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
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