chemistry chapters 10 and 6

7/28/2019 chemistry chapters 10 and 6

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VII.NeilBohrplanetarymodeloftheatom 1913.

A. Goals;1.Atommustbestable.2.Explainchemicalperiodicity.3.Includedthequantumidea.4.Explainatomicspectroscopy.

B. Postulatesofthemodel;1. Theelectroncanexistinonlycertaincircularorbits&whileinthese

orbits,theelectrondoesnotloseenergy.

2. Theenergyoftheelectroninanorbitisquantized(discrete).3. Theelectroncanjumpfromoneorbittoanother&insodoingwill

eithergainorloseenergy.

C. AgeneralpictureoftheBohrplanetarymodel;D.Shells,orbits,levelsareSynonymous.

E. Howmanyelectronscaneachorbitholds?2n

2(1)=2

2(2)=8

2(3)=18

2(4)=32


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F. HowdidtheBohrmodelexplainchemicalperiodicity?Chemicalperiodicityrepeatingpatternofpropertiesagainsttheelements.

Toexplainthis;Bohr'smodelpicture;

BohrmodelpictureforelementsZ=1toZ=20

Outershell=valenceelectronsnumberofpoundsofelectrondeterminesthe

mostphysicalandchemicalproperties.

G. HowdidtheBohrmodelstabilizetheatom?Secondpartofpostulatesone.

H. HowdidtheBohrmodelincludethequantaidea?Forhydrogenatom:E =

.

* electronvolt(tinyunitofenergy)


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I. HowdidtheBohrmodelexplainatomicspectroscopy?Atomicspectroscopypostulate2&3;

h=0

Surfacerun2

2

2

2

2

8+10=+2

8(10)


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J. Energyleveldiagram; 0

.850m=E

1.51m=E3.40m=E

13.6m=E

*levelsbegintocometogethercalledcontinuous

*Groundstateforthehydrogenatom

Allelectronsinthelowestpossibleenergylevels

Hydrogenatom

Electrontransition 1 2

=E E =+10.2ev

E

*excitedstate oneormoreelectronsarenotinthelowestpossibleenergylevel.

Electronmustgainthisabsorbedenergytojump12.

Source;

1. Heat.2. Electricity3. Light

*electronabsorbswhatitneedsleasttorest.

*themustonexactmatch.

*energyneededbytheelectron

Ifhf=10.2ev *thentheelectronabsorbsit&jumps12

Areinstantaneous

Ifhf,doesnotequal10.2ev *thentheelectronabsorbsitanditpassesthroughtheatomunabsorbed.


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E =.

= 13.6ev

E.

= 3.40ev

E=.

= 1.51ev

E =.

= .850ev

|

|

|

E .

= 0

K. Whatdoesitmeantohavenegativeenergy?Attractiveforceactingontheelectron

100=50

150=0

200=

250=

L.

movinguptheenergyleveldiagramrequiresenergy


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M.Movingdowntheenergyleveldiagramreleasesenergy 0 0

E= E=

E= E=

E=e E=

E= 21 E=e

E=EE=10.2ev

*electronmustreleasetheamountofenergytojump21

*exactedstate areunstable.

Lastfor ~1ns

*theformofenergyisalwaysaprotonoflight.LightmeaningUV,visible,IR.

(Emissionspectrumbrightline) 4lines.

43 43 42

31 32 42

21 41 21

Allshouldoccur

N.TheBohrmodelworksmathematicallyonlyforhydrogenatoms. Bigsuccesses1. Chemicalperiodicity.2. Anatomicspectrumofhydrogen.

*Bohrcalculateswavelength,werealmostexact.

*Otheratomarenotequal.

Bigfailure Bohrsmodelworksmathematicallyonlyforhydrogen.

Otherminorproblemswereovercomeoverthenextfewyears(19131917).But

themainproblemcouldnotbeovercome.


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O.Fluorescence;absorptionofhighenergylight(UV)followedbytheimmediatereleaseoflowerenergylightblue.

P. Phosphorescence (glowinthedark)absorptionofhighenergylight(UV)followedbydelayedreleaseoflowerenergylightbluish(regionofthe

spectrum).


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Q.Thewavenatureofmatter;1. DeBroglie1924 iflightcansometimesbehaveasaparticle,then

maybemattercansometimesbehaveasawave.Waveparticle

duality

Wavelengthofamatterwave; =

h=planksconstant( 10 )

m=mass

v=velocity

Ordinarysizematterhassuchlargemasscomparedtohydrogenthatits shouldbelargeenoughtodetectandaffectbehavior.

Subatomicsizematter(electrons)hasannouncedalmostassmallashydrogenbondedit shouldbelargeenoughtodetectandaffectbehavior.

2. Davisson,GermerandG.Thomson 1927Experimentallydiscoveredthewavenatureoftheelectrons.

Discoveredthatelectronbeamsshoweddiffraction(waveproperty).

(Basesforelectronmicroscope).

VIII.Themoderntheoryoftheatom quantummodel 1925

Quantumtheoryorquantummechanics; Threeindependentlyworkingscientist;a) Diracquantumalgebra.Mostgeneralusingverydifficultmathematics

(quantumalgebra).Atomcouldnotbepictured.Notwellaccepted.b) Heisenberg matrixmechanics.Difficultmathematics,concernedonlywith

measurablequalities(matrixmechanics).Atomcouldnotbepictured.Not

wellaccepted.

c) 1926ErwinSchroedinger wavemechanics.Creatingmathematicalmodelthatdescribedelectronsaswaves.Treattheelectronasawaveinsidethe


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nucleusofanatom(wavemechanics).Mathematicsofwaveswaswell

understood.Atomcouldbepictured.

Anyatom Setup Schroedingerwaveeqn ormolecule.(S.W.E)

Thistreatmentofatomsledtoabranchofphysicscalledwavemechanicsorquantummechanics.

*Everythinginnatureallowsustoknow

almosttheelectroninthequantumatom

Exactlyonlyforhydrogen

Itcanbesolvedalmosttheexactly

d) Howaretheelectronsorganizedwithinthequantumatom?Bohrmodel vs. Quantummodel

Quantumnumbers.

Bohrmodelelectronexistsinlevels(n=1,2,3.). Forhydrogen

Energy

Radius

Velocity(speed)

Solveit

for


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Quantummodel4q.ns

electronsexistsinlevels(n=1,2,3..).

Levelsbreakdownintosublevels(l=0,n1)Sublevelsbreaksdownintoorbitals( = l0+ l ) Orbitalsbreaksdownintospinorbitals( =+, )

Quantummodel=(q n)

Bohrmodel vs. Quantummodel

Quantumnumbers.

Name Symbol Labelswhat Determineswhat

1. Principal n(1,2,3) Levels Energyofelectron,andmostprobabledistancefromthe

nucleus.

2. Orbital l(0,1,n1) Sublevels (Energy)&shapeoftheelectroncloud.Morethanoneelectron.

3. Magnetic (-l,o+ l) Orbitals Orientation(direction)theelectrocloudpoints.

4. Spin (+, ) Spin orbitals Spinoftheelectron.


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e) Quantumnumberscanbethoughtofastheaddressesoftheelectrons;n=state,l=city, =street, =maleorfemale.

1. Eachlevelconsistsofsublevels.Eachsublevelconsistsoforbitals.

Levels

Sublevels

Orbitals


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2. ThePauliexclusionprinciple;Anatomicorbitalcanholdamaximumoftwoelectrons,whichmusthaveoppositespins.

Thefirstprincipleenergylevelcontainsonetypeoforbital(1s)thatholdsa

maximumoftwoelectrons.

3. Howmanyelectronscaneachsublevelandlevelhold?Quantumnumberasanaddress;n=state,l=city, =street, =female

ormale

maximumelectrons numberoforbitals levels letters

2 1 0 Sharp

4 3 1 Principal

6 5 2 Diffuse

8 7 3 Fundamental

18 9 4 G..(followsthe

alphabet)


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4. Thesublevelscanbeorderedbyenergy.Energysubleveldiagram;

E=0

4p

3d

4s

3p

3s

2p

2s

1s

2 2 6 2 6 2 10 6

1s 2s 2p 3s 3p 4s 3d 4p

5. Notation

6. Orbital regionaroundthenucleuswitha90%probabilityoffindingtheelectron.Withthataddress(n=state,l=city, =street, =maleor

female).

Housingunits


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7. Eachtypeoforbitalhasadifferentshape;orbitalshapeisdeterminedbythe llevel.

a. sorbitals (l=0)allhaveasphericalshape.

b.porbitals (l=1)allhaveadumbbellshapeorfigure8.


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8. Probabilityplaysamajorroleinthequantumtheory; Bohrsmodelcalculationforhydrogengivesexactvalues. Quantummodelcalculationsgiveonlyprobabilities.

Wavefunction theprobabilityvalue

9. Heisenberguncertaintyprinciple;themoreaccurately,thepositionofanelectronismeasured,thelessaccurately

thespeedcanbemeasured,andviceversa. Quantumatomisfuzzy.

Builtintonature cannotbeovercomewithtechnology. Duebecause;atthequantumlevel,observingasystemnecessarilydisturbs

it.

Energyandtimearealsorelatedinthisway.Thismeansoververyveryshorttime(10s)theuncertaintyandenergyissolargethatmatter

(energy)canbecreatedoutofnothingness&disappearbackinto

nothingnessveryveryquickly.

(Virtual particles)

emptyspacequantumfoam.

violationofthelawofconcentrationofmatterenergy.


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2 2 6 2 6 2 10 6

1s 2s 2p 3s 3p 4s 3d 4p

( ) ( ) ( ) ( )

10.Aufbauprinciple sublevelsfillfromlowesttohighestenergy(lefttoright).

Interpretation

Copehogen

probabilities uncertainty

manyworlds

everyquantumchoiceproducesa

newworld

universe.


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11.Valenceelectrons electronsintheoutermost(highest)energylevelofanatom.Example;oxygen,whichhaselectronconfigurationof1s2s

2p.

12.Buildingtheelementsinthequantummodel;=spin=+

,

+ up

down

Pauliexclusionprinciple eachorbitcanholdamaximumoftwoelectrons,andtheseelectronsmusthaveoppositespins.


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Energyorbitaldiagram

E=0

|

|

|

|

___

4p

_____3d

_

4s

___

3p

_

3s

___

2p

_

2s

_

1s

13.Hundsrule whenplacingelectronintothedegeneratedorbital,theyremainunpairedaslongaspossible.

14.Isoelectronic havingthesameelectronconfiguration.15.Octethavingeightvalanceelectrons.


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16.TheperiodicLawthereisarepeatingpatternofphysicalandchemicalproperties.periodiclaw&chemicalperiodicity.

IX.Modernperiodictable basedonthedivisionscreatedbyMendeleev&

Meger.

Mendeleev fatheroftheperiodictable

Periodshorizontalrows. Groupsverticalcolumns

Mainsystem:

Americansystem:AA

Europeansystem:AA

Unifiedsystem:1 18

A.Certaingroupshavespecialnames;A

group

elements maingrouporrepresentativeelements

B groupelementstransitionelements.


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4) Havehighm.p.&b.p.5) Allbutonearesolidatroomtemperature(Mercury).6) Goodconductorsofheatandelectricity.7) Tendtoloseelectronsduringchemicalchanges

b)NONMETALS;1) Nonlustrous2) Brittle.3) Convertibleassolids.4) Havelowerm.p.&b.p.5) Allbutonearegasesorsolid.6) Poorconductorsofheatandelectricity.7) Tendtogainelectronsduringchemicalchanges.

c) METALLOIDS;1) Havesomemetalproperties.2) Havesomenonmetalproperties.3) Havesomenewproperties.

d) Whichismoremetallic?Goingdown agroup:metallicnatureincreases.

Goingprocessesaperiod:metallicnaturedecreases.

Na vs. K Mg vs. Al

K vs. Mg Na ?vs.? Ca


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3. Atomicsize:Atomstonothaveasharpboundary(fuzzy).a) TheQuantumatomisfuzzy

Covalentradius

ductusbetweenthenuclei.

b) Goingdownagroup:atomicsizeincreasesbecauseoftheaddedlevel(Agroup)

c) goingacrossaPeriod:atomicsizeslightlydecreases.d) Anytwoelementscanbecomparedastoatomicsize;

Na vs. K Mg vs. Al

K vs. Mg Na ?vs.? Ca

4. Ionizationenergy(I.E.) energyrequiredtoremovetheoutermostelectronfromgaseousatomorion.

a) 1st ionizationenergy=energyrequiredtoremovethefirstoutermostelectronfromgaseousatom.


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b)Goingdownagroup:1stionizationenergydecreasessincetheelectronbeingremovedisheldlesstightlyastheatomgetsbigger.

c) Acrossaperiod:1stionizationenergyincreasesslightly.(Itdoesirregularly).

d) Higherionizationenergybeyondthe1ste) Thehighertheionizationlevelthelargerenergiesrequired.

1st

I.E.


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Element Electron

configuration

OrbitalDiagram #ofvalence

electrons

Dot

formula

1. H 1e 1s

1s

1 H

2. He 2e 1s

1s

2 He

3. Li 3e 1s 2s 1 Li

4. Be 4e 1s 2s 2 Be

5. B 5e 1s2s2p 3 B

6. C 6e 1s2s2p 4 C

7. N 7e 1s2s2p 5 N

chemistry chapters 10 and 6

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