7 lebxz - zi`etx eia dqcpdl dinik oxe` lh :zlbxzn 9.11.009,mihehxqd lk z` zllek `l `id.zi`etx-eia dqcpdl dinika lebxz jldna dclwed ef zxagn.iyi`d mkyeniyl as-is zwteqn zxagnd.zeirh e` miweic-i` lelkl dlelre.amnonar@bgu.ac.il l gelyl mipnfen mz` zexrde zex`d ixlewlen dpan 1 valence Bond - ikxrd xywd ziixe`z 1.1 zeinh` ec zelewlen xear 1.1.1 y jk.mitteg mineh` ipy ly zipevig dtilwa mi`ln ivg mineh` milhiaxe` xy`k mixvep mixyw.dititgd lhiaxe` z` miqlk`n,meh` lkn cg`,mipexhwl`d σ(s,s) H + H H H :ze`nbec.1 H + [He]s p 5.. F :.. H σ(s,p) F. σ(p,p) F + F F F.3 mihpleed mipexhwl`d ly mineh` milhiaxe` zititgn mixlewlen milhiaxe` zxivi - ihpleew xyw.zeineh` ax zelewlen xear caer `l z`fd dhiyd.mibeefn `ld oineh` milhiaxe` ly (d`lkd) divficixaid - zeineh` ax zelewlen xear 1.1. -ixaid zilhiaxe` zlawl mipey mineh` milhiaxe` z`lkd - milhiaxe` ly divficixaid 1.1 dxcbd miaaxrn,mze` mixxern,iceqid mavna mi`vnpy mineh` milhiaxe` migwel.midf (mi`lken) mic.(micixaid) mi`lken milhiaxe` mi`xwpd miycg milhiaxe` mixveie.mze` ep`lkd mze` milhiaxe`d xtqnl deey d`lkda mixvepy mihliaxe`d xtqn 1. dxrd (geexa) zxfgen `id j`,mipexhwl`d z` xxerl ick dibxp` zrwyen divficixaidd jldna 1.3 dxrd.xywd zxivi i"r 1
.mineh`d milhiaxe`d ly dibxp`d ikxr oia z`vnp miicixaidd milhiaxe`d zibxp` 1.4 dxrd CH 4 :`nbec H : C : s sp,mi`ln ivgd p d ilhiaxe`n cg` lka mipexhwl` ipy wx qpkdl mixen` eid,zncewd dixe`zd t"r :okl.zltep zncewd dixe`zd okl.daivi `l ce`n `ide,raha zniiwy dlewlen `l `id CH la` H : C : s sp e C : s 1 p 3 4 sp 3 `xwi H d zrax` n cg` lkl C oia xyw lkle.sp 3 beqn midf milhiaxe` 4 mixvep d`lkd ixg`.σ ( sp 3, s ) xywd bec - σ ifkxnd meh`d ly lhiaxe` - sp 3 Cl : 3s 3p 5 B : s p 1 e B : s 1 p 3 sp H : N : s p 3 4 sp 3 ifkxnl xeywd meh`d ly lhiaxe` - s. sp oial s oia didi sp 3 ly ihbxp`d mewind BCl 3 :`nbec σ ( sp, p ) `xwi xywd NH 3 :`nbec cg` lk miqlke`n xak p ilhiaxe` lk lk,mewn zeptl ick xg` lhiaxe`l utew `l oexhwl` dt H mr cgia.ccea mipexhwl` bef ly `l`,xeyw `l didi mixywd zrax`n cg`.cg` oexhwl`a.mixyew izla mipexhwl` bef mr zief my -ne`ibd dixh { sp 3 } `ln lhiaxe` cere σ ( sp 3, s ) midf mixyw dyely exveei SN VSEPR mitzzyny milhiaxe` divficixaid zexrd 180 zix`pil AX 1 s, 1 p sp mixzep p ilhiaxe` 10 yleyn etzzyd `ly divficixaida 3 AX 3 1 s, p sp lhiaxe` xzep ixeyin cg` p 109.5 xcdxhh 4 AX 4 1 s, 3 p sp 3 mixzep `l 10, 90 -ia dcinxit zyleyn 5 AX 5 1 s, 3 p, 1 d sp 3 d 90 xcdhwe` 6 AX 6 1 s, 3 p, d sp 3 d 90 dcinxit zireaix 90 raexn ixeyin p ilhiaxe` 6 AX 5 E 1 s, 3 p, 1 d sp 3 d zexfbp zexev 6 AX 4 E 1 s, 3 p, 1 d sp 3 d
dlahd t"r okle SN = 4 xnelk,mixyw 4 yi C lkl,qi`el z`gqep ly dnxb`ic itl,c H 6 :`nbec didi C d ipy oia xywde,σ ( sp 3, s ) didi C mr H lk ly xywd okle.sp 3 `id C ly divficixaidd σ ( sp 3, sp 3) okle ( miccea mipexhwl` zebef ly ) mixyw 4 yi qi`el z`gqep ly dnxb`ic itl.h O :`nbec.{ sp 3 } miccead zebefd ipye σ ( sp 3, s ) didi H l O oia mixywde sp 3 didz divficixaidd f`e SN = 4 lk mipexhwl` ipy eliki xaky milhiaxe` ipy cere ( mipnind mr) miipy `l`,mixyw 4 mixvep `l.cg` mipirxbd ipy oiay xywd xiv jxe`l mitteg milhiaxe`d eay ihpleew xyw `ed - σ xyw 1.5 dxcbd.mipirxbd ipy oiay xef`a ziaxin `id zipexhwl`d zetitvd df xywa xnelk,mixeywd mineh`d ly ipya mitteg d`lkda mitzzyn `ly p ilhiaxe` ipy eay ihpleew xyw `ed - π xyw 1.6 dxcbd.dlewlend xeyinl zgzn ipyde,lrn cg`.mixeyin π xyw + σ xyw - letk xyw 1.7 dxcbd π ixyw + σ xyw - yleyn xyw 1.8 dxcbd xyw yi H lkl xnelk.(zix`pil) sp `id divficixaidd okle SN =,C lkl aiaqn.c H :`nbec dn cg` mr cg` lk) mixvei,mixzepd p d ilhixe` ipye.cg` σ (sp, sp) xyw yi C d ipy oiae.σ (sp, s) rvan miyleyn e` miletk mixyw zlleky dlewlena ifkxnd meh`d xnelk.π (p, p) ixyw ipy ( ipydc.mi`lken `l p ilhiaxe` zitittgn mixvep π ixywe σ ixywa etzzydy milhiaxe`d ly divficixaid :mixyw ipy eidi okle.dpey`xd dixe`izl mixfeg,dheyt zineh` ec dlewlen efy llba,o :`nbec.π (p, p) e σ (p, p).π (p, p) ipye σ (p, p) :mixyw dyely N :`nbec mixlewlend milhiaxe`d zixe`iz 1..zlaewn xzei meik `ide.divficixaidd ziixe`z z` dtilgnd ztqep dixe`z `id efd dixe`zd lhiaxe` lk.mipexhwl` `evnl ddeab zexazqd yi ea dlewlena xef` - ixlewlen lhiaxe` 1.9 dxcbd.mipexhwl` ipy cr likdl leki ixlewlen mineh`d milhiaxe`d ly zix`pil divpianew 1..1 :mixlewlen milhiaxe` mixvep mineh` milhiaxe` ipy xeaiga.mipirxbd ipy oia ddeab zipexhwl` zeititv yi,dkenp dibxp` lra - xyew lhiaxe` - σ.1.mipirxbd oia dkenp zipexhwl` zetitv yi,ddeab dibxp` lra - xyew ihp` lhiaxe` - σ..dtitgd ixef` xeqig - σ,dtitgd ixef` xeaig -σ -lena mineh` lhiaxe` - non-bonding orbital - ( iyily lhiaxe` beq) xyew `l hliaxe` 1.10 dxcbd.ineh` lhiaxe`k eizepekz z` xneyd dlew Atomic Orbital - AO Molecule Orbital - MO.mze` exviy AOs y xtqn = MOs d xtqn E MO bonding < E AO < E MO anti bonding mixlewlen milhiaxe` lr milg epcnly millkd 3 mipexhwl`d ielin oexwir.1 3
ile`t oexwir. cped llk.3 `lnziy iptl ( cr) mipexhwl` `lnzi `ed,xzei dkenp dibxp` lra `ed xyew lhiaxe`y llba.xyew ihp`d lhiaxe`d BO - Bond Order - xyw xcq 1.11 dxcbd BO = 1 (#bonding electrons #anti-bonding electrons).minly `l mikxr mb lawl leki BO d okl xyewd lhiaxe`d z` `lniy mipexhwl` ipy yi H :`nbecl BO = 1 ( 0) = 1 zipexhwl`d ziivxebitpwed.( ccea xyw yi ea) qi`el znxb`icl mb mi`zny dn.1 xyw xcq xnelk (σ1s) (σ 1s) 0 `id H ly :ixlewlen lhiaxe`a mixyw xe`izl millk.π xywn wfg σ xyw.1.daivi xzei dlewlend - wfg xzei xywd - lecb xzei BO y lkk.,mixyewd mipexhwl`d xtqnn lecb e` deey mixyew izlad mipexhwl`d xtqn f` BO 0 m`.3.miiwzz `le daivi didz `l dlewlend xnelk dxcbd 1.1 HOMO - highest occupied MO - mipexhwl` qlk`ny deab ikd ixlewlend lhiaxe`d dxcbd 1.13 LUMO - Lowest Uoccupied MO - mipexhwl` qlk`n `ly jenp ikd ixlewlend lhiaxe`d :(Z 7 ) mixlewlend miliaxe`d ly (deabl jenpdn) ihbxp`d xcqd σs.1 σ s. πpy e πpx.3 σpz.4 π py e π px.5 σ pz.6.mitlgzn 4 e 3 f` Z 8 xy`k (σs) (σ s) (πpx) 1 (πpy) 1 :`id B ly zineh`d dvxeibitpwed :`nbec BO = 1 (4 ) = 1 4
i"r zkynp `id okl - dlewlena mibeefn izla mipexhwl` miniiw - zihpbnxt dlewlen 1.14 dxcbd.ihpbn dcy okl - mibeefn izla mipexhwl` miniiw `le mibeefn mipexhwl`d lk - zihpbn`ic dlewlen 1.15 dxcbd.ihpbn dcy i"r zkynp `l `id.mibeefn `l mipexhbl` ipy yi ik zihpbnxt dlewlen `id ( mcewn) B dlewlend :`nbec.(5+5) zeikxr ipexhwl` 10 yi :N dlewlen :`nbec : zipexhwl`d divxebitpewd.1 (σs) (σ s) (πpx) (πpy) (σpz) :daivi m`d. BO = 1 (8 ) = 3 ce`n daivi zihpbn`ic -?zihpbn`ic/zihpbnxt.3 HOMO σpz.4 LUMO π p 5