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[物理学类]

题目序号题型归类

第1题中心主旨题型

第2题段落关系题型

第3题审题定位题型

第4题句间关系与反推题型

第5题审题定位题型

Oneofthesimplestandbestknownkindsofcrystalistheionicsalt,ofwhichatypicalexampleissodiumchloride,orordinarytablesalt.Thefundamentalcomponentsofanionicsaltareions:atomsormoleculesthathavebecomeelectricallychargedbygainingorlosingonemoreelectrons.Informingsodiumchloride,forexample,sodiumatomsgiveupanelectron(therebybecomingpositivelycharged)andchlorineatomsgainanelectron(therebybecomingnegativelycharged).Theionsareattractedtooneanotherbytheiroppositecharges,andtheystacktogethercompactly,liketightlypackedspheres.

Recently,scientistsatMichiganStateUniversitycreatedanewkindofcrystalcalledanelectride.Inelectrides,theanions(negativeions)arecompletelyreplacedbyelectrons,whicharetrappedinnaturallyformedcavitieswithinaframeworkofregularlystackedcations(positiveions).Electridesarethefirstexamplesofionicsaltsinwhichalltheseanionicsitesareoccupiedsolelybyelectrons.

Unlikeothertypesofanions,anionicelectronsdonotbehaveasiftheyweresimplechargedspheres.Inparticular,becauseoftheirlowmassandtheirtendencytointeractwithoneanotherovergreatdistances,theycannotbe“pinneddown”toanyonelocation.Instead,theywanderclosetoandamongtheatomsliningthecavityandinteractwithelectronsinnearbycavities,perhapschangingplaceswiththem.

Thepropertiesofanelectridedependlargelyonthedistancebetweenthecavitiesthatholdtrappedelectrons.Whenthetrappedelectronsarefarapart,theydonotinteractstrongly,andsobehavesomewhatlikeanarrayofisolatednegativecharges.Whentheyareclosertogether,theybegintodisplaypropertiesassociatedwithlargeensemblesofidenticalparticles.Whentheyarestillcloser,theensemblepropertiesdominateandtheelectrons“delocalize”:theyarenolongertightlyboundwithinindividualcavitiesbutaremoreorlessfreetopassthroughthespaceswithintheframeworkofpositiveions.

Bysynthesizingelectridesfromavarietyofmaterials,onecanvarythegeometryoftheanioniccavitiesandtheirrelationtothesurroundingcations.Theresultingpropertiesmaymakeitpossibleforelectridestobecomeabasisforeconomicallyusefulnewmaterialsanddevices.Forinstance,becausetheelectronsinsomeelectridesareveryweaklybound,thesecrystalscouldbeeffectiveasphotosensitivedetectors,inwhichanimpingingphotonliberatesanelectron,resultinginasmallelectriccurrent.Thesameweakbindingcouldalsomakeelectridesusefulinsolarenergyconvertersandascathodesinbatteries.Oneobstacleisthetendencyofelectridestodecomposethroughreactionwithairandwater.Researchersareseekingwaystoincreasetheirstability.

1.Thetextisprimarilyconcernedwithdiscussing

[A]awaytoisolateelectrons.

[B]thecharacteristicsofanewkindofcrystal.

[C]thestructureofanionicsalt.

[D]commercialusesforelectrides.

2.Inthefirstparagraph,theauthorisprimarilyconcernedwith

[A]introducingavariantonthestandardatomictheory.

[B]describinghowchlorineatomscanbecomenegativelycharged.

[C]describingsomeearlyresearchatMichiganStateUniversity.

[D]providingbackgroundforthetechnicaldiscussiontofollow.

3.Accordingtothetext,thedefiningcharacteristicofanelectrideiswhichofthefollowing?

[A]Itspositiveareofparticularlylowmass.

[B]Itsionspossessidenticalelectricalcharges.

[C]Itcontainsaframeworkofregularlystackedions.

[D]Itsnegativeionsconsistsolelyofelectrons.

4.Itcanbeinferredfromthetextthatanionsbehavingas“simplechargedspheres”(line2,paragraph3)couldbeexpectedto

[A]readilyloseelectronsandbecomepositivelycharged.

[B]movefreelyinandoutoftheircavities.

[C]respondtophotonsbyliberatingelectrons.

[D]remainfixedrelativetotheircations.

5.Withwhichofthefollowingstatementsregardingelectrideswouldtheauthormostlikelyagree?

[A]Theyhaveproventhemselvestobeofgreatcommercialvalue.

[B]Theirfuturecommercialvalueispromisingbutuncertain.

[C]Theyareinterestingbutofnopracticalvalue.

[D]Theyhavecommercialvaluemainlyinsolarenergyapplications.