《无机化学简明教程》课件-Chapter 9 Chemical Bonds and M

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,路易斯提出经典共价键理论;1927年,海特勒-伦敦等用量子力学处理氢分子结构.7Figure9-2SchematicsofHClbonding.Thebondingatomicorbitalsmustoverlapasmuchaspossible,thatis,theymustoverlapinthemaximumwavefunctiondirection.8价键理论(VB法)具有自旋方向相反的单电子的原子相互接近时,单电子可以配对构成共价键.重叠越多，形成的共价键越稳定，即原子轨道最大重叠原理.9共价键的特征1.具有饱和性（所形成的共价键数目取决于它所具有的未成对电子数）2.具有方向性（形成共价键时，原子间总是尽可能沿着原子轨道最大重叠的方向成键）10twotypesofcovalentbonds键型—

sigma(σ)bondsandpi(

)bonds

σ键，π键

Thelinethroughthetwonucleusiscalledinternuclearaxis(bondaxes键轴)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.共价键的本质：核对负电区域的吸引。16正常共价键：共价键的共用电子对由成键原子双方各提供一个电子而组成配位共价键coordinatedcovalentbond

：共用电子对由一方单独提供。“”表示配位键，箭头由给予体指向接受体.Coordinationcompounds/Complexes形成条件：成键原子一方有孤对电子，另一方有空轨道。17Iftheelectron-pairisprovidedbyoneatomandtheotheratomonlyprovidesanemptyorbital,theconsequentcovalentbondiscalledcoordinatedcovalentbond.Compoundswithcoordinatedcovalentbondarecalledcoordinationcompounds,orcomplexes.181MinutePaper：

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

Howtoexplainthestructuresofgraphite,diamondandfullereneC60?

Howtodeterminethegeometricstructuresofmoleculesconsistingofonecentralatomsurroundedbyotheratoms,ABm,suchasCH4?

219-1-2Hybridization杂化

9-1-2-1HybridizationandHybridOrbitals

Figure9-7Anenergy-leveldiagramshowingtheformationoffoursp3orbitals.

杂化轨道：将不同类型的原子轨道重新组合成能量、形状、方向与原来不同的新的轨道。22239-1-2-2MainPointsofHybridization（1）Therearemanytypesofhybridization;thenumberofhybridorbitalsequalsthenumberofatomicorbitalsinvolvedinhybridization.

只有能量相近（nsnp,nsnpnd,(n-1)d

nsnp）的价电子轨道才能相互杂化;杂化前后轨道数目不变.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

杂化后轨道伸展方向，形状和能量发生改变;杂化轨道的成键能力大于未杂化轨道,因为杂化轨道形状变为一头大一头小.sp2sp3

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

lonepair,nonequivalenthybridization(不等性杂化)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:

如何解释H2+、O2+（单电子键）的存在?

如何解释O2的顺磁性？

说明：

分子中有成单电子，则为顺磁性；

分子中无成单电子，则为抗磁性。

48物质的磁性：指宏观物质的原子中的电子产生的磁性。

——

强磁性，分为铁磁性和亚铁磁性。

——

弱磁性，分为抗磁性、顺磁性和反铁磁性。

抗磁性（diamagnetism）物质的原子中电子磁矩互相抵消，合磁矩为零。顺磁性（paramagnetism）物质的磁化率X=磁化强度（物质在外加磁场作用下的合磁矩,称为磁化强度)与磁场强度之比,为正值，比反磁性大1～3个数量级，X约10-5～10-3。反铁磁性（antiferromagnetism）:指在无外加磁场的情况下，磁畴内近邻原子或离子的数值相等的磁矩，由于其间的相互作用而处于反平行排列的状态，因而其合磁矩为零的现象。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分子轨道理论（MolecularOrbitTheory）弄清分子轨道的数目和能级;原子算出可用来填充这些轨道的电子数;按一定规则将电子填入分子轨道,像写原子的电子组态那样写出分子的电子组态。思路:ψ原子

ψ分子

A2分子轨道的能级图

分子轨道式

分子的结构、性质

501.

理论要点（1）

分子中的电子不属于某个原子，而属于整个分子，其运动状态由ψ分子来描述，ψ分子叫分子轨道；

（2）

来自不同原子的电子的原子轨道线性组合成分子轨道的条件：

对称性匹配：——以x轴为键轴

分子轨道：s-ss-pxpx-px

分子轨道:py-py,py-dxy,dxy-dxy

最大重叠

能量相近51SigmaOrbital:

Abondingmolecularorbitalwithcylindricalsymmetryaboutaninternuclearaxis.52(3)原子轨道ψaψb线性组合有两种方式，得到成键分子轨道和反键分子轨道:ψ

=c1(ψa+ψb);符号相同的ψaψb叠加，原子轨道相加重叠，两核间几率密度增大

，Eψ减小。ψ*

=c2(ψa-ψb);符号相反的ψaψb叠加，原子轨道相减重叠，两核间几率密度减小，Eψ*增大。535455565758

(4)原子轨道线性组合类型多样，组合前后轨道数目相等（分子轨道数目=原子轨道数目）；由ψ分子

分子轨道的图象、Ei(5)按分子轨道能量的大小，得到分子轨道近似能级图；分子中电子的排布同样遵从原子中电子排布的三原则：能量最低原理；保里不相容原理；洪特规则。59

1.尽先占据能量最低的轨道,低能级轨道填满后才进入能级较高的轨道;2.每条分子轨道最多只能填入2个自旋相反的电子;3.分布到等价分子轨道时总是尽可能分占轨道.电子填入分子轨道时服从以下规则：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).

键级=（成键电子数–反键电子数）/2

键级越大，键越牢固。

66Let'scalculatethebondorderinourfourexamplesabove.

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

672.第二周期A2的分子轨道能级图说明：①第二周期A2，F,O的2s2p原子轨道能量相差较大，而N,C,B的2s2p能级相近，∴分子轨道能级顺序不同.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的分子轨道式:(σ1s)2(σ*1s)2(σ2s)2(σ*2s)2(σ2px)2(

2py)2(

2pz)2(*2py)1(*2pz)1，两个三电子键15O2+的分子轨道式:(σ1s)2(σ*1s)2(σ2s)2(σ*2s)2(σ2px)2

(

2py)2(

2pz)2(*2py)1(

2pz)三电子键，

键17O2-的分子轨道式:(σ1s)2(σ*1s)2(σ2s)2(σ*2s)2(σ2px)2

(

2py)2(

2pz)2(*2py)2(*2pz)1，一个三电子键18O22-的分子轨道式:(σ1s)2(σ*1s)2(σ2s)2(σ*2s)2(σ2px)2

(

2py)2(

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

(

2py)2(

2pz)2(σ2px)2

(*2py)(*2pz)(σ*

2px)

74②分子轨道能量决定于原子轨道的能量第二周期同一类型A2的分子轨道能量随Z↑而↓。753.

第二周期AB的分子轨道能级图eg1.14CO的分子轨道式:(σ1s)2(σ*1s)2(σ2s)2(σ*2s)2(

2py)2(

2pz)2(σ2px)2

等电子体：分子或离子，其原子数相同，所含电子数相同，称为等电子体。等电子体性质相似。例如：22CO2N2ON3-NO2+(π34)32

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

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

77Figure9-12Apartialmolecularorbitalenergy-leveldiagramfortheHFmolecule非键轨道：在形成分子后仍保持原来原子轨道的性质，称为非键轨道。784.键参数与分子性质键能，键长，键角，键级，键的极性——键距。键能：0K,1.01325

105Pa,ABA+B所需的能量。键能越大，分子越稳定。对于双原子分子，键能=键的离解能对于多原子分子，键能=键的离解能的平均值比较：键焓：298K,1.01325105Pa,ABA+B所需的能量。键长：核间的距离。键长越小，键越牢固。键角：键与键之夹角。键级：越大，键越牢固。键的极性：两原子不同，电负性不同，电子对偏向电负性大的原子。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的离子性为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