Lecture 1 CH102 A1 (MWF 9:05 am) Spring 2017
Lecture 1 CH102 A1 (MWF 9:05 am) Spring 2017
1/23/2017 1:28 PM
Copyright © 2017 Dan Dill [email protected]
TP AtomXhaveIEX 13eV andatomYhasIEY 15eV.
ComparedtomoleculeX:H,…
20%
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20%
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Lecture 1 CH102 A1 (MWF 9:05 am)
Friday, January 20, 2017
• Review:Whenatomsaredifferent,whichAOsmakeMOs
• WhichAO’scombine:Symmetry,overlap,energy
• MOdescriptionofhydroxide,OH
moleculeY:Hhasa greater dipolemoment
moleculeY:Hhasthesamedipolemoment
moleculeY:Hhasasmaller dipolemoment
Neithermoleculeispolar
Cannotknowrelativepolaritywithoutknowingthe
electronegativitiesofatomsH,X,andY.
Next:Continue“HybridAOsandPolyatomicMOs",http://goo.gl/6hBD8X :
MOdescriptionofwater.HybridAOs.HybridAO‐MOdescriptionofwater.
Ethane,H3C‐CH3
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Lecture 1 CH102 A1 (MWF 9:05 am) Spring 2017
Copyright © 2017 Dan Dill [email protected]
Lecture 1 CH102 A1 (MWF 9:05 am) Spring 2017
Copyright © 2017 Dan Dill [email protected]
When atoms are different, which AOs combine?
Orbital size and shielding
AOsthathavenetoverlap.
Whenthereismorethanoneelectron,theone‐electron‐atomenergyformula
canbegeneralizedto
ThisalwaysmeansonlyvalenceAOs,
Orbitalenergy 13.6eVZeff2/n2
becausetheinner‐shellAOsaretoosmall,
whereZeff istheeffectivenuclearcharge.
becauseoftheirmuchlargerZeff electroncloudverysmall
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Copyright © 2017 Dan Dill [email protected]
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Lecture 1 CH102 A1 (MWF 9:05 am) Spring 2017
Lecture 1 CH102 A1 (MWF 9:05 am) Spring 2017
1/23/2017 1:28 PM
Copyright © 2017 Dan Dill [email protected]
Lecture 1 CH102 A1 (MWF 9:05 am) Spring 2017
Orbital size and shielding
Orbital size and shielding
Theapproximatesizeoftheorbitalis
Theionizationenergyoftheorbitalis
Orbitalsize 50pmn2/Zeff
IEorbital E∞ Copyright © 2017 Dan Dill [email protected]
13.6eVZeff2/n2 0 13.6eVZeff2/n2
13.6eVZeff2/n2
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Lecture 1 CH102 A1 (MWF 9:05 am) Spring 2017
Copyright © 2017 Dan Dill [email protected]
1s clouds much smaller than 2s clouds
Lecture 1 CH102 A1 (MWF 9:05 am) Spring 2017
Copyright © 2017 Dan Dill [email protected]
At maximum 2s bonding, no 1s bonding
http://quantum.bu.edu/CDF/101/Li2Bonding1sAnd2sElectronClouds.cdf
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Copyright © 2017 Dan Dill [email protected]
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http://quantum.bu.edu/CDF/101/Li2Bonding1sAnd2sElectronClouds.cdf
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Lecture 1 CH102 A1 (MWF 9:05 am) Spring 2017
Lecture 1 CH102 A1 (MWF 9:05 am) Spring 2017
1/23/2017 1:28 PM
Copyright © 2017 Dan Dill [email protected]
At maximum 2s antibonding, no 1s antibonding
http://quantum.bu.edu/CDF/101/Li2Antibonding1sAnd2sElectronClouds.cdf
Lecture 1 CH102 A1 (MWF 9:05 am) Spring 2017
Only valence AOs effect bonding/antibonding
http://quantum.bu.edu/CDF/101/Li2BondingAndAntibonding2sElectronClouds.cdf
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Lecture 1 CH102 A1 (MWF 9:05 am) Spring 2017
Copyright © 2017 Dan Dill [email protected]
Copyright © 2017 Dan Dill [email protected]
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Lecture 1 CH102 A1 (MWF 9:05 am) Spring 2017
Copyright © 2017 Dan Dill [email protected]
Only valence AOs effect bonding/antibonding
When atoms are different, which AOs combine?
HereisthecorrelationdiagramwehaveseenforLi2 fig10.22,p402 .
SOE:Symmetry,Overlap,Energy
• Symmetry:WhichAOshavenonzerooverlap?
• Overlap:WhichAOscombinewiththegreatestbonding/antibondingeffect?
• Energy:HowdoesrelativeAOenergyaffectcompositionofMOs?
Sketchamorecorrectversion.
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Copyright © 2017 Dan Dill [email protected]
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Lecture 1 CH102 A1 (MWF 9:05 am) Spring 2017
Lecture 1 CH102 A1 (MWF 9:05 am) Spring 2017
1/23/2017 1:28 PM
Copyright © 2017 Dan Dill [email protected]
Lecture 1 CH102 A1 (MWF 9:05 am) Spring 2017
Copyright © 2017 Dan Dill [email protected]
Symmetry: Net overlap or not?
Overlap: Greater the better
• ForapairofAO’stogivea bonding/antibonding pairofMO’s,theremustbe
netoverlap netin‐phaseornetout‐of‐phase .
• Ifin‐phaseandoutofphaseoverlapexactlycancel,theAO’sremain
uncombined,asnonbondingorbitals.
• Themorenetoverlap,thegreaterthebonding/antibondingeffect.
• CoreAO’shaveleastnegligibleoverlap,soignore
• OnlyvalenceAO’shavesignificantoverlap
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Lecture 1 CH102 A1 (MWF 9:05 am) Spring 2017
Copyright © 2017 Dan Dill [email protected]
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Lecture 1 CH102 A1 (MWF 9:05 am) Spring 2017
Energy: Closer the better
TP AtomXhaveIEX 13eV andatomYhasIEY 15eV.
ComparedtomoleculeX:H,…
• Thecloser AO’sareinenergy,thegreater thebonding/antibondingeffect.
• IfAO’shavesameenergy identicalatoms,homonuclearbond ,MO’swillbe50%
ofeachAO.
• IfAO’shavedifferentenergy differentatoms,heteronuclearbond ,…
• BondingMO containsmoreofthelowerenergyAO
• AntibondingMO containsmoreofthehigherenergyAO
20%
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Copyright © 2017 Dan Dill [email protected]
1.
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Copyright © 2017 Dan Dill [email protected]
moleculeY:Hhasa greater dipolemoment
moleculeY:Hhasthesamedipolemoment
moleculeY:Hhasasmaller dipolemoment
Neithermoleculeispolar
Cannotknowrelativepolaritywithoutknowingthe
electronegativitiesofatomsH,X,andY.
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Lecture 1 CH102 A1 (MWF 9:05 am) Spring 2017
Lecture 1 CH102 A1 (MWF 9:05 am) Spring 2017
1/23/2017 1:28 PM
Copyright © 2017 Dan Dill [email protected]
Energy: Closer the better
Lecture 1 CH102 A1 (MWF 9:05 am) Spring 2017
Energy: Closer the better
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Lecture 1 CH102 A1 (MWF 9:05 am) Spring 2017
Copyright © 2017 Dan Dill [email protected]
Copyright © 2017 Dan Dill [email protected]
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Lecture 1 CH102 A1 (MWF 9:05 am) Spring 2017
Copyright © 2017 Dan Dill [email protected]
Sketch the AO-MO correlation diagram of HO−
Note:IEO IEH
MOdescriptionofwater
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Copyright © 2017 Dan Dill [email protected]
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Lecture 1 CH102 A1 (MWF 9:05 am) Spring 2017
Lecture 1 CH102 A1 (MWF 9:05 am) Spring 2017
1/23/2017 1:28 PM
Copyright © 2017 Dan Dill [email protected]
Sketch the AO-MO correlation diagram of HO−
Lecture 1 CH102 A1 (MWF 9:05 am) Spring 2017
Copyright © 2017 Dan Dill [email protected]
Sketch the AO-MO correlation diagram of HO−
WhyistheO2sAOnonbonding?
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Lecture 1 CH102 A1 (MWF 9:05 am) Spring 2017
26
Copyright © 2017 Dan Dill [email protected]
Sketch the AO-MO correlation diagram of HO−
WhyaretwooftheO2pAOsnonbonding?
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Copyright © 2017 Dan Dill [email protected]
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