Molecular Orbital Theory From Concise Inorganic Chemistry by J.D

8/3/2019 Molecular Orbital Theory From Concise Inorganic Chemistry by J.D

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IUOLECULARORBITAL METHODIn the valence ond (clgctronpair) theomadeup of atoms.Elcctrons n atontsocor may not be hybridizcd. f thcy are hysamealom combine o producehybrid effect ively ith orbitals rom other atomThus the atomic()rbit l ls (or thc hybridevenuhen the atom is chcmicallybondeIn the molccular rhital thcorv. he va


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THE Cbe associatedith all tfrom different tomsm

Electronsmaybe coan atommay herefoa wave unction 1r, hElectronsn a molecfunction escribingprocedures:


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LCAO(If one of the wave functions flay s arbother may be either +ve or -ve.) Wavesign may be regarded as waves hat are add up to give a larger resultantwave.Simsigns correspond to waves that are comcanceleach other by destructive nterfere


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l-^:'lIYL I I TH


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IL_____- _

Similarly he energvof t he antibondingmoA. Atomic orbitals nayhold up to two eleopposite pins)and the sameapplies o motwo hvdrogen tomscombining, hereareone from the ls orbital of atom A and oneWhen combined, hese wo electrons othorbital r1r,.,. his results n a savingof ener

LCAO


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THE Coppositesigns his gdensity n betweenhp - p combinationsfConsider irst the compointing long he axantibondingMO arep


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I-C()ccur. c\u l t ing n;t t 'ondingand n* a(Fi-eurc. 9; .Thr'rc arc three points of differenceand th: o orbitalsdescribed reviouslyl . For r overlap he lobesof the atomil ine oining he nuclei.whilst or o ove


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period n the peC:O. This is minvolvedare reof orbitals. Thcbetween diffcreThough these ocentrateelectro


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R!!E: roR _ITNEAR 0\,,


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tq| '

When ), =calledo orb)' : +2 the4. The spinquhave alue

ThePauliex


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EX,\-\lPLESOF N{OLIn the molecular rbitalmethod,we cthan rhe constiruent toms,and usemoorbirals. n rhe build-upof the molecfrom all lhe atoms n the molecule sAulbau principle and Hund's rule are uFor simplicity homonucleardiatomic


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I too | | THEI rv v | |He2+molecule onThis may be consideThereare hrec electr

The fi l led ols bondiols" gives A destab


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EXA.\IPLESOF IV{O

Atomicorbitals Molecularorbitals

,z --l- -:./ o'zs /2 \


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i THEnergy Atomicortitals


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Molecularorbitals

u a /. tt'zpy./>


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TH

EnergY Alomborbitals


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EXAMPLES OF MOLECULThis is showndiagrammaticallyFigure4.2Assuminghat he nnershell oes otpathe bonding nd antibondings evels anpairs emain, iving totalof threebondsvalence ond ormulation sN-N.02 molecule


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@r_ TH:::.:.:.:.:.:' : .:.::::::i:;:i:i:i:i:i:i:

Atcmicorbital


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EXAMPLES OF MOLECUo bond. The effectsof the bondingnZp2cancel, nd hecompletelyilled bondingnfiftedantibondingnlp!, husgivinghalf a n| + ) = l| . Atternatively he bond orde(bonding- antibonding)12,hat is (10 - 7bond that is intermediate.inength betweThe superoxideon has an unpairedetmagnetic.A bondotderof 1l is well acc


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I

EnergyAtomicorbitals

iiiiiiiii,i'iii:i,i


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. I EXAMPLESF MoLECAtomrc rbital Moleculorbilals


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I l 10 | I


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EXAMPLESFMOLEC

Energy Atomicorbitals Molecular'orbitalso'2p,

-iTD^7;q,,i' 'r


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l-u4-theorderof ensincehisonlyrMOs. The moschangedo co+energymore hapart,and he oMos. This l lus


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EXAMPLESOF MOLECULAare equivalent;and the C-O bonds are shsingle valencebond structure such as that sbond lengths,and so fails to describe he struoilc


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rrrrrrr | . t | |The structu

electrons n thatomsand twoOf these,siatoms. Each Oavailable or n


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EXAMPLESOF MOLECotlsr->Themulti-centre MO explanationsasthe valence hell six from S and six fromOf thcse,sixare used o form the o batoms.Each O has our non-bonding l


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tr4The double bodelocalized hree

valenceshell, maThe central Owhich accounts oone of which is atals, each O cont

T


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SUMMARY OF MULTI-CEand involvesmulti-centre molecularo16outer shellelectrons,madeup from sixO atomsand our electronsrom the C atThe C atorn ormso bonds o both theOelectrons. hereare no lone pairsof eleatomsalsouse p hybridorbitals hen hereachO atom,accountingor a further foeightelectrons ltogether,eaying ightele


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Table 4Specie

CozNr


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FURTHE

united atom. Fur ther, the energyof the unithat cf the atomicorbitalsbecause f the gre:..1e,-ularorbitals are in an intermediatepo:ie united atom and those n the separateatothe energiesof the electrons n the separate(rhat s a graph of internalenergyagainst hfrom r = 0 to r : co),a correlationdiagram

Molecular Orbital Theory From Concise Inorganic Chemistry by J.D

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Transcript of Molecular Orbital Theory From Concise Inorganic Chemistry by J.D