《無機(jī)化學(xué)簡明教程》課件-Chapter 8 Atomic Structure

1Chapter8AtomicStructure

Threeobjectives:Todescribethemovementstatesofelectrons

TointroducetheelectronconfigurationsTorevealtherelationshipbetweentheelectronicstructureandperiodicity21MovementsofElectronsinAtoms

Solutions:Experiments

ConclusionsApplyingthequantumnumbersobtainingfromtheSchr?dingerequationtodescribe.Movementsofsubmicroscopicparticles(r<10-8m)aredifferentfrommacroscopicalobjects.3玻爾In1922OttoStern斯特恩(1888–1969)In1943E.Schr?dinger薛定諤(1887-1961）In1933Ernest

Rutherford盧瑟福（1871-1937)in1908FatheroftheAtomicandNuclearPhysics‘a(chǎn)llscienceiseitherphysicsorstampt-collecting’JosephJohnThomson湯姆孫（1856～1940)Cavendish卡文迪什實(shí)驗(yàn)室

451-1CharacteristicsofElectronMovements

1-1-1TheEnergyofElectronsinAtomsIsQuantized量子性Figure8-1Experimentaldevicegeneratingthehydrogenspectrumandthehydrogenlinespectrumcontainsonlyafewdiscretewavelengthsinvisiblelightrange(1885,SwissphysicistBalmer).6In1913,SwedenphysicistRydberg

v=c/

=R(1/n12-1/n22)=3.289

1015(1/n12-1/n22)RydbergconstantR=

3.289

1015s-1;

n1,n2arepositiveintegrals,andn2>n1.7Anunsatisfactoryatomicmodel根據(jù)經(jīng)典物理學(xué)概念：

電子在運(yùn)動過程中要發(fā)射電磁波，氫原子光譜應(yīng)為連續(xù)光譜；帶電微粒在力場中運(yùn)動時總要產(chǎn)生電磁輻射并逐漸失去能量,運(yùn)動著的電子軌道會越來越小,最終將與原子核相撞并導(dǎo)致原子毀滅.由于原子毀滅的事實(shí)從未發(fā)生而且原子光譜是線狀,且有規(guī)律性。這些都是經(jīng)典物理學(xué)概念無法解釋的。8量子論：物質(zhì)吸收和發(fā)射能量是不連續(xù)的，即物質(zhì)只能以一最小單位(hν)一份一份的方式吸收或發(fā)射能量，能量最小的單位是光量子。玻爾理論建立在普朗克的量子論和愛因斯坦的光子學(xué)說的基礎(chǔ)上：愛因斯坦的光子學(xué)說認(rèn)為光既是一種波，又有粒子性。

E=hν

Ｅ－光量子的能量ν－光的頻率

p－光量子的動量λ－光的波長

h—普蘭克常數(shù)9TheBohrmodelincludestwopoints:

(1)Electroninahydrogenmovesaroundthenucleusonlyincertainallowedcircularorbitswhichmustmeetthefollowingrequirement,eachorbitwasassignedanumbercalledtheprincipalquantumnumbern(主量子數(shù)):

mrv=nh/2πn=1,2,3…mismassofanelectron;

risthedistancefromanelectrontothenucleus;

visspeedofelectron;

h=6.626

10-34J?s(Plankconstant).10(2)Whentheelectronisinthelowestenergyorbit,thehydrogenatomissaidtobeinitsgroundstate(基態(tài)).Asenergy(electromagnetic,thermal,orelectrical)isaddedtotheatom,theelectronisraisedtohigherandhigherenergylevels(能級)fartherandhigherfromthenucleus.Whentheelectronisinanyhigherenergylevel,thehydrogenatomissaidtobeinanexcitedstate(激發(fā)態(tài)).

v=(Efinal-Einitial)/h

11

r=0.529n2Ao

E=-2.178×10-18Z2/n2J

n=1，r

1=0.529Ao,E

1=-2.179×10-18Jn=2，r

2=22×0.529Ao,E

2=-2.179×10-18/4Jn=3，r

3=32×0.529Ao,E

3=-2.179×10-18/9J……n=∞

,r∞

=∞

(infinite：電離了),E=0J12r

1=0.529Ao

Bohrradius

ΔE=Einfinite-E1

=[0-(-2.179×10-18J)]×6.02×1023mol-1

=l3l2kJ?mol-1.

ionizationenergyofthehydrogenatom

13Figure8-2Theenergylevelsoftheorbitsforhydrogenatom.v=(Efinal-Einitial)/h

14ThephenomenacannotbeinterpretedbyBohr’stheory:eachspectrallineconsistsoftwocloselineseachspectrallinesplitintotwoormorelinesinmagneticfieldsthespectraofpolyelectronicatoms

151913年《論原子構(gòu)造和分子構(gòu)造》，首次打開了人類認(rèn)識原子結(jié)構(gòu)的大門，為近代物理研究開辟了道路。量子力學(xué)是以玻爾為領(lǐng)袖的一代杰出物理學(xué)家集體才華的結(jié)晶。161-1-2TheMovementofElectronsinAtomsIsStatistical

統(tǒng)計(jì)性（1）DeBroglie’sEquation德布羅意方程（1924）

dualnatureoflight

Einsteinmass-energyrelation

:E=mc2E=h

P=mc=E/c=h

/c=h/

=h/P=h/mv

deBroglieequationDeBroglie’swaveortheparticle’swave.17Figure8-3Davissson-Germer

Electrondiffractionstestin1927.18(2)TheHeisenbergUncertaintyPrinciple(in1927)

海森堡不準(zhǔn)確關(guān)系

?x·?P≥h/2π?x·?v≥h/2πm

?P:theuncertaintyinmomentum?x:theuncertaintyinpositionoftheparticle?v:theuncertaintyinitsspeedm:themassoftheparticleinkg

h=6.626×10-34J?s

19Usuallyelectronsmoveataspeedneartolightspeed,itssizeislargelysmallerthan10-10m.Thustolocateitprecisely,?xshouldbelessthan10-11m,thentheuncertaintyinthespeedoftheelectron

?v≥h/2πm·?x=6.626

10-34/2

3.14

9.11

10-31

10-11=1.16

107(m?s-1)20Table8-1

ComparisonsonMovementsofSubmicroscopicParticlesandMacroscopicalObjects

MacroscopicalObjectsNewtonmechanicallaw

F=ma

Thestateofobjects(speedandposition)atanyinstantcanbepreciselydetermined.SubmicroscopicParticles/r<10-8mQuantummechanicalmodel?2Ψ/?x2+?2Ψ/?y2+?2Ψ/?z2

=-8π2m(E–V)Ψ/h2Thestateofsubmicroscopicparticles(energyandpossibility)atanyinstantcanbeexpressedbyΨ(x,y,z).

?x·?v≥h/2πm

21在L.V.德布羅意的微觀粒子具有波粒二象性的基礎(chǔ)上，1926年薛定諤提出用波動方程描述微觀粒子運(yùn)動狀態(tài)的理論，后稱薛定諤方程，奠定了波動力學(xué)的基礎(chǔ).1944年，薛定諤著《生命是什么》一書，試圖用熱力學(xué)、量子力學(xué)和化學(xué)理論來解釋生命的本性。這本書使許多青年物理學(xué)家開始注意生命科學(xué)中提出的問題，引導(dǎo)人們用物理學(xué)、化學(xué)方法去研究生命的本性，使薛定諤成為蓬勃發(fā)展的分子生物學(xué)的先驅(qū)。E.Schr?dinger薛定諤（1887～1961）Austrianphysicist1933年，與狄拉克共同獲得諾貝爾物理學(xué)獎221-2Descriptionsofelectronmovements1-2-1波函數(shù)Ψ量子力學(xué)用波函數(shù)Ψ來描述原子中電子的運(yùn)動。23Ψ是如何得到的？——薛定諤方程波函數(shù)與薛定諤方程24★

方程中既包含體現(xiàn)微粒性的物理量m,也包含體現(xiàn)波動性的物理量ψ★

求解薛定鍔方程,就是求得波函數(shù)ψ和能量

E★

解得的ψ不是具體的數(shù)值,而是包括三個常數(shù)(n,l,m)和三個變量(r,θ,φ)的函數(shù)式Ψn,l,m(r,θ,φ)★

數(shù)學(xué)上可以解得許多個Ψn,l,m(r,θ,φ),但其物理意義并非都合理★有合理解的函數(shù)式叫做波函數(shù),它們以n,l,m的合理取值為前提。每個合理的解Ψ就是表示電子運(yùn)動的某一穩(wěn)定狀態(tài)。波函數(shù)=薛定鍔方程的合理解=原子軌道

25在量子力學(xué)中，用波函數(shù)和與其對應(yīng)的能量來描述電子的運(yùn)動狀態(tài)。Ψ是描述電子運(yùn)動狀態(tài)的數(shù)學(xué)表達(dá)式，Ψ的空間圖象叫原子軌道，原子軌道的數(shù)學(xué)表達(dá)式就是波函數(shù)。26波函數(shù)的物理意義電子云是電子出現(xiàn)概率密度的形象化描述。

：原子空間上某點(diǎn)附近單位微體積內(nèi)電子出現(xiàn)的概率，即概率密度（幾率密度）。小黑點(diǎn)較密的地方，概率密度較大，單位體積內(nèi)電子出現(xiàn)的機(jī)會多。如1s的電子云Ψ是描述核外電子運(yùn)動狀態(tài)的數(shù)學(xué)表達(dá)式，它描述了電子運(yùn)動的方式和規(guī)律271-2-2TheThreeQuantumNumbersprincipalquantumnumber,n:1,2,3,4,5,6,7,8,…,

withcorrespondingsymbols:K,L,M,N,O,P,Q,R…tellsthesizeofanorbitalandlargelydeterminesitsenergyhydrogenandHe+,Li2+,B3+theenergy

En=-2.179×10-18

Z2/n2(J)

28angularmomentumquantumnumber角量子數(shù),l:0,1,2,3,4,5,…n-1,spdfgh…tellstheshapeoftheorbitalsForpolyelectronicatoms,Ens

Enp

End

Enf,theenergiesofdifferentsubshellaredifferent,hereEnliscalledenergylevel.En,l=-2.179×10-18

Z*2/n2(J)29Figure8-4Boundarysurfacediagramsfors,p,dorbitals.30magneticquantumnumber磁量子數(shù)

ml:-lto+l

311-2-3PicturesofOrbitals

chargeclouds,boundarysurfacediagramandplotsofradialprobability.

Figure8-5(a)Chargecloudofthe1sorbitalofahydrogenatom.(b)Boundarysurfacediagramfor1sorbital.32Figure8-7Planarschematicforboundarysurfacesofs,p,dorbitals.33Figure8-6Radialprobabilityplottedagainstdistancefromthenucleusforahydrogenelectronindifferentorbitals.341-2-4

ElectronSpin

andPauliExclusionPrincipleIn1925,HollandgraduatesputforwardahypothesisofElectronSpin,AustrianphysicistPaulisuggestedthefourthquantum.Figure8-8SchematicofStern–Gerlachexperimentin1922.OttoStern斯特恩(1888–1969)In194335PauliexclusionprinciplePauliproposedthatinagivenatomnotwoelectronscanhavethesamesetoffourquantumnumbers(n,l,m,

and

ms).

36小結(jié)電子具有波粒二象性，需按幾率分布的統(tǒng)計(jì)規(guī)律來進(jìn)行研究。波函數(shù)是描述核外電子運(yùn)動狀態(tài)的數(shù)學(xué)表達(dá)式，其空間圖象為“原子軌道”。幾率密度|Ψ|2

是電子在原子核外空間某處單位體積內(nèi)出現(xiàn)的概率。用小黑點(diǎn)表示其分布所得的空間圖象。描述原子中電子狀態(tài)需用四個量子數(shù)：主量子數(shù)(n)、角量子數(shù)(l)、磁量子數(shù)(m)、自旋量子數(shù)(ms)。37nιm軌道/數(shù)電子數(shù)(2n2)K1s00１s122L2s0０2s428p10、

±12p6M3s003s9218p10、

±1３p6d20、±1、±23d10N4s004s16232p10、±14p6d20、±1、±24d10f30、±1、±2、±34f1438Exercises：描述原子中電子運(yùn)動狀態(tài)的四個量子數(shù)的物理意義各是什么？它們的可能取值是什么？下列各組量子數(shù)哪些是不合理的，為什么？

(1)n=2,l=1,m=0(2)n=2,l=2,m=-1(3)n=3,l=0,m=0(4)n=3,l=1,m=1(5)n=2,l=0,m=-1(6)n=2,l=3,m=2下列說法是否正確？不正確的應(yīng)該如何改正？s電子繞核運(yùn)動，其軌道為一圓周，而p電子是走8字形的；主量子數(shù)n為1時，有自旋相反的兩條軌道；主量子數(shù)n為4時，其軌道總數(shù)為16，電子層電子最大容量為32；主量子數(shù)n為4時，有3s,3p,3d三條軌道。39核外電子運(yùn)動的特征核外電子運(yùn)動的描述Reviewsn-1≥l

≥

∣m

∣,

ms=+1/2?x·?P≥h/2π?x·?v≥h/2πm

40zx++++++++++++++-------------zzzzzxxxxxxxyyyyspypxpzdxydyzdxzdz2

dx2-y2ReviewsHydrogenandHe+,Li2+,B3+:En=-2.179×10-18

Z2/n2(J)41Polyelectronicatoms:En,l=-2.179×10-18

Z*2/n2(J)422ElectronArrangements多電子原子的能級,原子軌道能級圖核外電子排布的規(guī)則，核外電子排布432-1OrbitalEnergyLevelsinPolyelectronicAtoms

2-1-1OrbitalEnergiesinPolyelectronicAtomsSlater斯萊特中心勢場模型：Theelectronisscreenedorshieldedfromthenuclearchargebytherepulsionsoftheotherelectrons.Thedecreaseofthenuclearchargebytheother(Z-1)e-iscalledscreeneffect

or

shieldeffect屏蔽效應(yīng).Thedecreasedpartiscalledthescreenconstantorshieldconstant屏蔽常數(shù)

σ.TheeffectivenuclearchargeZ*=Z-σ

44Z－σ=Z*，Z*——有效核電荷數(shù)σ為屏蔽常數(shù)，可用斯萊特經(jīng)驗(yàn)規(guī)則算得。屏蔽效應(yīng)：把多電子原子中其余電子對指定的某電子的作用近似地看作抵消一部分核電荷對該指定電子的吸引。En,l=-2.179×10-18

Z*2/n2(J)45(1s)(2s,2p)(3s,3p)(3d)(4s,4p)(4d)(4f)(5s,5p)…

(1)Theouterelectronsdon’tscreentheinnerelectrons,σ=0；(2)Whenthescreenedelectronisnsornpelectron,thescreenconstantforelectronsinthesamegroup:σ=0.35(forthetwoelectronsin1sorbital,σ=0.30);thescreenconstantforelectronsinthenext-to-the-outermostor(n-1)group:σ=0.85,thescreenconstantforelectronsinthenext-to-the-next-to-the-outermostor(n-2)shellandmoreinnershell:σ=1；(3)Whenthescreenedelectronisndornf,thescreenconstantamongthesamegroup:σ=0.35,thescreenconstantforelectronsintheleftside:σ=1.46Example8-1Calculatetheenergylevelsfor1sorbitaland2sorbitaloflithiumatom.

SOLUTIONLithiumatomhasthreeelectronswhichcanbedividedasbelow:(1s)2(2s)1

For1selectron,σ=0.3,Z*=3-0.3=2.7E1s=-2.179

10–18

2.72/12=-15.88

10–18(J)

For2selectron,σ=2

0.85=1.7,Z*=3-1.7=1.3E2s=-2.179

10–18

1.32/22=-0.92

10–18(J)

Therefore,E1s

<E2s47Example8-2Calculatetheenergylevelsfor3s、3p、3dand4sorbitalsofpotassiumatom.

SOLUTIONConsiderthepotassiumatom,whichhas19electrons:(1s)2(2s,2p)8(3s,3p)8(3d)1(4s,4p)For3selectron,σ=1×2+0.85×8+0.35×7=11.25，

Z*=19-11.25=7.75，

E3s=-2.179×10-18×7.752/32=-14.542×10-18(J)AccordingtoSlaterrule,E3s=E3p(Infact,E3s<E3passhowninFigure8-9,forSlaterruleisjustanapproximatecalculation.)For3delectron,σ=18，Z*=1,E3d=-2.179×10-18/32=-0.242×10-18(J)Supposethattheoutmostelectronisin4sorbital,thenfor4sorbital:σ=1×10+0.85×8=16.8，Z*=2.20,E4s

=-2.179×10-18

Z*2/n2=-2.179×10-18×2.202/42

=-0.66×10-18(J)Thatis,E3s=

E3p

<E4s<E3d.能級分裂;能級交錯.482-1-2Cotton’sOrbitalDiagram

Figure8-9PlotsoforbitalenergiessequencesuggestedbyCotton.49(1)Forhydrogenatom,Z=1,itsorbitalenergyisdeterminedbytheprinciplequantumnumber,n;

En=-2.179×10-18

Z2/n2J

,andEns=Enp

=End

=Enf.

(2)Forpolyelectronicatoms,theattractionofnucleuschargestotheelectronsincreasewiththeincreasingatomicnumber,theorbitalenergydecreaseswiththeincreasingatomicnumber.E1s(Cl)=-2.179×10-18(17-0.3)2/12J=-607.7×10-18(J)；

E1s(H)=-2.179×10-18JE1s(Cl)<E1s(H).50Figure8-9PlotsoforbitalenergiessequencesuggestedbyCotton.51(3)Forpolyelectronicatoms,theelectronsindifferentoutersubshellsarescreeneddifferently,whichcausesplitoforbitalenergies(能級分裂);thatis,Ens<Enp<E

nd<Enf.Thesephenomenacanbeexplainedbypenetrationeffect(鉆穿效應(yīng)).

(4)Forpolyelectronicatoms,thesequenceoforbitalsinenergyisdifferent.Forsomeatoms,orbitalenergiesinterlace(能級交錯).Forexample,Z=15~20,

E3d>E4s,whileZ<15andZ>20,E3d<E4s.Thisisduetothepenetrationeffectaswell.52鉆穿效應(yīng):外層電子向內(nèi)層鉆穿的效應(yīng)，進(jìn)入原子內(nèi)部空間，受到核的較強(qiáng)的吸引作用，能量會降低。3d與

4s軌道的徑向分布圖532-1-3Pauling’sOrbitalDiagramLinusCarlPauling鮑林（1901-1994）In195454Table8-3GroupsofOrbitalEnergyLevelsSuggestedbyPauling

GroupsofOrbitalEnergyLevels

OrbitalsinEachGroupⅠ1sⅡ2s2pⅢ3s3pⅣ4s3d4pⅤ5s4d5pⅥ6s4f5d6pⅦ7s5f6d7pⅧ8s5g6f7d8pⅨ9s6g7f8d9p552-2ThreeRulesforElectronArrangements

Lowest-energyrule

最低能量原理:電子在核外排列應(yīng)盡先分布在低能級軌道上,使整個原子系統(tǒng)能量最低。Pauliexclusionprinciple

保里不相容原理:在同一原子中,不可能存在所處狀態(tài)完全相同的電子。Hund’srule

洪特規(guī)則:在能量相同（n和l相同）的軌道上分布的電子,將盡先占據(jù)不同的軌道,且自旋平行。56應(yīng)用核外電子填入軌道順序圖，根據(jù)保里不相容原理、能量最低原理、洪特規(guī)則，可以寫出元素原子的核外電子分布式。如19K1s22s22p63s23p64s1

26Fe1s22s22p63s23p63d64s2

核外電子填入軌道的順序正確書寫是從內(nèi)層到外層書寫，將同一層電子放在一起，（可與填充順序不一致。）57Figure8-10Orbitaldiagramsfornitrogenatom.58Electronconfigurations

N:1s22s22p3,1s22s22px12py12pz159Abbreviatedelectronconfigurations

原子實(shí)+最高能級組26Fe:1s22s22p63s23p63d64s2

Fe:[Ar]3d64s229Cu:1s22s22p63s23p63d104s1

Cu:[Ar]3d104s1(not[Ar]3d94s2）33As:1s22s22p63s23p63d104s24p3

As:[Ar]3d104s24p360Valenceelectronconfigurations

Valenceelectronsrefertoelectronsthatinvolveinbondformation.Theorbitalsthatoccupiedbyvalenceelectronsarecalledvalenceorbitals.

Foratomsofthemain-groupelements,theirvalenceelectronsaretheelectronswiththeoutmostprincipalquantumnumber.Forthetransitionmetals,theirvalenceelectronsaretheelectronsinthehighestgroupoforbitalenergy,forexample,thevalenceelectronconfigurationforironatomis3d64s2.61valenceelectronconfigurationFe2+is3d6Fe3+is3d5Forthetransitionmetals,theirvalenceelectronsaretheelectronsinthehighestgroupoforbitalenergy,forexample,thevalenceelectronconfigurationforironatomis3d64s2.62Pd:4d10insteadof4d85s2;Pt:5d96s1not5d86s2.63元素周期律：元素以及由它形成的單質(zhì)和化合物的性質(zhì)，隨著元素的原子序數(shù)(核電荷數(shù))的依次遞增，呈現(xiàn)周期性的變化。642-3ThePeriodicTableandtheElectronConfigurations

Period(周期),Group（族），

Block（區(qū)）65Table8-4TheCorrespondingRelationshipbetweenthePeriod

inPeriodicTableandtheAtomicEnergyLevelGroup

Periods

GroupsofOrbitalEnergyLevels

NumbersoforbitalsMaximumNumbersofElectronsAccommodated=Numbersofelements

Types1I(1s)12supershort2II(2s2p)48short3III(3s3p)48short4IV(4s3d4p)918long5V(5s4d5p)918long6VI(6s4f5d6p)1632superlong7VII(7s5f6d7p)1632(notfinished)

notfinished

8VIII(8s5g6f7d8p)2550(119~168)-9IX(9s6g7f8d9p)2550(169~218)-66ThegroupslabeledIA,IIA,IIIA,IVA,VA,VIA,VIIA,VIIIA(somePeriodicTableuse0insteadofVIIIA,Seeappendix6.)arecalledmain-group,orrepresentative,elements.Everymemberofthesegroupshasthesamevalenceelectronconfiguration,andvalenceelectronsaretheelectronsintheoutmostshell.ThegroupslabeledIIIB,IVB,VB,VIB,VIIB,VIII(VIIIgroupoccupyingthreeverticallines),IB,IIB,arecalledtransition-metalgroups.Themain-groupscontainbothshortperiodsandlongperiods;thetransition-metalgroupscontainonlylongperiods.675-3-5元素周期系與核外電子分布的關(guān)系ⅠA0一1ⅡAⅢAⅣAⅤAⅥAⅦA2二345678910三1112ⅢBⅣBⅤBⅥBⅦBⅧⅠBⅡB131415161718四192021222324252627282930313233343536五373839404142434445464748495051525354六555657*727374757677787980818283848586七878889*104105106107108109110111112元素周期系與核外電子分布的關(guān)系鑭系575859606162636465666768697071錒系8990919293949596979899100101102103Sddspfns1~2

(n-1)d1~9ns1~2(n-1)d10ns1~2ns2np1~6(n-2)f0~14(n-1)d0~2ns268Example8-3Writetheelectronconfiguration,name,symbolandatomicnumberforanelementinthefifthperiodandGroupVA.SOLUTIONElectronconfiguration:36[Kr]4d105s25p3

Z=51,Sb,Antimony(Stibium).69Example8-4Theatomicnumberis23.Writeitselectronconfiguration,valenceelectronconfiguration,andpointoutitsposition.SOLUTION23Zelectronconfiguration:1s22s22p63s23p63d34s2,valenceelectronconfiguration:3d34s2,Thereforethiselementisatthefourthperiod,GroupVB.ItisV.703PeriodicTrendinAtomicProperties

3-1AtomicRadius

CovalentatomicradiiMetallicradiiVanderWaalsradii

71共價半徑=兩個相同原子形成共價鍵時，其核間距離的一半。定義d=198pmr(Cl)=99pmd=154pmr(C)=77pm72金屬半徑=金屬單質(zhì)晶體中，兩個相鄰金屬原子核間距離的一半。定義d=256pmr(Cu)=128pm73主族元素：從左到右r減小；從上到下r增大。過渡元素：從左到右r緩慢減??；

從上到下r

略有增大。He50Ne160Ar191Kr198Xe21774解釋:

電子層數(shù)不變的情況下,有效核電荷的增大導(dǎo)致核對外層電子的引力增大.

主族元素:電子逐個填加在最外層,對原來最外層上的電子的屏蔽參數(shù)(σ)小,有效核電荷(Z*)迅速增大。

副族元素:電子逐個填加在次外層,增加的次外層電子對原來最外層上電子的屏蔽較強(qiáng),有效核電荷增加較小。753-2IonizationEnergyMg(g)=Mg+(g)+e-

I1=738kJ?mol-1Mg+(g)=Mg2+(g)+e-

I2=1445kJ?mol-1

Mg2+(g)=Mg3+(g)+e-

I3=7730kJ?mol-1firstionizationenergy,I1secondionizationenergy,I2thirdionizationenergy,I

3.I

1<I

2<I3

76N、P、As、Sb、Be、Mg電離能較大

——半滿，全滿。同周期總趨勢：自左至右I1逐漸增大,與原子半徑減小的趨勢相對應(yīng).同族總趨勢：自上至下I1減小,與原子半徑增大的趨勢是對應(yīng)的.773-3ElectronAffinity

A(g)+e-→A-(g)E1A-(g)+e-=A2-(g)E2電子親合能正負(fù)號的規(guī)定與焓的正負(fù)號規(guī)定相反，即放熱為正，吸熱為負(fù)。電子親合能用來衡量氣態(tài)原子得電子的難易:電子親合能越大,原子越易得到電子;電子親合能越小,原子越難得到電子.78Figure8-12Firstionizationenergyandelectronaffinityasafunctionofatomicnumber.793-4Electronegativity

Electronegativityrepresentstheabilityofanatomina