WPC-   sYEXrDM9lzͱ g6h Yې=*M'I/A&⛑/v|3)4 PYÆ ?x`U^TYtG^q.lf+uvѠyԽiUp<yJ`m~E #ﳍSZb  `#T%X蘄 14!5$ÿTmZkK^x%Xz@V2+"L &f ĺdAMW?j0nZ qTG8rt hރGpԚ(~09sthZ3W@@;3ckLݴ#F9˾,l ܿd1+5Swn߅iQ¼A'݈9,h< yvxF'7x}y";U>:x 0Z 0 0 0 0 0 0 0  0  0 0z 0_ 0D 0& 0 0 0 0 0~ 0e 0I 0- 0 0 0 0 0 0a UJ:4" 0<n" 0'" 0 # 0$ 0& 1U' 7 'U,( 1g/( 7( 1c( 7)) 0%)#)UN+ %+M,(,N., 1u0, 72,^ ,w,4,, m,\  `&Times New Roman' CHAPTER 4 susie0Giordano .   2P+M 0_level1  , 8.4 <DL!823  ..  5+ 4 <DL!5  2M+M 0_level2  X 5+4 44 <DL!523  ..  5+ 4 <DL!5  2M+M 0_level3   5+` ` ` <DL!523  ..  5+ 4 <DL!5  2J+M 0_level4   2( <DL!223  ..  5+ 4 <DL!5  2J+M 0_level5   2( <DL!223  ..  5+ 4 <DL!5  2G+M 0_level6   /% <DL!/23  ..  5+ 4 <DL!5  2G+M 0_level7  4 /% <DL!/23  ..  5+ 4 <DL!5  2D+M 0_level8  ` ,"< <<DL!,23  ..  5+ 4 <DL!5  2D+M 0_level9   ,"h hhDL!,23  ..  5+ 4 <DL!5  2PM 0_levsl1  , 8.4 <DL!823  Ԁ  5+ 4 <DL!5  2MM 0_levsl2  X 5+4 44 <DL!523  Ԁ  5+ 4 <DL!5  2MM 0_levsl3   5+` ` ` <DL!523  Ԁ  5+ 4 <DL!5  2JM 0_levsl4   2( <DL!223  Ԁ  5+ 4 <DL!5  2JM 0_levsl5   2( <DL!223  Ԁ  5+ 4 <DL!5  2GM 0_levsl6   /% <DL!/23  Ԁ  5+ 4 <DL!5  2GM 0_levsl7  4 /% <DL!/23  Ԁ  5+ 4 <DL!5  2DM 0_levsl8  ` ,"< <<DL!,23  Ԁ  5+ 4 <DL!5  2DM 0_levsl9   ,"h hhDL!,23  Ԁ  5+ 4 <DL!5  2PM 0_levnl1  , 8.4 <DL!823   5+ 4 <DL!5  2MM 0_levnl2  X 5+4 44 <DL!523   5+ 4 <DL!5  2MM 0_levnl3   5+` ` ` <DL!523   5+ 4 <DL!5  2JM 0_levnl4   2( <DL!223   5+ 4 <DL!5  2JM 0_levnl5   2( <DL!223   5+ 4 <DL!5  2GM 0_levnl6   /% <DL!/23   5+ 4 <DL!5  2GM 0_levnl7  4 /% <DL!/23   5+ 4 <DL!5  2DM 0_levnl8  ` ,"< <<DL!,23   5+ 4 <DL!5  2DM 0_levnl9   ,"h hhDL!,23   5+ 4 <DL!5  6 4Heading 1 P  CE O* `"Comic Sans MSO  2( <DL!2    5+ 4 <DL!5XXXS\  `&Times New RomanS P  CE * `"Comic Sans MS<:Default Para.|} ,Title   O* `"Comic Sans MSO     XXXS\  `&Times New RomanS 6nr 4Body TextO* `"Comic Sans MSO XXXS\  `&Times New RomanS < :Body Text In > O* `"Comic Sans MSO  8.4 <DL!8  5+ 4 <DL!5XXXS\  `&Times New RomanS > :hl 8Body Text 2O* `"Comic Sans MSOXXXS\  `&Times New RomanS 359=AEIMQ1 o o o% (\ Y`Symbol 35=CIOU[a2(a)a.i.1.a.i.1.a.( i. 35;?EKQW]31.-i.1.a.i.1.a.* i.#|x($..      CEUS.,/X=XX/XX=XX/X=Lexmark 3200 Series ColorFinePX,,,,PX0(9 Z6Times New Roman Regular/X3#37=CIQYag1.a.i.(1)(a)(i)1)a)4i)HN- TI-relCORE| U -!..      CEUS.,/X=XX/XX=XX/X=  _       ! jXX=  j     !   CHAPTER4.4:POLARMOLECULES! v݌  Ќ  XaX X=XXXa   XXX=8X % (034""  ,B.4 <DL!XB  X,E(4 4 <DL!4X!E'_ 82 3   4   8 '_Chemistsbelievethatmoleculesaremadeupofcharged  particles(electronandnuclei)݌ /B Ќ X! X44X!!   ""  ,B.4 <DL!XB  X,E(4 4 <DL!4X!E'_ 8>2 3   4   8 '_Amoleculeisconsideredtobe polar ortohavea molecular t  polarity, whenthemoleculehasanoverallimbalanceof   charge.>;݌    Ќ X! X44X!!   ""  ,B.4 <DL!XB  X,E(4 4 <DL!4X!E'_ 82 3   4   8 '_Thatis,themoleculehasaregionwithapartialpositive C V  charge,andaregionwithapartialnegativecharge.݌   Ќ X! X44X!!   ""  ,B.4 <DL!XB  X,E(4 4 <DL!4X!E'_ 8$ 2 3   4   8 '_Notallmoleculeswithpolarbondsarepolarmolecules.$ ! ݌   Ќ X! X44X!!   X?+4 44 <DL!X?Eg.AcarbondioxidemoleculehastwopolarC=Obonds,but Wj  itisnotapolarmolecule.   ̀AwatermoleculehastwopolarOHbonds,anditisa  polarmolecule.  Howdoyoupredictwhetherornotamoleculethatcontains '$ polarbondshasanoverallmolecularpolarity? 1)D&   +(  Todeterminemolecularpolarity,youmustconsiderthe  shapeofthemoleculeandthebond dipoles withinthe 2E molecule. w  Beforewecontinuediscussingthedipolenatureofa  molecule,letusgobackanddeterminewhatismeantbythe F Y dipolenatureofamolecule.    ELECTRONEGATIVITYANDPOLARITYOFBONDS:  Zm  / /""  ,XH.4 <DL!444X!H  ,B% <DL!4X!B'_ 8<2 3     8 '_LinusPaulingrealizedthatwhiletwoatomscanshare )<  oneormorepairsofelectrons,thereisnothingthat n  requiresthemtosharethoseelectronpairsequally.<<݌  Ќ X'444X!  X!'   ""  ,XH.4 <DL!444X!H  ,B% <DL!4X!B'_ 82 3     8 '_Hesawtheneedforatheorytoexplainandpredict   thepolarityofmoleculesandsocombinedproperties =P suchasbondenergieswithvalencebondtheoryto  createanewpropertyofatomscalled   electronegativity. ݌   Ќ X'444X!  X!'   XE+ 4 <DL!444X!E  " 9" DL!X!9Ӏ Electronegativity: isameasureofhowstronglyanatom  attractselectronsinachemicalbond  3 (the  hog ). e!x XaX8 "  #  / /""  ," K.4 <DL!X!K  ,B% <DL!4X!B8XXa'_ 82 3     8 '_BecausePaulingscalculationsproduceddifferencesin $! theattractionofnucleiforasharedpairofelectrons &.# inacovalentbond,hearbitrarilyassignedvaluesso `'s$ that fluorine, themostelectronegativeatom,hada (% valueofabout4.0.݌ )& Ќ " -X!  X!-   ""  ," K.4 <DL!X!K  ,B% <DL!4X!B'_ 8)2 3     8 '_Allotheratomshavealowerelectronegativityand, /+B(  therefore,alowerattractionforelectronswhen t,)! bonded.),݌ -*" Ќ " -X!  X!-    " H+ 4 <DL!X!H .,# Drawtheperiodictableandindicate,witharrows,thetrendthat  occurs(page252,fig.2) 2E / /""  ,E.4 <DL!X!E  ,B% <DL!4X!B'_ 82 3     8 '_Paulingusedthedifferenceinelectronegativityto F Y explainpolarityofachemicalbond.݌   Ќ ' X!  X!'   ""  ,E.4 <DL!X!E  ,B% <DL!4X!B'_ 8!!2 3     8 '_Thegreaterthedifferenceinelectronegativity,the   morepolarthebond.!!"݌  (  Ќ ' X!  X!'   ""  ,E.4 <DL!X!E  ,B% <DL!4X!B'_ 8^#2 3     8 '_Thesmallerthedifference,themorenonpolarthe Zm  bond.^#[$݌   Ќ ' X!  X!'   ""  ,E.4 <DL!X!E  ,B% <DL!4X!B'_ 8%2 3     8 '_Avery polarbond isan ionicbond. %&݌   Ќ ' X!  X!'   ""  ,E.4 <DL!X!E  ,B% <DL!4X!B'_ 8'2 3     8 '_A nonpolarbond isa covalentbond. '(݌ )<  Ќ ' X!  X!'   ""  ,E.4 <DL!X!E  ,B% <DL!4X!B'_ 8)2 3     8 '_Asomewhatpolarbondisa polarcovalentbond. )*݌ n  Ќ ' X!  X!'   ""  ,E.4 <DL!X!E  ,B% <DL!4X!B'_ 8+2 3     8 '_Whentwodifferentkindsofatoms(usuallytwonon  metals)sharetheirelectronstoformabondthere   maybe unequalsharing betweenthetwoduetotheir =P electronegativities.+,݌  Ќ ' X!  X!'   ""  ,E.4 <DL!X!E  ,B% <DL!4X!B'_ 8.2 3     8 '_Thismeansthatthe electronsspendmoreoftheir  timeclosertooneatomicnucleusthattheother. ./݌   Ќ ' X!  X!'   ""  ,E.4 <DL!X!E  ,B% <DL!4X!B'_ 802 3     8 '_Theendofthebondwherethenegativelycharged Qd electronsspendmoretimeislabelledasbeing  partiallynegative().01݌  Ќ ' X!  X!'   " "  ,E.4 <DL!X!E  ,B% <DL!4X!B'_ 8k32 3     8 '_Theendofthebondthatispartiallypositiveis  3 labelled().Observefig.3page252.k3h4݌ e!x Ќ ' X!  X!'   " "  ,E.4 <DL!X!E  ,B% <DL!4X!B'_ 852 3     8 '_Thus,everypolarbondhasa bonddipole: apartial " negativechargeandapartialpositivecharge, #! separatedbythelengthofthebond.56݌ 4%G" Ќ ' X!  X!'     .*+"  P ?( <DL!X!?j" 8Figure:Dipolesareoftenrepresentedusing   vectors.Vectorsarearrowsthat  havedirectionandlocationinspace.   ]p  PPCECE.,8 j"88 B( <DL!  X!B    &  9  PartialpositivechargePartialnegativecharge9:  :Ԍ - @ Ќ *  X!  X!*j" 8j"  j" PPCE.,CE.,  B( <DL!  X!B'- : r     ЀC=O    Wj   ':   PPCECE.,8 j"88 B( <DL!  X!B    &  <  Dipolevectorpointsfrompositivechargetonegativecharge<=  =Ԍ    Ќ *  X!  X!*j" 8j"  j" PPCE.,CE.,  B( <DL!  X!B'= <O     / /"" P ,H.4 <DL!  X!H  ,B% <DL!4X!B8 j"'_ 8?2 3     8 '_Otherexamplesofpolarcovalentbondsinclude: Qd  CO,OHandNH.?@݌  Ќ *  X!  X!* P  "" P ,H.4 <DL!  X!H  ,B% <DL!4X!B'_ 8 B2 3     8 '_Carbonandhydrogenattractelectronstoalmost  thesamedegree. B C݌  3 Ќ *  X!  X!* P  "" P ,H.4 <DL!  X!H  ,B% <DL!4X!B'_ 8DD2 3     8 '_Therefore,whencarbonisbondedtoanother ex carbonatomortoahydrogenatom,thebondis  notusuallyconsideredtobepolar.DDDE݌  Ќ *  X!  X!* P  P E+ 4 <DL!  X!EToanswerthequestionabove: y" "8888   "dG  Ifequalbonddipolesactinoppositedirectionsinthree %" dimensionalspace,theycounteracteachother."dGG݌ H&[# Ќ8888   Amoleculewithidenticalpolarbondsthatpointinopposite (% directionsisnotpolar. **' "8888   "\I  Ifthebonddipolesinamoleculedonotcounteracteachother ,) exactly,themoleculeispolar."\II݌ -* Ќ8888   P ?( <DL!X!?Question: +/>, Ї ( (00% / /"" P ,H.4 <DL!  X!H   ,E( <DL!4X!EK2(  a  )3     Determinewhetherthefollowingmoleculesarepolaror  nonpolar.Justifyyouranswer.KL݌ 2E Ќ *  X!  X!* P  >P H.4 <DL!  X!H w Ѐ(a)CCl4󀀀(b)CCl3H(c)BeF2󀀀(d)HCl     F Y  * (00( "" > ,K.4 <DL!4X!K  ,E(f f <DL!4X!EO2  2  .3   f   Whichofthefollowingismorepolar?Justifyyouranswer.OP݌   Ќ -4X!ff X!- >  > H+ 4 <DL!4X!H B+f ff <DL!X!B(a)NF3orNCl3󀀀(b)Icl4orTeCl4  (   % (00* / /""  ,K.4 <DL!fff X!K  X,E(4 4 <DL!4X!E'_ 8|S2 3   4   8 '_Paulingliketothinkofchemicalbondsasbeingdifferentin   degreeratherthandifferentinkind.|ST݌ )<  Ќ X*fff X!44X!*   ""  ,K.4 <DL!fff X!K  X,E(4 4 <DL!4X!E'_ 8U2 3   4   8 '_Tohim,allchemicalbondsinvolvedasharingofelectrons, n  evenionicbonds.UV݌  Ќ X*fff X!44X!*   ""  ,K.4 <DL!fff X!K  X,E(4 4 <DL!4X!E'_ 8*X2 3   4   8 '_Thedegreeofsharingdependsuponthedifferencein   electronegativitiesofthebondedatoms.*X0Y݌ =P Ќ X*fff X!44X!*   H+ 4 <DL!fff X!H̀Percentioniccharacter Qd ̀IonicPolarCovalentCovalent " ̀ElectronegativityDifference +(  Whatifyouknowtheformulaofacompoundbutdonotknowhow ,)!  toclassifyit?Inthiscase,youcanusetheelectronegativity .*+" differencebetweenthebondingatomstopredictthetypeof  bond. 2E  Eg.Twoatomswithidenticalelectronegativities,suchaschlorine  ('_ 8D 8 '_EN=3.163.16=0)shareelectronsequally.Theyarebonded  covalently. F Y Whentwoatomshavedifferentelectronegativities,theatom   withthehigherelectronegativityvalueattractselectronsmore  (  stronglythantheatomwiththelowerelectronegativityvalue. Zm  Insodiumchloride,forinstance,chlorine(EN=3.16)attractsan   electronmorestronglythansodium(EN=0.93).Therefore, )<  sodiumsvalenceelectronhasaveryhighprobabilityofbeing n  foundnearchlorine,andaverylowprobabilityofbeingfound  nearsodium.Ahighelectronegativitydifferenceis   characteristicofioniccompounds. =P ̀'_ 8D 8 '_EN=3.16!0.93  Ѐ   Ѐ=2.23 Qd Accordingtothescalegivenabove,thissubstancecanbe  classifiedasionic.  3 Letustrytopredictwhetherasubstanceispolarornonpolar #! withoutusingthevaluesofelectronegativities. 4%G"  B+f ff <DL!X!B$8888  $c  Boththeshapeofthemoleculeandthepolarityofthebondsare ,)! necessarytodetermineifamoleculeispolarornonpolar.$c}c݌ .*+" Ќ8888  > K.4 <DL!fff X!K \/o,#  > H+ 4 <DL!4X!HLetusobservethemethanemolecule(CH4). 2E MethaneisanonpolarsubstanceanditsCHbondsarepolar. n  Theshapediagramwithbonddipolesshowsthattheouterpart  ofthemoleculeisuniformlypositiveandthereforethemolecule   hasnoendsthatarechargeddifferently.Anearbymolecule =P would seethesamechargefromallsidesofthemethane  molecule.ThisistruebecausetheCH4moleculeis symmetrical.   Infact,allsymmetricalmoleculesarenonpolarforthisreason.   "8888   "1h  Inallsymmetricalmolecules,thesumofthebonddipolesis  3 zeroandthemoleculeisnonpolar."1hh݌ e!x Ќ8888   ̀$8888  $i  Question:$ij݌ +(  Ќ8888  Predictthepolarityoftheammonia,NH3,molecule,includingyour .*+" reasoning. \/o,# ЇStep1:   * (00% XaX8X=XXXa""  XB+4 44 <DL!X!B  X?% <DL!444X!?k2-3     XXX=8XdrawtheLewisstructurekl݌ 2E Ќ ' X!  X!'   Step2: Zm  XaX8X=XXXa""  XB+4 44 <DL!X!B  X?% <DL!444X!?On2-3     XXX=8XbasedontheLewisstructure,drawtheshapediagramOn'o݌   Ќ ' X!  X!'   Step3:   ̀addtheelectronegativitiesoftheatoms,fromthe  periodictable,andassignandtothebonds.  Step4: H*[' XaX8X=XXXa""  XB+4 44 <DL!X!B  X?% <DL!444X!?q2-3     XXX=8Xdrawinthebonddipolesqbr݌ ,)! Ќ ' X!  X!'    \/o,# ЇTheammoniamoleculeispolarbecauseithaspolarbondsthatdo Zm  notcanceltozero.Theelectronpairsareinatetrahedral   arrangement,butoneofthesepairsisalonepairandthreeare   bondingpairs.Therefore,thebonddipolesdonotcancel. )<  PracticeProblems:Page255256 =P ̀#6(a)(b),7(a)(c)(d),8(b)(d),10  Questions:Page256 Qd ̀#1(a)(b)(e),2(a)(b)(e),3(a)(b)  XaX8X=XXXa