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1、第八章Themostpopularformoftheperiodictableisthelongformthatisfoundinsidethebackcoverofthisbook.Theperiodsconsistofthoseelementsthatarearrangedinhorizontalrowsinthetable.Theorganizationissuchthatelementsofsimilarchemicalandphysicalproperties(calledgroupsorfamilies)appearinverti
2、calcolumns.Inthistable,thesetofelementsappearingatthebottomandcalledthelanthanidesshouldactuallyappearinthebodyofthechartinproperorderbyatomicnumbersothatthesixthperiodhasitsrequisite32elements.Forconvenienceinreproductionthisisnotdone;but,properly,thechartshouldbeverticall
3、ycut,thesectionsseparated,andthelanthanidesinsertedintheirproperpositions.Fortheactinides,whichappearbelowthelanthanidesatthebottomoftheperiodictable,thesameconsiderationspertain;theyshouldbeinsertedintheseventhChapter8PeriodicLawandElectronicStructuresl39period(asyetincomp
4、lete).Thefirstperiodconsistsofonlytwoelements,hydrogenandhelium.Subsequentperiodshave8,8,18,18,and32elements.Withtheexceptionofthefirstperiod,eachcompleteperiodbeginswithanalkalimetal(groupⅠA)—ahighlyreactive,light,silverymetal—andendswithanoblegas(group0)—anunreactive,colo
5、rlessgas.Theelementbeforethenoblegasofeachcompleteperiod(again,exceptingthefirstperiod)isahalogen(groupⅦA)—averyreactivenonmetal.Thereisageneralpatternforeachoftheperiodsafterthefirst.Startingwithanalkalimetal,thepropertieschangefromelementtoelement—themetallicpropertiesfad
6、ingandbeinggraduallyreplacedbynonmetalliccharacteristics.Afterahighlyreactivenonmetal,ahalogen,isreached,eachcompleteperiodendswithanoblegas.Sincetheperiodictableclassifiesatomsbychemicalbehavior,andsincechemicalbehaviorisdeterminedbyelectronicconfiguration,theperiodictable
7、mayalsobesaidtoclassifyatomsbyelectronicconfiguration.Themaximumnumberofelectronsthateachenergylevelmayholdisgivenby2n2,wherenistheprincipalquantumnumberoftheshellinquestion.Henceforthen=1shell,themaximumnumberis2(1)2or2;forthen=2level,thisnumberis2(2)2or8;thesemaximumelect
8、ronpopulationsforthefirstfiveshellsaregivenintable8.1.Table8.1MaximumNumberofElect
