Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download 1. Elements in the same family have similar chemical properties
Document related concepts
Transcript
TrendsinthePeriodicTableofTheElements Theperiodictableincluded118elements,92ofwhichoccurnaturally.Eachelementisassigned itsownboxinthetablecontainingthatelement’ssymbol,atomicnumber,atomicmass.Theboxesare arrangedinorderofincreasingatomicnumber. Thehorizontalrowsintheperiodictablearecalledperiodsandthesearenumberedbeginningatthe topfrom1downto7. Eachverticalcolumniscalledafamilyorgroupandthesearelabeledusingoneoftwoschemes.The oldersystemassignseachcolumnanumberfrom1to8combinedwitheithertheletterAorB.Anewer systemsimplynumberseachgroupfrom1to18andusesnoletters. 1. Elementsinthesamefamilyhavesimilarchemicalpropertiesbecausetheyhavesimilar outerelectronconfigurations. 2. Aswemovedownachemicalfamilyoracrossaperiod,thereareregularchangesin thesepropertiescalledperiodictrends. 3. Groups1and2ontheleftand13-18ontherightcontaintherepresentativeofthemain groupelements.Group3-12arethetransitionelements.Withinthetransition elementstherearetwohorizontalseriescollectivelycalledinnertransitionelements. Thefirstseries,knownaslanthanides,fitsbetweenelements56and72inthe6th periodandthesecondseries,calledactinides,fitsbetweenelements88and104inthe 7thperiod. About¾oftheelementsaremetals.Propertiesofmetalsinclude: • • • • • Solidsatroomtemp.exceptforHg Generallyshinyorlustrouswhenfreshlycutorpolished Goodconductorsofheatandelectricity Generallymalleable,ductile,flexible Tendtogiveupelectronsduringchemicalreactions TheNon-Metalsarelocatedintheupperrightportionofthetable.Propertiesofnonmetalsinclude: • Usuallygasesorbrittlesolidsatroomtemp. • Solidnon-metalsranginginappearancefromdullorlustrousandtranslucentto apaque • Poorconductorsofheatandelectricity • Duringchemicalchangestendtogainelectronsfrommetalstoformanionsor shareelectronswithothernon-metals 1 Theperiodictableisarrangedaccordingtotheatomicnumberoftheelements.This organizationshowsthatthechemicalandphysicalpropertiesrepeatinaregular,periodic pattern. Anelement’speriodnumberisthesameasthenumberofenergylevelsthatitselectrons occupy. Forthemaingroupelements,thenumberofvalencee-‘sisequaltothegroupnumber(1,2)or equaltothegroupnumberminus10(13-18). AtomicRadius(Size) Anatom’ssizeismeasuredbyit’sradius:thedistancefromthenucleustotheapproximate outerboundaryofthecloud-likeregionofitselectrons Asyougodownagroup,thesizeoftheatomincreases.Thevalencee-‘sarefartherandfarther awayfromapositivenucleusandtheinnerelectronsshieldthevalencee-‘sfromthepositive charge. Acrossaperiod,thesizeofanatomdecreases.Eventhoughthenumberofelectronsincreases, theystayinthesameenergylevel.Theincreasingpositivechargeofthenucleuspullsthe electronscloser,reducingtheatom’ssize. Homeworkpg.34#13,15,16,17 IonizationEnergy Anatomthatgainselectronsbecomesnegativelycharged(anion).Anatomthatloseselectrons becomespositivelycharged(cation).Theenergyrequiredtoremoveane-fromanatomis calledionizationenergy(IE). Ionizationenergy_____________________downagroupand_______________acrossaperiod. 2 ElectronAffinity Electronaffinity(EA)isthechangeinenergythatoccurswhenane-isaddedtotheouter energylevelofanatomtoformananion.AhighEAmeansthatenergyisreleasedwhenan atomgainsane-,andthatitislikelytoformananion.AlowEAmeansthatenergyisabsorbed whenanatomgainsane-,andthatitisnotlikelytoformananion. Electronaffinitygenerally______________________downagroupand____________________acrossa period. 3
