114
Recall
Recall
TheQuantumMechanicalModel
QuantumNumbers• Fournumbers,calledquantumnumbers,describethecharacteristicsofelectronsandtheirorbitals
QuantumNumbers
QuantumNumbers
TheCaseofHydrogen
Orbitals• Forhydrogen,allorbitalswiththesamevalueofnhavethesameenergy
Orbitals• EnergystatesofaHydrogenAtom
– Inthegroundstate,electronresidesinthe1sorbital– Anexcitedstatecanbeproducedbytransferringtheelectrontoahigher-energyorbital
SampleQuestion• Aground-stateelectroninthehydrogenatomisgivenjustenoughenergytogetton=2– Whichorbitalwilltheelectronoccupy?a. 2sorbitalb. 2pxorbitalc. 2pyorbitald. 2pzorbitale. Eachoftheaboveorbitalsisequallylikely
ElectronSpin&thePauliPrinciple
ElectronSpin&thePauliPrinciple• WolfgangPauli
– StudiedunderMaxBornandNielsBohr
– Formulatedhisexclusionprinciplein1925forelectrons(Wolfgangwas25)
– Helpedestablishthefoundationsofquantumtheory
– Alsothefirsttorecognizetheexistenceoftheneutrino
– WonNobelPrizeinPhysicsin1945
ElectronSpin&thePauliPrinciple• Electronspinquantumnumber(ms)
– Canbe+1/2or-1/2– Indicatesthatthee-canspininoneoftwooppositedirections
• PauliExclusionPrinciple– Inagivenatom,notwoe-scanhavethesamesetoffourquantumnumbers
– Anorbitalcanholdonlytwoe-s,andtheymusthaveoppositespins
Figure7.20-TheSpinningElectron
SampleQuestion• Whichofthefollowingcombinationsofquantumnumbersisnotallowed?nℓ mℓ msa. 1 1 0 ½b. 3 0 0 –½c. 2 1 –1 ½d. 4 3 –2 –½e. 4 2 0 ½
PolyelectronicAtoms
PolyelectronicAtoms• Polyelectronicatoms
• Atomswithmorethanoneelectron,suchasHe,N,etc.
• Alsocalledmulti-electronatoms• Hydrogenistheonlyatomthathasonee-intheorbitalsundergroundstate
PolyelectronicAtoms• Polyelectronicatoms
PolyelectronicAtoms• Polyelectronicatoms
• Therearemanyenergies/forcesatplaywhentherearemultipleelectronspresent:
– Movingelectronshavekineticenergy– Attractiveforcesbetweenthenucleusandelectrons
– Repulsiveforcesbetweenelectrons
Youshouldbeabletodiscussallofthese
PolyelectronicAtoms• Polyelectronicatoms
• Howdotheadditionale-sbehaveandaffecttheatom?
• Additionale-smeansgreaterrepulsionintheatom,andelectronstendtobeasfarawayfromeachotheraspossible
PolyelectronicAtomsEffectofprotons:
• However,moreprotonsmeansagreaterattractiveforcefore-s,sotheywillbepulledclosertowardthenucleus
PolyelectronicAtomsElectronshielding
• Whentherearemultipleenergylevels,moree-salsocreateashieldingeffect,wheree-sclosertothenucleusblockoutervalencee-sfromgettingclosetothenucleus
• Itiseasiertoremoveouter/valencee-sduetothisshieldingeffect
PolyelectronicAtoms• Atomsotherthanhydrogenhavevariationsinenergyfororbitalshavingthesameprincipalquantumnumber
• Electronsfillorbitalsofthesamenvalueinpreferentialorder
Ens<Enp<End<Enf
PolyelectronicAtoms• Polyelectronicatoms
• Electrondensityprofilesshowthatselectronspenetratetothenucleusmorethanotherorbitaltypes
– Inotherwords,anelectronina2sorbitalismorestronglyattractedtothenucleusthananelectronina2porbital
• Closerproximitytothenucleus=lowerenergy– The2sorbitalislowerinenergythanthe2porbital
SampleQuestion• Whenanelectronisplacedinaparticularquantumlevel,theyprefertheorbitalsinwhatorder?a. p,f,d,sb. s,p,f,dc. s,p,d,fd. f,d,p,s
TheHistoryofthePeriodicTable
TheHistoryofthePeriodicTable• ThePeriodicTable
TheHistoryofthePeriodicTable• ThePeriodicTable
– Originallyconstructedtorepresentthepatternsobservedinthechemicalpropertiesofelements
TheHistoryofthePeriodicTable• ThePeriodicTable
– JohannDobereineràtriadmodel– Groupsofthreeelementswithsimilarproperties
TheHistoryofthePeriodicTable• ThePeriodicTable
– JohnNewlands– Suggestedthatelementsshouldbearrangedinoctaves
TheHistoryofthePeriodicTable• TheModernPeriodicTable
– ConceivedbyJuliusLotharMeyerandDmitriIvanovichMendeleev
TheHistoryofthePeriodicTable• TheModernPeriodicTable
– Mendeleevemphasizedtheusefulnessoftheperiodictableinpredictingtheexistenceandpropertiesofstillunknownelements
– Usedtotabletocorrectseveralvaluesofatomicmasses
52
ElectronConfigurations
ArrangementofElectronsinAtoms• Levels(n)
• Sublevels(l )
• Orbitals(ml )
ElectronConfigurations:AReview
Energy Levels
n=1
n=2
n=3n=4
ArrangementofElectronsinAtoms• Electronconfiguration=arrangementofe-sinatoms
ArrangementofElectronsinAtoms• e-sassumeanarrangementthatgivestheatomthelowestenergypossible(morestable)
ArrangementofElectronsinAtoms• Whatdoesthislooklike?
Electron Configurations
2p4EnergyLevel
Sublevel
Numberofelectronsinthesublevel
1s22s22p63s23p64s23d104p65s24d105p66s24f14…etc.
ArrangementofElectronsinAtoms• Whatdoesthislooklike?
AufbauPrinciple• “Asprotonsareaddedonebyonetothenucleustobuildupelements,electronsaresimilarlyaddedtothesehydrogen-likeorbitals”
AufbauPrinciple• AufbauPrinciple=e-soccupythelowestEorbitalavailable.
• Usethediagonalrule
DiagonalRules
s3p3d
s2p
s4p4d4f
s5p5d5f5g?
s6p6d6f6g?6h?
s7p7d7f7g?7h?7i?
1
2
3
4
5
6
7
PauliPrinciple• PauliExclusionPrinciple=Nomorethantwoe-scanoccupyasingleorbital
• Wenotethisusingarrowsinoppositedirections
Hund’sRule• “ThelowestenergyconfigurationforanatomistheonehavingthemaximumnumberofunpairedelectronsallowedbythePauliprincipleinaparticularsetofdegenerateorbitals”
Hund’sRule• Hund’sRule=Fillinsinglee-sinseparateequal-energyorbitalsbeforedoublingup
Rules1)Determinethe#ofe-sbylookingupZ(atomicnumber)• Assumetheatomisneutralunlessstatedotherwise.Draworbitalsfirsttohelpyou.
• Ex/Nitrogen
Rules2)StartfillingorbitalsinorderofincreasingEaccordingtotheAufbauPrinciple.• Asingleorbitalcanholdamaxof2e-s
OrbitalType NumberofOrbitals
s 1p 3d 5f 7
Rules3)Hund’sRuleApplies:Drawallorbitalsforeachtype,andfillinONEe-ineachorbitalbeforedoublingup.
Rules4)PauliExclusionapplies:Twoe-sinthesameorbitalmusthaveoppositespins
Rules5)Doublechecknumbers.• Makesuretotal#ofe-sinyourconfigurationmatchestheatomicnumber(ifyouratomisneutral)
Orbitals and the Periodic Table
• Orbitalsgroupedins,p,d,andforbitals
sorbitals
porbitalsdorbitals
forbitals
Examples
Writetheorbitalnotationande-configurationfor…• Hydrogen
Writetheorbitalnotationande-configurationfor…• Fluorine
Writetheorbitalnotationande-configurationfor…• Magnesium
Writetheorbitalnotationande-configurationfor…• Neon
Writetheorbitalnotationande-configurationfor…• Arsenic
Orbitals and the Periodic Table
• Orbitalsgroupedins,p,d,andforbitals
sorbitals
porbitalsdorbitals
forbitals
ShorthandNotation
ShorthandNotation
• Wecanabbreviateourlonge-configurationsbyusingournoblegases
• ThisisbecauseourNobleGaseshavecompletefullporbitals– Note:onlydothiswhenaskedto
ShorthandNotation1. Findtheclosestnoblegastoyouratomwitha
smallerZ2. Add/fillorbitalsfromwheretheNobleGasleft
off
ShorthandNotation• Ex/Na
ShorthandNotation• Try:• Cl
• Ca
SampleQuestion• Howmanyofthefollowingelectronconfigurationsforthespeciesintheirgroundstatearecorrect?– Ca:1s22s22p63s23p64s2– Mg:1s22s22p63s1– V:[Ar]3s23d3– As:[Ar]4s23d104p3– P:1s22s22p63p5
a. 1b. 2c. 3d. 4e. 5
SampleQuestion• Inwhichofthefollowinggroupsdoalltheelementshavethesamenumberofvalenceelectrons?a) P,S,Clb) Ag,Cd,Arc) Na,Ca,Bad) P,As,See) Noneofthese
SampleQuestion• ElementXhasaground-statevalenceelectronconfigurationofns2np5– WhatisthemostlikelyformulaforthecompoundcomposedofelementXandnitrogen?
a. NXb. NX7c. NX2d. NX3e. NX5
SampleQuestion• Ofthefollowingelements,whichhasoccupieddorbitalsinitsground-stateneutralatoms?a. Bab. Cac. Sid. Pe. Cl
PeriodicTableReview
PeriodicTrends
PeriodicTrendsinAtomicProperties• IonizationEnergy• ElectronAffinity• AtomicRadius
• Itisnotsufficienttoknowthetrends.Youmustbeabletoexplainthetrends.
IonizationEnergy
IonizationEnergy• IE=Energyrequiredtoremoveane-fromagaseousatomorion
X(g)àX+(g)+e-• Ionizationenergyincreasesforsuccessivee-s
– Firstionizationenergy(I1):Energyrequiredtoremovethehighest-energye-ofanatom
– ThevalueofI1issmallerthanthatofthesecondionizationenergyI2
IonizationEnergy• Aswegoacrossaperiodfromlefttoright,I1increases
• Why?• e-sinthesamequantumlevel(n)donotshieldaseffectivelyase-sininnerlevels
• Additionalprotonscausee-sinthesameprincipalquantumlevel(n)tobemorestronglyboundasyougoacrossaperiod
IonizationEnergy• Aswegodownagroup,I1decreases• Why?• e-sbeingremovedarefartherfromthenucleus
• Asnincreases,thesizeoftheorbitalincreasesàremovalofe-sbecomeseasier
IonizationEnergy
Figure7.32-TrendsinIonizationEnergies(kJ/mol)fortheRepresentativeElements
IonizationEnergy• Exceptions
– Half-filledandfilledsublevelshaveirregularitiesduetoextrarepulsionofelectronspairedinorbitals
– Thismakesthemeasiertoremove
SampleQuestion• Thefirstionizationenergyforphosphorusis1060kJ/mol,andthatforsulfuris1005kJ/mol– Why?– Solution:
• PhosphorusandsulfurareneighboringelementsinPeriod3oftheperiodictableandhavethefollowingvalenceelectronconfigurations:– Phosphorusis3s23p3– Sulfuris3s23p4
SampleQuestion• PhosphorusandsulfurareneighboringelementsinPeriod3oftheperiodictableandhavethefollowingvalenceelectronconfigurations:– Phosphorusis3s23p3– Sulfuris3s23p4
• Ordinarily,thefirstionizationenergyincreasesaswegoacrossaperiod,sowemightexpectsulfurtohaveagreaterionizationenergythanphosphorus– However,inthiscasethefourthpelectroninsulfurmustbeplacedinanalreadyoccupiedorbital
• Theelectron–electronrepulsionsthatresultcausethiselectrontobemoreeasilyremovedthanmightbeexpected
ElectronAffinity
ElectronAffinity• ElectronAffinity=Energychangeassociatedwiththeadditionofane-
X(g)+e-àX-(g)• Inotherwords,electronaffinityisameasureofhowlikelyanatomistogainanelectron
• Afterthefirste-isgained,anatomwillreleaseenergy.
• Themoreenergythatisreleased,themorenegativethevaluewillbe.Thisindicatesgreaterfavorabilityforgaininganelectron.
ElectronAffinity• ElectronAffinity=Energychangeassociatedwiththeadditionofane-
X(g)+e-àX-(g)• Aswegoacrossaperiodfromlefttoright,e-affinitiesbecomemorenegative
• Thisisbecauseitismorefavorabletogainanelectronaswegoacrosstheperiodictable
ElectronAffinity
ElectronAffinity• ElectronAffinity=Energychangeassociatedwiththeadditionofane-
X(g)+e-àX-(g)• Affinitytendstodecreaseasyougodownagroup– Electronsarebeingaddedatincreasingdistancesfromthenucleus
– Aselectronsgetfartherfromthenucleus,therearelessnuclearattractiveforcesatplay.
– However,thesechangesarerelativelysmallcompredtothechangesacrossaperiod
ElectronAffinity
ElectronAffinity
ElectronAffinity• Exceptions
– Theremaybesomeirregularitiesduetorepulsiveforcesintherelativelyporbitals
AtomicRadii
AtomicRadii• Obtainedbymeasuringthedistancebetweenatomsinachemicalcompound– Covalentatomicradii–Determinedfromthedistancesbetweenatomsincovalentbonds
– Metallicradii–Obtainedfromhalfthedistancebetweenmetalatomsinsolidmetalcrystals
AtomicRadii• Atomicradiusdecreasesgoingacrossaperiodfromlefttoright– Increasingeffectivenuclearchargewhilegoingfromlefttoright
– Valencee-sareclosertothenucleus,whichdecreasesthesizeoftheatom
AtomicRadii• Atomicradiusincreasesdownagroup
– Causedbytheincreaseinorbitalsizesinsuccessiveprincipalquantumlevels
SampleQuestion• Predictthetrendinradiusforthefollowingions:
– Be2+– Mg2+
– Ca2+– Sr2+
Solution• AlltheseionsareformedbyremovingtwoelectronsfromanatomofaGroup2Aelement– Ingoingfromberylliumtostrontium,wearegoingdownthegroup,sothesizesincrease:
Be2+<Mg2+<Ca2+<Sr2+
Smallestradius
Largestradius
SampleQuestion• Considerthefollowingorders:
I. Al<Si<P<ClII. Be<Mg<Ca<SrIII. I<Br<Cl<FIV. Na+<Mg2+<Al3+<Si4+
– Whichofthesegive(s)acorrecttrendinsize?a. Ib. IIc. IIId. IVe. Atleasttwooftheabovegiveacorrecttrendinsize
SampleQuestion• Considerthefollowingorders:
– Al<Si<P<Cl– Be<Mg<Ca<Sr– I<Br<Cl<F– Na+<Mg2+<Al3+<Si4+
Whichofthesegive(s)acorrecttrendinionizationenergy?
a. IIIb. I,IIc. I,IVd. I,III,andIV
SampleQuestion• Firstionizationenergyofmagnesiumisapproximately700kJ/mol– Whatisagoodestimateforthesecondionizationenergyofmagnesium?
a. 700kJ/molb. 1400kJ/molc. 70,000kJ/mold. −700kJ/mole. −1400kJ/mol
SampleQuestion• Whichofthefollowingstatementsconcerningsecondionization
energyvaluesistrue?a. SecondionizationenergyofAlishigherthanthatofMgsince
Mgwantstolosethesecondelectron,soitiseasiertotakethesecondelectronaway
b. SecondionizationenergyofAlishigherthanthatofMgbecausetheelectronsaretakenfromthesameenergylevel,buttheAlatomhasonemoreproton
c. SecondionizationenergyofAlislowerthanthatofMgbecauseMgwantstolosethesecondelectron,sotheenergychangeisgreater
d. SecondionizationenergyofAlislowerthanthatofMgbecausethesecondelectrontakenfromAlisinaporbital,soitiseasiertoremove
e. SecondionizationenergiesareequalforAlandMg
SampleQuestion• FortheatomsLi,N,F,andNa,whichofthefollowingisthecorrectorderfromsmallesttolargestatomicradius?a. Na,F,N,Lib. Na,Li,N,Fc. Li,N,F,Nad. N,F,Na,Lie. F,N,Li,Na
SampleQuestion• WhichofthefollowingcorrectlyrankstheionizationenergiesofO,F,Na,S,andCsfromsmallesttolargest?a. Cs,Na,S,O,Fb. Cs,S,Na,O,Fc. F,O,Na,S,Csd. F,O,S,Na,Cse. Na,S,Cs,F,O
Pair-Share-Respond 1. Explainwhyionizationenergyincreases
acrossaperiodanddecreasesdownagroup2. Explaintoyourneighborwhatelectron
affinitymeans3. Explainwhyelectroninfinityincreasesacross
aperiodanddecreasesdownagroup.4. Explainwhyatomicradiidecreaseacrossa
period,andincreasedownagroup
NotesonGroupProperties
PropertiesofaGroup• Numberandtypeofvse-sprimarilydetermineanatom’schemistry
• e-configurationsofrepresentativeelementscanbedeterminedfromtheorganizationoftheperiodictable
• Certaingroupsintheperiodictablehavespecialnames
PropertiesofaGroup• Elementsintheperiodictablearedividedintometalsandnonmetals– Metalshavelowionizationenergies– Nonmetalshavelargeionizationenergiesandnegativee-affinities
– Metalloids(semimetals):Elementsthatexhibitbothmetallicandnonmetallicproperties
Figure7.38-SpecialNamesforGroupsinthePeriodicTable
Figure7.38-SpecialNamesforGroupsinthePeriodicTable(continued)
AlkaliMetals• Mostchemicallyreactivemetals• Reactwithnonmetalstoformionicsolids• Hydrogen
– Exhibitsnonmetalliccharacterduetoitssmallsize
AlkaliMetals• Trends:• Firstionizationenergy
– Decreasesdownthegroup• Atomicradius
– Increasesdownthegroup• Densityincreases• Meltingandboilingpointssmoothlydecrease
AlkaliMetals• ChemicalProperties:• Group1Aelementsarehighlyreactive• Relativereducingabilitiesarepredictedfromthefirstionizationenergies– ReducingabilitiesinaqueoussolutionareaffectedbythehydrationofM+ionsbypolarwatermolecules
• Energychangeforareactionandtherateatwhichitoccursarenotnecessarilyrelated
