AP 化学 ATOMIC THEORYWord文档下载推荐.docx

AP 化学 ATOMIC THEORYWord文档下载推荐.docx

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1978D

ThepostulatesoftheBohrmodelofthehydrogenatomcanbestatedasfollows:

（I）Theelectroncanexistonlyindiscretestateseachwithadefiniteenergy.

（II）Theelectroncanexistonlyincertaincircularorbits.

（III）Theangularmomentumoftheelectronisnh/2wherenisanypositiveinteger.

（IV）Radiationisemittedbytheatomonlywhenanelectronmakesatransitionfromastateofhigherenergytooneoflowerenergy.

（a）Statewhethereachofthesepostulatesiscurrentlyconsideredtobecorrect,accordingtothewavemechanicaldescriptionofthehydrogenatom.

（b）Givethewavemechanicaldescriptionthathasreplacedoneofthepostulatesnowconsideredtobeincorrect.

Answer:

（a）I.CorrectIII.（Correct）*

II.IncorrectIV.Correct

*PostulateIIIisnotcorrectinapreciseinterpretation.Theorbitalangularmomentumisnowindexedbythequantumnumber1ratherthanbyn,theprincipalquantumnumber.However,thepostulateIIIstatementabovedoesnotclearlyidentifynastheprincipalquantumnumber.Perhapsbecauseofthisambiguityandperhapsbecauseofthepresentationinsometexts,candidatescalledpostulateIIIcorrect.TherequirementsofPart（b）forpostulateIII（thatis,givingthewave-modelalternative）isclearlybeyondthescopeofAPChemistry.（TheChiefReaderreportsthatheknowsofnocandidatewholostpointsasaresultofthisinterpretation,whichwasusedinthegrading.）

（b）Thewave-mechanicaldescriptionofpostulateII:

Electron-cloudorchargedistributionincontrastto“orbits”.

Interpretationofelectronlocationintermsofhighprobability.

Sphericaldistributionfors-statesbutnotforothers.Or,electronlocationsstandingwaveswithchargedensitywavesequalto2.

1980D

（a）Writethegroundstateelectronconfigurationforanarsenicatom,showingthenumberofelectronsineachsubshell

（b）GiveonepermissiblesetoffourquantumnumbersforeachoftheoutermostelectronsinasingleAsatomwhenitisinitsgroundstate.

（c）Isanisolatedarsenicatominthegroundstateparamagneticordiamagnetic?

Explainbriefly.

（d）Explainhowtheelectronconfigurationofthearsenicatominthegroundstateisconsistentwiththeexistenceofthefollowingknowncompounds:

Na3As,AsCl3,andAsF5.

（a）1s22s22p63s23p63d104s24p3or

[Ar]3d104s24p3

（b）

n

l

ml

ms

4

-½

oppositespinforselectrons

+½

1

-1

oppositespinforpelectrons

+1

consistentsetofn,l,mlvalues

（c）Paramagnetic.Thereare3unpaired4pelectrons.

（d）AnAsatomcanaccept3e-fromelectropositiveNaatomstogiveAsatomapseudo-Krelectronconfiguration.IonicNa3Asresults.

AnAsatomshare3e-forashareofanelectronfromeachof3Clatomstogetpseudo-KrconfigurationforAsatomincovalentAsCl3.

AnAsatomcanshareall5valenceelectronsbyusing4d-aswellas4sand4p-orbitals（eitherthroughM.O.’sorL.C.A.O.hybrids）togivecovalentAsF5.

1981D

Theemissionspectrumofhydrogenconsistsofseveralseriesofsharpemissionlinesintheultraviolet（Lymanseries）inthevisible（Balmerseries）andintheinfrared（Paschenseries,Brackettseries,etc.）regionsofthespectrum.

（a）Whatfeatureoftheelectronicenergiesofthehydrogenatomexplainswhytheemissionspectrumconsistsofdiscretewavelengthratherthanacontinuumwavelength?

（b）Accountfortheexistenceofseveralseriesoflinesinthespectrum.Whatquantitydistinguishesoneseriesoflinesfromanother?

（c）DrawanelectronicenergyleveldiagramforthehydrogenatomandindicateonitthetransitioncorrespondingtothelineoflowestfrequencyintheBalmerseries.

（d）Whatisthedifferencebetweenanemissionspectrumandanabsorptionspectrum?

ExplainwhytheabsorptionspectrumofatomichydrogenatroomtemperaturehasonlythelinesoftheLymanseries.

（a）Anyofthefollowing:

Quantizedenergylevels.Discreteenergies.

Wavepropertiesofelectronresultindiscreteenergystate.

（b）Anelectroninanexcited-stateatomcangotoanyofseverallowerenergystates.

Thelinesineachseriesrepresentsshiftsfromseveralhigherenergystatestoasinglelowerenergystate,identifiedbythesameprincipalquantumnumberorenergy.

（c）

（d）Emissionspectraobtainedwhenelectronsinexcitedatomsdroptolowerenergylevels.

Absorptionspectraobtainedwhenelectronsinatomsinground（orlowerenergy）stateabsorbelectromagneticradiationandmovetohigherenergystates.

Hatomsat25°

Careinlowestelectronicenergystate（n=1）andsotheonlyabsorptionswillresultfromelectronsmovingfromn=1tohigherlevels.

1983C

AtomicOrbitalsforNAtomicOrbitalsforO

Thediagramaboverepresentsthemolecular-orbitalenergy-leveldiagramfortheNOmolecule.

（a）DrawananalogousdiagramforNO+andoneforNO-.Labelthemolecularorbitals.

（b）Onthebasisofthesediagrams,comparethebondstrengths,thebondlengths,andthebondordersforNO+andNO-.

（c）Which,ifany,ofthesetwospeciesisparamagnetic?

Explainyourreasoning.

（a）NO+,asabove,lessthetopmostelectron.

NO-,asabove,plusanotherunsharedelectron.

（b）Bondorder:

nNO+=3,NO-=2

Or,bondorderforNO+>

bondorderNO-

BondlengthinNO+shorterthaninNO-

BondstrengthinNO+>

bondstrengthinNO-

（c）NO-isparamagneticsince*orbitalsaredegeneratesothatelectronsintheseorbitalsareunpaired.

1984C

Discusssomedifferencesinphysicalandchemicalpropertiesofmetalsandnonmetals.Whatcharacteristicoftheelectronicconfigurationsofatomsdistinguishesmetalsfromnonmetals?

Onthebasisofthischaracteristic,explainwhytherearemanymoremetalsthannonmetals.

Physicalproperties:

metalsnon-metals

meltingpointsrel.highrel.low

elec.conductivitygoodinsulators

lusterhighlittleornone

physicalstatemostsolidsgases,liq.orsolids

[etc.]

Chemicalproperties:

metalsnon-metals

redoxagentsreducingoxid.orreducing

electropositiveelectronegative

oxidesbasicoramphotericacidic

reactwithnonmetalsmetals&

non-metals

Electronconfigurations:

Metals:

Valenceelectronsinsordsublevelsoftheiratoms.（Afewheavyelementshaveatomswithoneortwoelectronsinpsublevels.）Nonmetals:

Valenceelectronsinthesandpsublevelsoftheiratoms.

Therearemoremetalsthannonmetalsbecausefillingdorbitalsinagivenenergylevelinvolvestheatomsoftenelementsandfillingtheforbitalsinvolvestheatomsof14elements.Inthesameenergylevels,themaximumnumberofelementswithatomsreceivingpelectronsissix.

1987D

Usethedetailsofmodernatomictheorytoexplaineachofthefollowingexperimentalobservations.

（a）Withinafamilysuchasthealkalimetals,theionicradiusincreasesastheatomicnumberincreases.

（b）Theradiusofthechlorineatomissmallerthantheradiusofthechlorideion,Cl-.（Radii:

Clatom=0.99Å

;

Cl-ion=1.81Å

）

（c）Thefirstionizationenergyofaluminumislowerthanthefirstionizationenergyofmagnesium.（Firstionizationenergies:

12Mg=7.6ev;

13Al=6.0ev）

（d）Formagnesium,thedifferencebetweenthesecondandthirdionizationenergiesismuchlargerthanthedifferencebetweenthefirstandsecondionizationenergies.（IonizationenergiesforMg:

1st=7.6ev;

2nd=14ev;

3rd=80ev）

（a）Theradiiofthealkalimetalionsincreasewithincreasingatomicnumberbecausetheouterprincipalquantumnumber（orshellorenergylevel）islarger.OR

（1）Thereisanincreaseinshielding.

（2）Thenumberoforbitalsincreases.

（b）Thechlorideionislargerthanthechlorineatombecause-（anyofthese）

（1）theelectron-electronrepulsionincreases.

（2）theelectron-protonratioincreases.

（3）theeffectivenuclearchargedecreases.

（4）shieldingincreases.

（c）ThefirstionizationenergyforMgisgreaterthanthatforAlbecause-（eitherofthese）

（1）the3porbital（Al）representsmoreenergythanthe3sorbital（Mg）represents.

（2）the3pelectroninanAlatomisbettershieldedfromitsnucleusthana3selectroninaMgatom.

（3）[halfcredit]a3pelectroniseasiertoremovethana3selectron.

（d）InaMgatom,thefirsttwoelectronslostareremovedfromthe3sorbitalwhereasthe3rdelectroncomesfroma2porbital;

a2porbitalismuchlowerinenergythanthe3sis;

somoreenergyisneededtoremovea2pelectron.

Twoimportant