chapter5-ChemicalPeriodicity(化学周期性)

5ChemicalPeriodicity化学周期性ThereactionofH2OandLi(left)toproduceLiOHandH2(g)ismuchslowerthantheanalogousreactionbetweenH2OandNa(right).ChapterGoals5-1MoreAboutthePeriodicTablePeriodicPropertiesoftheElements元素的周期特质5-2AtomicRadii原子半径5-3IonizationEnergy游离能5-4ElectronAffinity电子亲和力5-5IonicRadii离子半径5-6Electronegativity电负性5-7OxidationStatesChemicalReactionsandPeriodicity5-7Hydrogen&theHydrides•Hydrogen•ReactionsofHydrogenandtheHydrides5-8Oxygen&theOxides•OxygenandOzone•ReactionsofOxygenandtheOxides•CombustionReactions•CombustionofFossilFuelsandAirPollution2MoreAboutthePeriodicTable•Establishaclassificationschemeoftheelementsbasedontheirelectronconfigurations.–NobleGases钝气Group8A•Allofthemhavecompletelyfilledelectronshells.•Sincetheyhavesimilarelectronicstructures,theirchemicalreactionsaresimilar.ns2np6He1s2Ne[He]2s22p6Ar[Ne]3s23p6Kr[Ar]4s23d104p6Xe[Kr]5s24d105p6Rn[Xe]6s24f145d106p63MoreAboutthePeriodicTable–RepresentativeElements典型元素•AretheelementsinAgroupsonperiodicchart.•Theseelementswillhavetheir“last”electroninanoutersorporbital.•Theseelementshavefairlyregularvariationsintheirproperties.4MoreAboutthePeriodicTable•d-TransitionElements过渡金属元素–ElementsonperiodicchartinBgroups.–Sometimescalledtransitionmetals.•Eachmetalhasdelectrons.–ns(n-1)dconfigurations•Theseelementsmakethetransitionfrommetalstononmetals.•Exhibitsmallervariationsfromrow-to-rowthantherepresentativeelements.5Firsttransitionseries(4sand3dorbitaloccupy):21Scthrough30ZnSecondtransitionseries(5sand4dorbitaloccupy):39Scthrough48CdThirdtransitionseries(6sand5dorbitaloccupy):52Laand72Hfto80HgFourthtransitionseries(6sand5dorbitaloccupy):89Acand104Rfto112MoreAboutthePeriodicTable•f-transitionmetals–Sometimescalledinnertransitionmetals.–Electronsarebeingaddedtoforbitals.6Outermostelectronshavethegreatestinfluenceonthechemicalpropertiesofelements.•Addinganelectrontoansorporbitaldramaticchangeinthephysicalandchemicalproperties•AddinganelectrontoadorforbitalmuchsmallereffectonpropertiesPeriodicPropertiesoftheElementsAtomicRadii原子半径IonizationEnergy游离能ElectronAffinity电子亲和力IonicRadii离子半径Electronegativity电负性78AtomicRadii原子半径relativesizesAtomicradiiincreaseAtomicradiidecreaseÅ=10-10m同周期典型元素大致随原子序增加→原子半径愈小同族元素原子序增加原子半径愈大AtomicRadii•Thereasontheatomicradiidecreaseacrossaperiodisduetoshieldingorscreeningeffect屏蔽效应.–Effectivenuclearcharge有效核电荷,Zeff,experiencedbyanelectronislessthantheactualnuclearcharge,Z.–最外层电子受原子的吸引力被内层电子对外层电子的排斥力给抵销即称屏蔽效应•Movingacrossaperiod,eachelementhasanincreasednuclearchargeandtheelectronsaregoingintothesameshell(2sand2por3sand3p,etc.).–Consequently,theouterelectronsfeelastrongereffectivenuclearcharge.–ForLi,Zeff~+1ForBe,Zeff~+29有效核电荷镁的有效核电荷约为12–10=2原子核质子数－内层电子数总和•原子半径随原子序数的增加呈现周期性变化。这与原子有效核电荷的周期性变化相关–因为有效核电荷愈大,对外层电子的吸引力愈大,原子半径就愈小•各周期的主族从左到右,电子层数不变,有效核电荷增加明显,原子半径的逐渐减少也就比较明显•长周期中的过渡元素原子半径先是缓慢缩小然后略有增大•内过渡元素，有效核电荷变化不大，原子半径几乎不变•稀有气体原子半径突然增大，因为它是vanderWaals半径•同一主族从上到下，由于电子层数增加，使遮罩效应明显加大，所以原子半径递增。11凡得瓦半径为两个相邻非键结原子间距离的一半AtomicRadii•Example5-1:Arrangetheseelementsbasedontheiratomicradii.–Se,S,O,Te–P,Cl,S,Si–Ga,F,S,As–Cs,F,K,Cl6AOSSeTePeriod3ClSPSiFSAsGaFClKCs12AtomicradiiincreaseAtomicradiidecreaseIonizationEnergy游离能•Firstionizationenergy(IE1)第一游离能–Theminimumamountofenergyrequiredtoremovethemostlooselyboundelectronfromanisolatedgaseousatomtoforma1+ion处于基态的气态原子失去一个电子，成为＋1价气态阳离子，所需吸收的能量•Symbolically:Atom(g)+energyion+(g)+e-13Mg(g)+738kJ/molMg++e-IonizationEnergy•Secondionizationenergy(IE2)第二游离能–Theamountofenergyrequiredtoremovethesecondelectronfromagaseous1+ion.•Symbolically:ion++energyion2++e-14Mg++1451kJ/molMg2++e-•Atomscanhave3rd(IE3),4th(IE4),etc.ionizationenergies.IonizationEnergyPeriodictrendsforIonizationEnergy:1.IE2IE1Italwaystakesmoreenergytoremoveasecondelectronfromanionthanfromaneutralatom.2.IE1generallyincreasesmovingfromIAelementstoVIIIAelements.ImportantexceptionsatBe&Mg,N&P,etc.duetofilledandhalf-filledsubshells.3.IE1generallydecreasesmovingdownafamily.IE1forLiIE1forNa,etc.15Decreaseincrease随原子序增大渐增趋势随原子序增大而递减同一族元素的游离能•随原子序的增加而变小•例如第1族元素的第一游离能大小顺序为：LiNaKRbCsFr•同族元素的原子序愈大，原子半径愈大，最外壳层电子受原子核的引力愈小，故电子愈容易移除。游离能的周期性•同一周期之各元素的第一游离能，随原子序的增加，呈现锯齿状的增加•原子半径愈小，且有效核电荷愈大，所需的IE愈大•同一周期第一游离–2族3族，镁(738kJ/mol)铝(578kJ/mol)–15(5A)16(6A)，磷(1012kJ/mol)硫(1000kJ/mol)•同一周期过渡元素，因原子半径及有效核电荷彼此差异不大，故其第一游离能彼此差异相对较小游离能的规则同一周期元素的第一游离能从左至右渐增,但在中间有些起伏IIAIIIA,而VAVIA:•IIA(ns2)IIIA(ns2np1)是因为np能阶较ns高,因此IIIA原子的游离能较小•VA(ns2np3)VIA(ns2np4)•因为VA族的价电子组态为全半填满,而VIA族有一个p轨域填入两个电子,将增加电子的斥力,因此较易移去,故VAVIA19FirstIonizationEnergiesofSomeElements20Elementswithlowionizationenergies(IE)easilylosetoformcations(positivecharge)IonizationEnergy•Example5-2:Arrangetheseelementsbasedontheirfirstionizationenergies.–Sr,Be,Ca,Mg–Al,Cl,Na,P–B,O,Be,N–Na,Mg,Al,SiSrCaMgBeNaAlPClBBeONNaAlMgSi21DecreaseincreaseIonizationEnergy•First,second,third,etc.ionizationenergiesexhibitperiodicityaswell•Lookatthefollowingtableofionizationenergiesversusthirdrowelements–Noticethattheenergyincreasesenormouslywhenanelectronisremovedfromacompletedelectronshell22GroupandelementIANaI