考研专业英语化学

ChemistryEnglishfo[e-mail]•Ionsareelectricallychargedspeciesformedwhenaneutralatomeithergainsorlosesoneormoreelectrons.•Cations,orpositiveions,formwhenatomsloseoneormoreelectrons.•Anions,ornegativeions,formwhenatomsgainoneormoreelectrons.1.FormationofIons•twophysicalproperties,meltingpointandtheabilitytoconductelectricity.•IonicCompoundshaveveryhighmeltingpointandaregoodconductorsofelectricitywhentheyareeithermeltedordissolvedinwater.•Covalentcompoundshavemuchlowermeltingpointandarepoorconductorsofelectricity.2.ClassificationofCompounds3.IonicCompounds•anelectricallyneutralcompoundwhichconsistsofcationsandanions•heldtogetherbyforcesofelectricattraction.•Thenameforanioniccompound:thenameofthecationfollowedbythenameoftheanion.•Sodiumchloride:NaCl=Na++Cl-•MagnesiumChloride:MgCl2=Mg2++2Cl-•Bariumphosphate:Ba3(PO4)2FormulaNameFormulaNameF-fluorideO2-oxideCl-chlorideO22-peroxideClO-HypochloriteS2-sulfideClO2-ChloriteSO32-sulfiteClO4-perchlorateSO42-sulfateBr-bromideHSO4-bisulfateI-IodideSCN-thiocyanateH-hydrideSe2-selenideOH-hydroxideCrO42-chromateCN-cyanideCr2O72-dichromateN3-nitrideCO32-carbonateNO2-nitriteHCO3-bicarbonateNO3-NitratePO43-phosphateMnO4-permanganateHPO42-hydrogenphosphateC4-carbideH2PO4-dihydrogenphosphate4.CommonanionsandtheirnamesFormulaNameFormulaNameAl3+aluminumFe2+iron(II)NH4+ammoniumFe3+iron(III)Ba2+bariumPb2+lead(II)Cd2+cadmiumLi+lithiumCa2+calciumMg2+magnesiumCs+cesiumMn2+manganese(II)Cr3+chromium(III)Hg2+mercury(II)Co2+cobalt(II)Hg22+mercury(I)Cu+copper(I)Ag+silverCu2+copper(II)Sn2+tin(II)H+hydrogenTi4+titanium(IV)K+potassiumZn2+zincNa+sodiumSr2+strontium5.Commoncationsandtheirnames6.NamesofsomecovalentbinarycompoundsFormulaPropernameTrivialnameCOCarbonmonoxideCO2CarbondioxideNONitrogenoxideNitricoxideNO2NitrogendioxideN2ODinitrogenoxideNitrousoxideSO2SulfurdioxideNH3NitrogentrihydrideammoniaH2ODihydrogenoxidewaterSO3SulfurtrioxideCH4Carbontetrahydridemethaneyxzyxzyxzyxzsorbitalpxorbitalpzorbitalpyorbital•Anorbitalisaregioninwhichthereisahighprobabilityoffindinganelectron.•sorbitalisspherical.•porbitalsaredumbbell-shaped.7.Shapesofatomicorbitals•Eachelectroninanatompossessesatotalenergy(kineticpluspotential).Thelowest-energyelectronsarethoseclosesttothenucleusoftheatomandthemostdifficulttoremovefromtheatom.•Theenergylevelforanelectronisthesumofitskineticandpotentialenergy.8.ElectronicConfigurations9.WritingElectronicConfigurationsforAtoms•Theelectronicconfigurationsforanatomiswrittenbylistingtheorbitalsoccupiedbyelectronsintheatomalongwiththenumberofelectronsineachorbitals.•ThreeRuleswhichmustbefollowedinwritingelectronicconfigurationsarePauliprinciple,Aufbauprinciple,andHund’srule.•Eachorbitalmaycontaintwoelectrons.Itispossibleforanorbitaltocontainnoelectronsorjustoneelectron,butnomorethantwoelectrons.PauliPrincipleAufbauPrinciple•Orbitalsarefilledbystartingwiththelowest-energyorbitalsfirst.Forexample,1sorbitalsarefilledbefore2sorbitalswhichinturnarefilledbefore2porbitals.•Whenorbitalsofequalenergy,suchasthethreeporbitals,arebeingfilled,electronstendtohavethesamespin.Theelectronsoccupydifferentorbitalssoastoremainasfarapartaspossible.Thisisreasonable,sinceelectronshavelikechargesandtendtorepeleachother.Theelectronsdonotpairupuntilthereisatleastoneelectronineachoftheequal-energyorbitals.•e.g.,2p4,pxpypz.Hund’sPrincipleExamplesofElectronicConfigurationsofAtoms•H)1s1or1s.•He)1s2or1s•B)1s22s22px1or2px2py2pz.2s1s•C)1s22s22px12py1or2px2py2pz.2s1sQuiz2•Writetheelectronicconfigurationforfluorineandcopper.2ChemicalBonding2.1Introduction•Chemicalbonds:theattractiveforcesthatjoinatoms.•thedistancebetweenthecentersoftwoatomsisbetween70pmand300pm.•Bondenergy:Theenergyneededtobreakachemicalbondbetweentwoatoms•Classification:convenientlydividedintotwobroadclasses,ionicandcovalentcompounds.2.6CovalentBondingTheories•Acovalentbondbetweentwoatomsisformedbysharingofoneormorepairsofelectrons.•Unlikeanionicbond,formationofwhichinvolvesatransferofelectrons.•Usingthemodernorbitalpictureoftheatom,onecanexplainhowacovalentbondforms.CovalentbondinginH2•AHatomhasa1sorbitalcontainingoneelectron.•WhentwoHatomsgetcloserandcloser,their1sorbitalbegintooverlap.•Thetwo1sorbitalmergetoformamolecularorbitalofincreasedelectrondensity.•ThetwoelectronsinthemolecularorbitalaresharedbytwoHatoms.yxzyxzyxzyxzsorbitalpxorbitalpzorbitalpyorbital•Anorbitalisaregioninwhichthereisahighprobabilityoffindinganelectron.•sorbitalisspherical.•porbitalsaredumbbell-shaped.classificationofcovalentbondsShapesofatomicorbitals•Sigma()MOsformfromtheoverlapofswithsandpwithsandfromthehead-to-headoverlapoftwoorbitals.•Thepi(p)MOsformfromtheside-to-sideoverlapoftwoporbitals.s+ss+pp+pp+pbond(s)pbondclassificationofcovalentbonds2.7LewisElectronDotStructures•AnamericanchemistG.N.Lewisdescribesacovalentbondasasharedpairofelectrons.•TheLewistheorypredictsthelikelihoodofformationofcovalentmoleculesbyestablishingacriterionfortheirstability.•Thecriterionisthatanelect