Lecture 33 CH101 A1 (MWF 9 am) Fall 2016
Lecture 33 CH101 A1 (MWF 9 am) Fall 2016
2/6/2017 1:13 PM
Copyright © 2016 Dan Dill [email protected]
Lecture 33 CH101 A1 (MWF 9 am)
TP WhatistheoxidationnumberofthemiddleC inCH3CH2C O OH?
11%
11%
11%
11%
11%
11%
11%
11%
11%
Friday, December 2, 2016
1.
4
2.
3
3.
2
4.
1
5. 0
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1
7.
2
8.
3
9.
4
•
•
•
•
Nextlecture: Buildingelectronconfigurations;Successiveionization
energies;Beginch 10:Modellingbondinginmolecules.Bondingin
diatomicmoleculeshttp://goo.gl/1h0S9C
0 of 0
Lecture 33 CH101 A1 (MWF 9 am) Fall 2016
Review:Lewisstructures,formalchargeandoxidationnumber
Review:Electronclouds
Morethanoneelectron:Orbital yikes! approximation
Electricalshieldingofoneelectronbyothershttp://goo.gl/hMNPLA
1
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Lecture 33 CH101 A1 (MWF 9 am) Fall 2016
Copyright © 2016 Dan Dill [email protected]
Pictorial recipe for formal charge
Pictorial recipe for oxidation number
Formalcharge:Partitionsharedelectronsequally.
Oxidationnumber:Moreelectronegativeatomgetsallsharedelectrons.
CH3C O OH
CH3C O OH
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1
Lecture 33 CH101 A1 (MWF 9 am) Fall 2016
Lecture 33 CH101 A1 (MWF 9 am) Fall 2016
2/6/2017 1:13 PM
Copyright © 2016 Dan Dill [email protected]
TP WhatistheoxidationnumberofthemiddleC inCH3CH2C O OH?
11%
11%
11%
11%
11%
11%
11%
11%
11%
Lecture 33 CH101 A1 (MWF 9 am) Fall 2016
Copyright © 2016 Dan Dill [email protected]
Pictorial recipe for oxidation number
1.
4
2.
3
3.
2
4.
1
5. 0
6.
1
7.
2
8.
3
9.
4
Oxidationnumber:Moreelectronegativeatomgetsallsharedelectrons.
CH3CH2C O OH
0 of 0
Lecture 33 CH101 A1 (MWF 9 am) Fall 2016
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Lecture 33 CH101 A1 (MWF 9 am) Fall 2016
Copyright © 2016 Dan Dill [email protected]
Review: Electron clouds
Review:Electronclouds
Sketchthedensityofthe1selectroncloudversusdistancefromthenucleus.
10
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Lecture 33 CH101 A1 (MWF 9 am) Fall 2016
Lecture 33 CH101 A1 (MWF 9 am) Fall 2016
2/6/2017 1:13 PM
Copyright © 2016 Dan Dill [email protected]
1s electron cloud
Lecture 33 CH101 A1 (MWF 9 am) Fall 2016
1s electron cloud
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Lecture 33 CH101 A1 (MWF 9 am) Fall 2016
Copyright © 2016 Dan Dill [email protected]
Copyright © 2016 Dan Dill [email protected]
1s electron cloud
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Lecture 33 CH101 A1 (MWF 9 am) Fall 2016
Copyright © 2016 Dan Dill [email protected]
Review: Electron clouds
Sketchthedensityofthe2selectroncloudversusdistancefromthenucleus.
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3
Lecture 33 CH101 A1 (MWF 9 am) Fall 2016
Lecture 33 CH101 A1 (MWF 9 am) Fall 2016
2/6/2017 1:13 PM
Copyright © 2016 Dan Dill [email protected]
2s electron cloud
Lecture 33 CH101 A1 (MWF 9 am) Fall 2016
Copyright © 2016 Dan Dill [email protected]
Review: Electron clouds
Sketchthedensityofthe2pelectroncloudversusdistancefromthenucleus.
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Lecture 33 CH101 A1 (MWF 9 am) Fall 2016
Copyright © 2016 Dan Dill [email protected]
2p electron cloud
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Lecture 33 CH101 A1 (MWF 9 am) Fall 2016
Copyright © 2016 Dan Dill [email protected]
Orbital (!) approximation
Assignelectronstoone‐electron waves;forhistoricalreasonsthesearecalled
orbitals yikes! .
Thisassignmentwouldbeexact ifelectronsdidnotrepeloneanother.
Becauseelectroncloudsarediffuse,repulsionisrelativelysmallandsothe
orbitalapproximationisagoodstartingpoint.
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Lecture 33 CH101 A1 (MWF 9 am) Fall 2016
Lecture 33 CH101 A1 (MWF 9 am) Fall 2016
2/6/2017 1:13 PM
Copyright © 2016 Dan Dill [email protected]
Lecture 33 CH101 A1 (MWF 9 am) Fall 2016
Copyright © 2016 Dan Dill [email protected]
Adjusting orbital approximation
Orbital size and shielding
Orbitalsizeandshielding
Whenthereismorethanoneelectron,theone‐electron‐atomenergyformula
canbegeneralizedto
Pauliprinciple
Orbitalenergy 13.6eVZeff2/n2
whereZeff istheeffectivenuclearcharge.
Zeff issmallerthanthenumberofprotons,totakeintoaccountshielding
cancellation ofsomeoftheprotonschargebyotherelectronsthatarecloser
tothenucleus.
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Lecture 33 CH101 A1 (MWF 9 am) Fall 2016
Copyright © 2016 Dan Dill [email protected]
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Lecture 33 CH101 A1 (MWF 9 am) Fall 2016
Orbital size and shielding
Orbital size and shielding
Theapproximatesizeoftheorbitalis
Theionizationenergyoftheorbitalis
Orbitalsize
50pmn2/Zeff
IEorbital E∞ 13.6eVZeff2/n2 0 13.6eVZeff2/n2
Thismeans…
13.6eVZeff2/n2
themoreloops,thebigger theorbitalcloud,and…
thelargerZeff,thesmaller theorbitalcloud.
ThesmallerZeff andthelargern,themoreeasilytheelectroncanbeionized.
24
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Copyright © 2016 Dan Dill [email protected]
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Lecture 33 CH101 A1 (MWF 9 am) Fall 2016
2/6/2017 1:13 PM
Lecture 33 CH101 A1 (MWF 9 am) Fall 2016
Copyright © 2016 Dan Dill [email protected]
Lecture 33 CH101 A1 (MWF 9 am) Fall 2016
Copyright © 2016 Dan Dill [email protected]
Electrical shielding of one electron by others
http://goo.gl/hMNPLA
Demonstration:
Electricalshielding
26
Lecture 33 CH101 A1 (MWF 9 am) Fall 2016
The goal: Why
Copyright © 2016 Dan Dill [email protected]
1s22s
and not
1s22p
27
Lecture 33 CH101 A1 (MWF 9 am) Fall 2016
1s2
Copyright © 2016 Dan Dill [email protected]
portion of Li electron cloud
TheLiatomelectronconfiguration1s22sismorestablethan1s22p.
Thereasonis,the2selectronfeelsagreaternuclearcharge,Zeff,thandoesthe
2pelectron.
Thefollowingillustrations http://goo.gl/hMNPLA showqualitativelywhy
thisisso.
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Lecture 33 CH101 A1 (MWF 9 am) Fall 2016
2/6/2017 1:13 PM
Lecture 33 CH101 A1 (MWF 9 am) Fall 2016
Copyright © 2016 Dan Dill [email protected]
2s portion of Li 1s22s electron cloud
Lecture 33 CH101 A1 (MWF 9 am) Fall 2016
Copyright © 2016 Dan Dill [email protected]
2s outer loop of Li 1s22s electron cloud
30
Lecture 33 CH101 A1 (MWF 9 am) Fall 2016
2s outer loop is shielded by
Copyright © 2016 Dan Dill [email protected]
1s2
Lecture 33 CH101 A1 (MWF 9 am) Fall 2016
Copyright © 2016 Dan Dill [email protected]
For ~90% of 2s, Zeff,outer ≈ 0.90 x (3 – 2) = 0.9
cloud
32
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Lecture 33 CH101 A1 (MWF 9 am) Fall 2016
Lecture 33 CH101 A1 (MWF 9 am) Fall 2016
2/6/2017 1:13 PM
Copyright © 2016 Dan Dill [email protected]
2s inner loop of Li 1s22s electron cloud
Lecture 33 CH101 A1 (MWF 9 am) Fall 2016
Copyright © 2016 Dan Dill [email protected]
2s inner loop is not shielded by 1s2 cloud
34
Lecture 33 CH101 A1 (MWF 9 am) Fall 2016
Copyright © 2016 Dan Dill [email protected]
For ~10% of 2s, Zeff,inner ≈ 0.10 x 3 = 0.3
Lecture 33 CH101 A1 (MWF 9 am) Fall 2016
Copyright © 2016 Dan Dill [email protected]
Zeff,2s = Zeff,outer + Zeff,inner = 0.9 + 0.3 = 1.2
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Lecture 33 CH101 A1 (MWF 9 am) Fall 2016
Lecture 33 CH101 A1 (MWF 9 am) Fall 2016
2/6/2017 1:13 PM
Copyright © 2016 Dan Dill [email protected]
Li 1s22s valence electron energy
Lecture 33 CH101 A1 (MWF 9 am) Fall 2016
Copyright © 2016 Dan Dill [email protected]
2p portion of Li 1s22p electron cloud
E2s 13.6eVZeff,2s2/4
13.6eVx1.22/4 −4.90eV
38
Lecture 33 CH101 A1 (MWF 9 am) Fall 2016
2p is shielded by
Copyright © 2016 Dan Dill [email protected]
1s2
cloud
Lecture 33 CH101 A1 (MWF 9 am) Fall 2016
Copyright © 2016 Dan Dill [email protected]
For ~100% of 2p, Zeff,2p ≈ 1 x (3 – 2) = 1
40
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Lecture 33 CH101 A1 (MWF 9 am) Fall 2016
Lecture 33 CH101 A1 (MWF 9 am) Fall 2016
2/6/2017 1:13 PM
Copyright © 2016 Dan Dill [email protected]
Lecture 33 CH101 A1 (MWF 9 am) Fall 2016
Copyright © 2016 Dan Dill [email protected]
Li 1s22p valence electron energy
Li 1s22s more stable than Li 1s22p
E2p 13.6eVZeff,2p2/4
E2s 13.6eVZeff,2s2/4
13.6eVx12/4 3.40eV
13.6eVx1.22/4 −4.90eV
E2p 13.6eVZeff,2p2/4
13.6eVx12/4 3.40eV
Thereasonis,the2selectronfeelsagreaternuclearcharge,Zeff,
thandoesthe2pelectron.
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Lecture 30 CH101 A2 (MWF 11 am) Fall 2015
Copyright © 2015 Dan Dill [email protected]
Building electron configurations
43
Lecture 30 CH101 A2 (MWF 11 am) Fall 2015
IE1 = 13.6 eV
Copyright © 2015 Dan Dill [email protected]
Zeff2/n2
MakeasketchofIEversusatom,forHthroughNa.
1
Thegoal:Understandthepatternofstabilityacrosstheperiodictable.
6
5
3
4
2
46
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Lecture 33 CH101 A1 (MWF 9 am) Fall 2016
Lecture 30 CH101 A2 (MWF 11 am) Fall 2015
2/6/2017 1:13 PM
Copyright © 2015 Dan Dill [email protected]
Lecture 30 CH101 A2 (MWF 11 am) Fall 2015
Copyright © 2015 Dan Dill [email protected]
Li 1s3?
Energy order of relative spins (Pauli)
Notpossible,sinceatleasttwoelectronswouldhavethesamespininthesame
orbital.
Keypoint:“spin” magneticmoment,eitherupordown
↑↑never;↑↓ worst ↑…↓ ↑…↑ best
Suchanelectronwavevanisheseverywhereandsotherecanbenoatomwith
thisconfiguration.
53
Lecture 30 CH101 A2 (MWF 11 am) Fall 2015
Li
1s22s
or
Copyright © 2015 Dan Dill [email protected]
1s22p?
54
Lecture 30 CH101 A2 (MWF 11 am) Fall 2015
Be
2s2
Copyright © 2015 Dan Dill [email protected]
or 2s2p?
The2sinnerloopescapestheshieldingofthe1s2 partoftheelectroncloud.
2s2 areinsameorbital andsomusthavegreaterelectron‐electronrepulsion
The2phasnoinnerloopandsowouldbemoreshielded bythe1s2 partofthe
electroncloud.
But,the2sinnerloopsresultingreaternuclearattractionthanthe2p.
Hence,the2selectronexperiencesslightlygreaternuclearcharge Zeff andso
itismoretightlyheld thanthe2pelectronwouldbe.
Nuclearattractiontrumpselectronrepulsion,andso2s2 ismorestable.
So,1s22sismorestablethan1s22p
55
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Lecture 33 CH101 A1 (MWF 9 am) Fall 2016
Lecture 30 CH101 A2 (MWF 11 am) Fall 2015
2/6/2017 1:13 PM
Copyright © 2015 Dan Dill [email protected]
Lecture 30 CH101 A2 (MWF 11 am) Fall 2015
Copyright © 2015 Dan Dill [email protected]
B 2s3 or 2s22px or 2s22py or 2s22pz?
C 2px2 or 2px2py?
2s3 isnotpossibleforthesamereasonas1s3 isnot.
2px2 areinsameorbital andsomusthavegreaterelectron‐electronrepulsion
Either2s22px or2s22py or2s22pz arepossibleandequivalent.
Whataboutelectronsindifferent2porbitals?
57
Lecture 30 CH101 A2 (MWF 11 am) Fall 2015
Copyright © 2015 Dan Dill [email protected]
58
Lecture 30 CH101 A2 (MWF 11 am) Fall 2015
Copyright © 2015 Dan Dill [email protected]
Energy order of relative spins (Pauli)
C 2px or 2px2py?
Keypoint:“spin” magneticmoment,eitherupordown
2px2 areinsameorbital andsomusthavegreaterelectron‐electronrepulsion
↑↑never;↑↓ worst ↑…↓ ↑…↑ best
Whataboutelectronsindifferent2porbitals?
↑↓ worst :Electronsinsamespatialregion orbital andsorepel oneanother
themost
2px2py canhavespinsparallelandsodecreasedrepulsion Fermihole .
2
↑…↓:Electronsclump together Fermiclump indifferentspatialregions
orbitals andsorepelsomewhatless
Bothconfigurationshavethesamenuclearattraction Zeff andnoinnerloops .
Hence2px2py or2px2pz or2py2pz morestable.
↑…↑ best :Electrons“avoid”oneanother Fermihole andareindifferent
spatialregions orbitals andsorepeloneanothertheleast
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Lecture 33 CH101 A1 (MWF 9 am) Fall 2016
Lecture 30 CH101 A2 (MWF 11 am) Fall 2015
2/6/2017 1:13 PM
Copyright © 2015 Dan Dill [email protected]
Lecture 30 CH101 A2 (MWF 11 am) Fall 2015
Copyright © 2015 Dan Dill [email protected]
N 2px22py or 2px2py2pz?
O 2px2py22pz or 2px2py2pz3s?
In2px22py the2px isinsameorbital andsomusthavegreaterelectron‐electron
repulsion
2px2py22pz hasincreasedelectronrepulsion Fermiclump .
In2px2py2pz allspinsareparallelandsothereareonlyFermiholesandso
reducedrepulsion.
Hence2px2py2pz ismorestable.
2px2py2pz3shasdecreasedelectronrepulsion Fermihole .
2px2py22pz hasgreaternuclearattractionsincethen 2orbitalsaremore
boundthann 3orbitals.
Nuclearattractiontrumpselectronrepulsion,andso2px2py22pz ismorestable.
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Lecture 30 CH101 A2 (MWF 11 am) Fall 2015
Copyright © 2015 Dan Dill [email protected]
TP ThedecreaseinIE1 fromBetoBprimarilyisdueto…
20%
20%
20%
20%
20%
1.
2.
3.
4.
5.
Copyright © 2016 Dan Dill [email protected]
Lecture 30 CH101 A2 (MWF 11 am) Fall 2015
Copyright © 2015 Dan Dill [email protected]
TP ThedecreaseinIE1 fromNtoOprimarilyisdueto…
increaseinatomsize
increaseinthenumberofloopsintheatomicorbitals
increaseinelectricalshielding
increaseineffectivenuclearcharge
someotherreason
Response
Counter
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20%
20%
20%
20%
20%
10
69
1.
2.
3.
4.
5.
increaseinatomsize
increaseinthenumberofloopsintheatomicorbitals
increaseinelectricalshielding
increaseineffectivenuclearcharge
someotherreason
Response
Counter
10
70
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Lecture 33 CH101 A1 (MWF 9 am) Fall 2016
Lecture 30 CH101 A2 (MWF 11 am) Fall 2015
2/6/2017 1:13 PM
Copyright © 2015 Dan Dill [email protected]
Quiz ThesteadyincreaseinIE1 fromLitoNe
primarilyisdueto…
20%
20%
20%
20%
20%
1.
2.
3.
4.
5.
Lecture 31 CH101 A2 (MWF 11 am) Fall 2015
Copyright © 2015 Dan Dill [email protected]
Successive ionization energies
Sketchthefirstfiveionizationenergiesofcalcium.
increaseinatomsize
increaseinthenumberofloopsintheatomicorbitals
increaseinelectricalshielding
increaseineffectivenuclearcharge
someotherreason
Response
Counter
Lecture 31 CH101 A2 (MWF 11 am) Fall 2015
10
71
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Successive ionization energies
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Lecture 31 CH101 A2 (MWF 11 am) Fall 2015
Copyright © 2015 Dan Dill [email protected]
Successive ionization energies
IEn (eV)
IEn (eV)
Ca
3p6 4s2
6
Ca
3p6 4s2
6
Ca+
3p6 4s1
12
Ca+
3p6 4s1
12
Ca2+
3p6
51
Ca2+
3p6
51
Ca3+
3p5
67
Ca3+
3p5
67
Ca4+
3p4
85
Ca4+
3p4
85
ThelargestchangefromonetothenextisIE3 – IE2 39eV.
Whyisthischangesolargecomparetotheothersuccessivechanges?
81
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Lecture 33 CH101 A1 (MWF 9 am) Fall 2016
Lecture 31 CH101 A2 (MWF 11 am) Fall 2015
2/6/2017 1:13 PM
Copyright © 2015 Dan Dill [email protected]
Successive ionization energies
Lecture 31 CH101 A2 (MWF 11 am) Fall 2015
Copyright © 2015 Dan Dill [email protected]
Successive ionization energies
IEn (eV)
IEn (eV)
Zeff
Ca
3p6 4s2
6
Ca
3p6 4s2
6
2.7
Ca+
3p6 4s1
12
Ca+
3p6 4s1
12
3.7
Ca2+
3p6
51
Ca2+
3p6
51
5.8
Ca3+
3p5
67
Ca3+
3p5
67
6.7
Ca4+
3p4
85
Ca4+
3p4
85
7.5
IE2 hasn 4,whereasIE3,etc.,haven 3.
ThereisalsoabigchangeinZeff goingfromCa toCa2 .
Fewerloops,lessenergy,moreenergyneededtoionize.
Theelectronsinthe3psubshelldonotshieldoneanother.
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