大学化学课件-国外原版教材.ppt

Copyright1999,PRENTICEHALL,Chapter2,1,Atoms,Molecules,andIons,Chapter2,DavidP.WhiteUniversityofNorthCarolina,Wilmington,Copyright1999,PRENTICEHALL,Chapter2,2,JohnDalton:EachelementiscomposedofatomsAllatomsofanelementareidentical.Inchemicalreactions,theatomsarenotchanged.Compoundsareformedwhenatomsofmorethanoneelementcombine.Daltonslawofmultipleproportions:Whentwoelementsformdifferentcompounds,themassratiooftheelementsinonecompoundisrelatedtothemassratiointheotherbyasmallwholenumber.,TheAtomicTheoryofMatter,Copyright1999,PRENTICEHALL,Chapter2,3,TheancientGreekswerethefirsttopostulatethatmatterconsistsofindivisibleconstituents.Laterscientistsrealizedthattheatomconsistedofchargedentities.CathodeRaysandElectronsAcathoderaytube(CRT)isahollowvesselwithanelectrodeateitherend.Ahighvoltageisappliedacrosstheelectrodes.,TheDiscoveryofAtomicStructure,Copyright1999,PRENTICEHALL,Chapter2,4,CathodeRaysandElectronsThevoltagecausesnegativeparticlestomovefromthenegativeelectrodetothepositiveelectrode.Thepathoftheelectronscanbealteredbythepresenceofamagneticfield.,TheDiscoveryofAtomicStructure,Copyright1999,PRENTICEHALL,Chapter2,5,CathodeRaysandElectronsConsidercathoderaysleavingthepositiveelectrodethroughasmallhole.Iftheyinteractwithamagneticfieldperpendiculartoanappliedelectricfield,thecathoderayscanbedeflectedbydifferentamounts.Theamountofdeflectionofthecathoderaysdependsontheappliedmagneticandelectricfields.Inturn,theamountofdeflectionalsodependsonthechargetomassratiooftheelectron.,TheDiscoveryofAtomicStructure,Copyright1999,PRENTICEHALL,Chapter2,6,CathodeRaysandElectrons,TheDiscoveryofAtomicStructure,Copyright1999,PRENTICEHALL,Chapter2,7,CathodeRaysandElectronsIn1897,Thomsondeterminedthechargetomassratioofanelectrontobe1.76108C/g.Goal:findthechargeontheelectrontodetermineitsmass.,TheDiscoveryofAtomicStructure,Copyright1999,PRENTICEHALL,Chapter2,8,CathodeRaysandElectronsConsiderthefollowingexperiment:Oildropsaresprayedaboveapositivelychargedplatecontainingasmallhole.Astheoildropsfallthroughthehole,theyaregivenanegativecharge.Gravityforcesthedropsdownward.Theappliedelectricfieldforcesthedropsupward.Whenadropisperfectlybalanced,theweightofthedropisequaltotheelectrostaticforceofattractionbetweenthedropandthepositiveplate.,TheDiscoveryofAtomicStructure,Copyright1999,PRENTICEHALL,Chapter2,9,CathodeRaysandElectrons,TheDiscoveryofAtomicStructure,Copyright1999,PRENTICEHALL,Chapter2,10,CathodeRaysandElectronsUsingthisexperiment,Millikandeterminedthechargeontheelectrontobe1.6010-19C.Knowingthechargetomassratio,1.76108C/g,Millikancalculatedthemassoftheelectron:9.1010-28g.Withmoreaccuratenumbers,wegetthemassoftheelectrontobe9.1093910-28g.,TheDiscoveryofAtomicStructure,Copyright1999,PRENTICEHALL,Chapter2,11,RadioactivityConsiderthefollowingexperiment:Aradioactivesubstanceisplacedinashieldcontainingasmallholesothatabeamofradiationisemittedfromthehole.Theradiationispassedbetweentwoelectricallychargedplatesanddetected.Threespotsarenotedonthedetector:aspotinthedirectionofthepositiveplate,aspotwhichisnotaffectedbytheelectricfield,aspotinthedirectionofthenegativeplate.,TheDiscoveryofAtomicStructure,Copyright1999,PRENTICEHALL,Chapter2,12,Radioactivity,TheDiscoveryofAtomicStructure,Copyright1999,PRENTICEHALL,Chapter2,13,RadioactivityAhighdeflectiontowardsthepositiveplatecorrespondstoradiationwhichisnegativelychargedandoflowmass.Thisiscalledb-radiation(consistsofelectrons).Nodeflectioncorrespondstoneutralradiation.Thisiscalledg-radiation.Smalldeflectiontowardsthenegativelychargedplatecorrespondstohighmass,positivelychargedradiation.Thisiscalleda-radiation.,TheDiscoveryofAtomicStructure,Copyright1999,PRENTICEHALL,Chapter2,14,TheNuclearAtomFromtheseparationofradiationweconcludethattheatomconsistsofneutral,positively,andnegativelychargedentities.Thomsonassumedallthesechargedspecieswerefoundinasphere.,TheDiscoveryofAtomicStructure,Copyright1999,PRENTICEHALL,Chapter2,15,TheNuclearAtomRutherfordcarriedoutthefollowingexperiment:Asourceofa-particleswasplacedatthemouthofacirculardetector.Thea-particleswereshotthroughapieceofgoldfoil.Mostofthea-particleswentstraightthroughthefoilwithoutdeflection.Somea-particlesweredeflectedathighangles.IftheThomsonmodeloftheatomwascorrect,thenRutherfordsresultwasimpossible.,TheDiscoveryofAtomicStructure,Copyright1999,PRENTICEHALL,Chapter2,16,TheNuclearAtomRutherfordsa-particleexperiment:,TheDiscoveryofAtomicStructure,Copyright1999,PRENTICEHALL,Chapter2,17,TheNuclearAtomInordertogetthemajorityof-particlesthroughapieceoffoiltobeundeflected,themajorityoftheatommustconsistofalowmass,diffusenegativecharge-theelectron.Toaccountforthesmallnumberofhighdeflectionsofthe-particles,thecenterornucleusoftheatommustconsistofadensepositivecharge.,TheDiscoveryofAtomicStructure,Copyright1999,PRENTICEHALL,Chapter2,18,TheNuclearAtomRutherfordmodifiedThomsonsmodelasfollows:assumetheatomissphericalbutthepositivechargemustbelocatedatthecenter,withadiffusenegativechargesurroundingit.,TheDiscoveryofAtomicStructure,Copyright1999,PRENTICEHALL,Chapter2,19,Theatomconsistsofpositive,negative,andneutralentities(protons,electrons,andneutrons).Protonsandneutronsarelocatedinthenucleusoftheatom,whichissmall.Mostofthemassoftheatomisduetothenucleus.Therecanbeavariablenumberofneutronsforthesamenumberofprotons.Isotopeshavethesamenumberofprotonsbutdifferentnumbersofneutrons.Electronsarelocatedoutsideofthenucleus.Mostofthevolumeoftheatomisduetoelectrons.,TheModernViewofAtomicStructure,Copyright1999,PRENTICEHALL,Chapter2,20,TheModernViewofAtomicStructure,Copyright1999,PRENTICEHALL,Chapter2,21,TheModernViewofAtomicStructure,Copyright1999,PRENTICEHALL,Chapter2,22,Isotopes,AtomicNumbers,andMassNumbersAtomicnumber(Z)=numberofprotonsinthenucleus.Massnumber(A)=totalnumberofnucleonsinthenucleus(i.e.,protonsandneutrons).Byconvention,forelementX,wewriteIsotopeshavethesameZbutdifferentA.,TheModernViewofAtomicStructure,Copyright1999,PRENTICEHALL,Chapter2,23,Isotopes,AtomicNumbers,andMassNumbers,TheModernViewofAtomicStructure,Copyright1999,PRENTICEHALL,Chapter2,24,ThePeriodicTableisusedtoorganizethe114elementsinameaningfulway.Asaconsequenceofthisorganization,thereareperiodicpropertiesassociatedwiththeperiodictable.,ThePeriodicTable,Copyright1999,PRENTICEHALL,Chapter2,25,Columnsintheperiodictablearecalledgroups(numberedfrom1Ato8Aor1to18).Rowsintheperiodictablearecalledperiods.Metalsarelocatedonthelefthandsideoftheperiodictable(mostoftheelementsaremetals).Non-metalsarelocatedinthetoprighthandsideoftheperiodictable.Elementswithpropertiessimilartobothmetalsandnon-metalsarecalledmetalloidsandarelocatedattheinterfacebetweenthemetalsandnon-metals.,ThePeriodicTable,Copyright1999,PRENTICEHALL,Chapter2,26,ThePeriodicTable,Copyright1999,PRENTICEHALL,Chapter2,27,Someofthegroupsintheperiodictablearegivenspecialnames.Thesenamesindicatethesimilaritiesbetweengroupmembers:Group1A:Alkalimetals.Group2A:Alkalineearthmetals.Group6A:Chalcogens.Group7A:Halogens.Group8A:Noblegases.,ThePeriodicTable,Copyright1999,PRENTICEHALL,Chapter2,28,MoleculesandChemicalFormulasMoleculesareassembliesoftwoormoreatomsbondedtogether.Eachmoleculehasachemicalformula.Thechemicalformulaindicateswhichatomsarefoundinthemolecule,andinwhatproportiontheyarefound.Compoundsformedfrommoleculesaremolecularcompounds.,MoleculesandMolecularCompounds,Copyright1999,PRENTICEHALL,Chapter2,29,MolecularandEmpiricalFormulasMolecularformulasgivetheactualnumbersandtypesofatomsinamolecule.Examples:H2O,CO2,CO,CH4,H2O2,O2,O3,andC2H4.Empiricalformulasgivetherelativenumbersandtypesofatomsinamolecule.Thatis,theygivethelowestwholenumberratioofatomsinamolecule.Examples:H2O,CO2,CO,CH4,HO,CH2.,MoleculesandMolecularCompounds,Copyright1999,PRENTICEHALL,Chapter2,30,PicturingMoleculesMoleculesoccupythreedimensionalspace.However,weoftenrepresentthemintwodimensions.Thestructuralformulagivestheconnectivitybetweenindividualatomsinthemolecule.Thestructuralformulamayormaynotbeusedtoshowthethreedimensionalshapeofthemolecule.,MoleculesandMolecularCompounds,Copyright1999,PRENTICEHALL,Chapter2,31,PicturingMolecules,MoleculesandMolecularCompounds,Copyright1999,PRENTICEHALL,Chapter2,32,MoleculesandMolecularCompounds,PicturingMoleculesIfthestructuralformuladoesshowtheshapeofthemolecule,theneitheraperspectivedrawing,ball-and-stickmodel,orspace-fillingmodelisused.,Copyright1999,PRENTICEHALL,Chapter2,33,Whenanatomormoleculeloseselectrons,itbecomespositivelycharged.Forexample,whenNalosesanelectronitbecomesNa+.Positivelychargedionsarecalledcations.,IonsandIonicCompounds,Copyright1999,PRENTICEHALL,Chapter2,34,Whenanatomormoleculegainselectrons,itbecomesnegativelycharged.ForexamplewhenClgainsanelectronitbecomesCl-.Negativelychargedionsarecalledanions.Anatomormoleculecanlosemorethanoneelectron.,IonsandIonicCompounds,Copyright1999,PRENTICEHALL,Chapter2,35,PredictingIonicChargeThenumberofelectronsanatomlosesisrelatedtoitspositionontheperiodictable.Metalstendtoformcationswhereasnon-metalstendtoformanions.,IonsandIonicCompounds,Copyright1999,PRENTICEHALL,Chapter2,36,IonicCompoundsThemajorityofchemistryinvolvesthetransferofelectronsbetweenspecies.Example:ToformNaCl,theneutralsodiumatom,Na,mustloseanelectrontobecomeacation:Na+.Theelectroncannotbelostentirely,soitistransferredtoachlorineatom,Cl,whichthenbecomesananion:Cl-.TheNa+andCl-ionsareattractedtoformanionicNaCllatticewhichcrystallizes.,IonsandIonicCompounds,Copyright1999,PRENTICEHALL,Chapter2,37,Important:notethattherearenoeasilyidentifiedNaClmoleculesintheioniclattice.Therefore,wecannotusemolecularformulastodescribeionicsubstances.,IonsandIonicCompounds,Copyright1999,PRENTICEHALL,Chapter2,38,IonicCompoundsConsidertheformationofMg3N2:MglosestwoelectronstobecomeMg2+NitrogengainsthreeelectronstobecomeN3-.Foraneutralspecies,thenumberofelectronslostandgainedmustbeequal.However,MgcanonlyloseelectronsintwosandNcanonlyacceptelectronsinthrees.Therefore,Mgneedstolose6electrons(23)andNgainthose6electrons(32).,IonsandIonicCompounds,Copyright1999,PRENTICEHALL,Chapter2,39,IonicCompoundsI.e.,3Mgatomsneedtoform3Mg2+ions(total3x2+charges)and2Natomsneedtoform2N3-ions(total2x3-charges).Therefore,theformulaisMg3N2.,IonsandIonicCompounds,Copyright1999,PRENTICEHALL,Chapter2,40,NamesandFormulasofIonicCompoundsNamingofcompounds,nomenclature,isdividedintoorganiccompounds(thosecontainingC)andinorganiccompounds(therestoftheperiodictable).Cationsformedfromametalhavethesamenameasthemetal.Example:Na+=sodiumion.Ifthemetalcanformmorethanonecation,thenthechargeisindicatedinparenthesesinthename.Examples:Cu+=copper(I);Cu2+=copper(II).Cationsformedfromnon-metalsendin-ium.Example:NH4+ammoniumion.,NamingInorganicCompounds,Copyright1999,PRENTICEHALL,Chapter2,41,NamesandFormulasofIonicCompounds,NamingInorganicCompounds,Copyright1999,PRENTICEHALL,Chapter2,42,NamesandFormulasofIonicCompoundsMonatomicanions(withonlyoneatom)arecalled-ide.Example:Cl-ischlorideion.Exceptions:hydroxide(OH-),cyanide(CN-),peroxide(O22-).Polyatomicanions(withmanyatoms)containingoxygenendin-ateor-ite.(Theonewithmoreoxygeniscalled-ate.)Examples:NO3-isnitrate,NO2-isnitrite.,NamingInorganicCompounds,Copyright1999,PRENTICEHALL,Chapter2,43,NamesandFormulasofIonicCompoundsPolyatomicanionscontainingoxygenwithmorethantwomembersintheseriesarenamedasfollows(inorderofdecreasingoxygen):per-.-ate-ate-itehypo-.-ite,NamingInorganicCompounds,Copyright1999,PRENTICEHALL,Chapter2,44,NamesandFormulasofIonicCompounds,NamingInorganicCompounds,Copyright1999,PRENTICEHALL,Chapter2,45,NamesandFormulasofIonic