnetism）:指在無外加磁場的情況下，磁疇內近鄰原子或離子的數值相等的磁矩，由于其間的相互作用而處于反平行排列的狀態，因而其合磁矩為零的現象。核磁性：指原子中的原子核具有的磁性。核磁共振成像(磁共振CT)499-1-4分子軌道理論（MolecularOrbitTheory）弄清分子軌道的數目和能級;原子算出可用來填充這些軌道的電子數;按一定規則將電子填入分子軌道,像寫原子的電子組態那樣寫出分子的電子組態。思路:ψ原子

ψ分子

A2分子軌道的能級圖

分子軌道式

分子的結構、性質

501.

理論要點（1）

分子中的電子不屬于某個原子，而屬于整個分子，其運動狀態由ψ分子來描述，ψ分子叫分子軌道；

（2）

來自不同原子的電子的原子軌道線性組合成分子軌道的條件：

對稱性匹配：——以x軸為鍵軸

分子軌道：s-ss-pxpx-px

分子軌道:py-py,py-dxy,dxy-dxy

最大重疊

能量相近51SigmaOrbital:

Abondingmolecularorbitalwithcylindricalsymmetryaboutaninternuclearaxis.52(3)原子軌道ψaψb線性組合有兩種方式，得到成鍵分子軌道和反鍵分子軌道:ψ

=c1(ψa+ψb);符號相同的ψaψb疊加，原子軌道相加重疊，兩核間幾率密度增大

，Eψ減小。ψ*

=c2(ψa-ψb);符號相反的ψaψb疊加，原子軌道相減重疊，兩核間幾率密度減小，Eψ*增大。535455565758

(4)原子軌道線性組合類型多樣，組合前后軌道數目相等（分子軌道數目=原子軌道數目）；由ψ分子

分子軌道的圖象、Ei(5)按分子軌道能量的大小，得到分子軌道近似能級圖；分子中電子的排布同樣遵從原子中電子排布的三原則：能量最低原理；保里不相容原理；洪特規則。59

1.盡先占據能量最低的軌道,低能級軌道填滿后才進入能級較高的軌道;2.每條分子軌道最多只能填入2個自旋相反的電子;3.分布到等價分子軌道時總是盡可能分占軌道.電子填入分子軌道時服從以下規則：60Whenatomicorbitalsarecombinedtogivemolecularorbitals,thenumberofmolecularorbitalsformedequalsthenumberofatomicorbitalsused.Sothetwo1sorbitalsofHcombinetogivetheorbitalsoftheH2molecule.Amolecularorbital(likeanatomicorbital)cancontainnomorethantwoelectrons(PauliExclusionPrinciple),andarefilledstartingwiththelowestenergyorbitalfirst.Ingeneral,theenergydifferencebetweenabondingandanti-bondingorbitalpairbecomeslargerastheoverlapoftheatomicorbitalsincrease.61TheH2moleculehastwovalenceelectrons.

62TheH2+moleculehasonlyonevalenceelectron.

63TheHe2+moleculehasthreevalenceelectrons.

6465IntheLewisStructureTheory(ValenceBondTheory)wehadsingle,double,andtriplebonds,intheMolecularOrbitalTheorywesimilarlydefinethebondorder.

Bondorder=1/2(#ofelectronsinbondingorbitals-#ofelectronsinanti-bondingorbitals).

鍵級=（成鍵電子數–反鍵電子數）/2

鍵級越大，鍵越牢固。

66Let'scalculatethebondorderinourfourexamplesabove.

BondOrderH2+1/2H21He2+1/2He20Thebondordermustbepositivenon-zeroforabondtobestable.He2hasabondorderofzeroandthatiswhytheHe2moleculeisnotobserved.

672.第二周期A2的分子軌道能級圖說明：①第二周期A2，F,O的2s2p原子軌道能量相差較大，而N,C,B的2s2p能級相近，∴分子軌道能級順序不同.68

2p2p2s2s

2s*2s

1s*1sMO1s1sAOAO*2*2*2

2

2

21s1s

1s*1s2s2s

2s*2sAO2p2p

MOAO*2*2*2

2

2

2O、F、NeB、C、N69707116O2的分子軌道式:(σ1s)2(σ*1s)2(σ2s)2(σ*2s)2(σ2px)2(

2py)2(

2pz)2(*2py)1(*2pz)1，兩個三電子鍵15O2+的分子軌道式:(σ1s)2(σ*1s)2(σ2s)2(σ*2s)2(σ2px)2

(

2py)2(

2pz)2(*2py)1(

2pz)三電子鍵，

鍵17O2-的分子軌道式:(σ1s)2(σ*1s)2(σ2s)2(σ*2s)2(σ2px)2

(

2py)2(

2pz)2(*2py)2(*2pz)1，一個三電子鍵18O22-的分子軌道式:(σ1s)2(σ*1s)2(σ2s)2(σ*2s)2(σ2px)2

(

2py)2(

2pz)2(*2py)2(*2pz)2，穩定性：O2+>O2>O2->O22-727314N2的分子軌道式:(σ1s)2(σ*1s)2(σ2s)2(σ*2s)2

(

2py)2(

2pz)2(σ2px)2

(*2py)(*2pz)(σ*

2px)

74②分子軌道能量決定于原子軌道的能量第二周期同一類型A2的分子軌道能量隨Z↑而↓。753.

第二周期AB的分子軌道能級圖eg1.14CO的分子軌道式:(σ1s)2(σ*1s)2(σ2s)2(σ*2s)2(

2py)2(

2pz)2(σ2px)2

等電子體：分子或離子，其原子數相同，所含電子數相同，稱為等電子體。等電子體性質相似。例如：22CO2N2ON3-NO2+(π34)32

BO33-,CO32-,NO3-50SiO44-,PO43-,SO42-,ClO4-76eg2.HF1H1s19F1s22s22p5H-F

σ對稱性：1s2s2px能量相近:1s(H)-13.6eV1s(F)–696.3eV2s(F)–40.1eV2p(F)-18.6eV

77Figure9-12Apartialmolecularorbitalenergy-leveldiagramfortheHFmolecule非鍵軌道：在形成分子后仍保持原來原子軌道的性質，稱為非鍵軌道。784.鍵參數與分子性質鍵能，鍵長，鍵角，鍵級，鍵的極性——鍵距。鍵能：0K,1.01325

105Pa,ABA+B所需的能量。鍵能越大，分子越穩定。對于雙原子分子，鍵能=鍵的離解能對于多原子分子，鍵能=鍵的離解能的平均值比較：鍵焓：298K,1.01325105Pa,ABA+B所需的能量。鍵長：核間的距離。鍵長越小，鍵越牢固。鍵角：鍵與鍵之夾角。鍵級：越大，鍵越牢固。鍵的極性：兩原子不同，電負性不同，電子對偏向電負性大的原子。799-2IonicBondsandIonicSubstances

9-2-1IonicBondsnNa(3s1)-ne-→nNa+(2s22p6)nCl(3s23p5)+ne-→nCl-(3s23p6)nNa+(2s22p6)+nCl-(3s23p6)→nNaClTheattractionbetweenpositivelychargedionsandnegativelychargedionsinioniccompoundsiscalledionicbond.80Table9-4TherelationshipbetweenElectronegativeDifferenceintheBondingAtomsandPercentofIonicCharacterofaBond

ElectronegativeDifferenceΔX

PercentofIonicCharacterofaBond/%ElectronegativeDifferenceΔX

PercentofIonicCharacterofaBond/%0.211.8550.442.0630.692.2700.8152.4761.0222.6821.2302.8861.4393.0891.6473.292ΔX=1.5,50%;CsF的離子性為92%。819-2-2StructureTypesofIonicCrystalsFigure.Cesiumchlorideandsodiumchlorideandzincsulfideunitcells.82Table9-5RadiiRatiosandCoordinateNumbersandGeometryr+/r-

CoordinateNumbersStructuresLatticesExamples225~0.4144TetrahedralFace-centeredcubicunit

ZnS0.414~0.7326OctahedralFace-centeredcubicunit

NaCl0.732~18CubicBody-centeredcubicunitCsCl839-2-3LatticeEnergyThelatticeenergyreferstothereleasedenergywhenforming1molioniccrystalsfromgaseouscationsandanionsattheabsolutezerodegree,1.01325

105Pa,denotedasU0(kJ·mol-1).Thelatticeenthalpyreferstothereleasedenergywhenforming1molioniccrystalsfromgaseouscationsandanionsatthe298K,1.01325

105Pa.

84Example9-1CalculatethelatticeenergyforNaFusingthefollowingthermochemicaldata.ProcessesEnergyChanges/kJ·mol-1

Na(s)→Na(g)S=108.8Na(g)→Na+(g)+e-I1=502.31/2F2(g)→F(g)1/2D=1/2

153.2F(g)+e-→F-(g)E1=–349.5Na+(g)+F-(g)→NaF(s)U0

Na(s)+1/2F2(g)

NaF(s)

rH

m=-569.3SOLUTION

rH

m=S+I1+1/2D+E1+U0U0=

rH

m-(S+I1+1/2D+E1)=-569.3-(108.8+502.3+1/2

153.2-349.5)=-907.5(kJ·mol-1)

85Born–LandeequationU0=138940AZ+Z-(1–1/n)/R0

AiscalledMadelungconstant

nisBornconstantR0isthedistancebetweenthetwonucleusZ+andZ-arechargenumber86Theionicbonddependsonionchargesionradiiionconfi