BAI4lien Ket Hoa Hocppt

Chng 4: Lin kt ha hc v cu to phn tHA I CNG

Chemistry 140 Fall 2002 Dutton

Ni dungNhng khi nim c bn v lin kt ha hcLin kt ionLin kt cng ha trLin kt kim loiLin kt hyroLin kt Van Der VaalBi tp


4.1 Nhng khi nim c bn v lin kt ho hc4.1.1 Bn cht ca lin kt. Theo quan im hin i cc loi lin kt ho hc u c bn cht in v suy cho cng l do tng tc ca cc ht mang in l ht nhn nguyn t v electron Trong lin kt ha hc ch c electron ca cc phn lp ngoi cng thc hin: ns, np, (n-1)d v (n-2)f (chng c gi l cc electron ha tr)Theo CHLT, nghin cu lin kt l qu trnh nghin cu s phn b mt electron trong trng ht nhn ca cc ht nhn ca cc nguyn t to ra phn t.Cc loi lin kt ch yu trong ho hc l lin kt cng ho tr v lin kt ion,ngoi ra cn c cc lin kt kim loi, v cc lin kt yu hn lin kt cng ho tr l lin kt Van der Valls, lin kt hydro


4.1.2 Mt s c trng ca lin ktCng thc tnh gn ng di lin kt (khi cc nguyn t c m in gn bng nhau): dA-B= rA + rBNu m in khc nhau nhiu th: dA-B = rA + rB- 0,09| A - B |

. 1. di lin kt: l khong cch gia hai ht nhn nguyn t lin kt vi nhau. V du Lin kt: H-FH-ClH-BrH-I d (A0) 0,92 1,28 1,42 1,62


di lin kt di lin kt ph thuc vo: Kiu lin kt, di lin kt gim khi bi lin kt tng ln.Nng lng lin kt:nu nng lng lin kt cao th di lin kt nh di lin kt ph thuc vo trng thi ho tr ca cc nguyn t, bn hp cht. di lin kt c th xc nh chnh xc bng thc nghim.nh cc phng php vt l hin i : nhiu x rngen, nhiu x electron, quang ph phn tCn tnh ton bng l thuyt th ch cho chnh xc tng i


mnh axit bn lin kt H-A (kJ/mol)


2 Gc ho trGc ho tr l gc to thnh bi 2 on thng ni ht nhn nguyn t trung tm vi 2 ht nhn nguyn t lin kt. Gc ho tr ph thuc vo bn cht nguyn t tng tc, kiu hp cht, cu hnh khng gian ca phn t.


Gc ho tr


BCl3 tam gicNH3 hnh chpT din, CH4ng thng- CO2


3. Bc lin ktBc lin kt l s lin kt to thnh gia 2 nguyn t tng tc trc tip vi nhaui vi lin kt cng ho tr th bc lin kt c xc nh bi s cp e tham gia lin kt gia hai nguyn tLin kt n c bc lin kt l 1, lin kt i c bc lin kt bng 2, lin kt ba c bc lin kt bng 3i vi cc h lin hp, bc lin kt khng phi l s nguyn m s thp phn V d trong benzen bc lin kt C-C l 1,5


4. Nng lng lin ktNng lng lin kt l nng lng thot ra khi to thnh lin kt v cng bng nng lng cn tiu tn ph hy lin kt c trong 1 mol phn t trng thi kh Lu : Nng lng lin kt v nng lng phn ly ca lin kt trng nhau khi phn t ch 2 nguyn t v d EH-H = EplH2 = 431 kj/mol Nhng i vi phn t nhiu nguyn t th nng lng lin kt c ly gi tr trung bnh, n khng trng vi nng lng phn ly tng lin kt mt trong phn t v d CH4


Nng lng lin kt ph thuc vo di lin kt, bi lin kt, bn lin kt


5. Momen lng cc ca lin kt c trng cho phn cc ca lin kt v phn cc ca phn t l i lng momen lng cc n v : DMomen lng cc l i lng vector chiu quy c t trng tm in tch dng qua in tch m


Momen lng cc


4.1.3 S lc v l thuyt lng t v lin kt ho hcv cu to phn tBn cht ho hc ca lin kt ho hc v cu trc phn t c gii quyt kh tt trn c s ca CHLTHin nay ngi ta cho rng phn t gm mt s gii hn cc ht nhn nguyn t v cc electron tng tc vi nhau v c phn b xc nh trong khng gian, to thnh mt cu trc bn vngC nhiu thuyt khc nhau gii thch bn cht ca lin kt ho hc, nhng thuyt c s dng rng ri nht l thuyt lin kt ho tr VB v thuyt MO .C s ca phng php l gii phng trnh sng Schrodinger i vi cc h phn t gm cc ht nhn v cc electron chuyn ng trong trng cc ht nhn


4.2 Lin kt ion4.2.1 Thuyt tnh in v lin kt ion ca Kossel (Kossel 1888-1967,ngi c). Nm 1916 Kossel cho rng phn t ca hp cht ho hc c to ra nh s chuyn electron ho tr t nguyn t ny sang nguyn t khc. Nguyn t mt electron ho tr bin thnh ion dng gi l cation v nguyn t nhn electron bin thnh ion m gi l anion. Cc ion ngc du ht nhau nn tin li gn nhau, nhng khi n qu gn nhau th s xut hin lc y ca cc lp v electron, khi lc ht v y cn bng nhau th cc ion dng li v to thnh phn t hp cht ion Nh vy lin kt ion l loi lin kt c to thnh nh lc ht tnh in gia cc ion tri du


V d+-NaCl


(Na) 11P 12NNa Na = 2,8,1Na mm v d phn ng, c 1 electron lp ngoi cng


(Cl) 18P 17NClo= 2,8,7Clo kh c c mu vng nht c 7 electron lp ngai cng


17P18N11P12NNaCl


Cl nhn electron t Na

17P18N11P12NNaCl


Lin kt ion

17P18N11P12NNa +2,8Cl-2,8,8


C Na v Cl c 8 electron lp v ngoi cng v to thnh hp cht NaCl

17P18N11P12NNa+2,8Cl-2,8,8Lc lin kt gia Nguyn t Na v Cl vi nhau


4.2.2 Kh nng to thnh lin kt ion ca cc nguyn tCc nguyn t c nng lng ion ho I cng nh kh nng to thnh cation cng d, in hnh cho kh nng ny l cc kim loi kim v kim thCc nguyn t c i lc i vi electron cng ln cng d to thnh cc anion, in hnh cho cc nguyn t ny l cc halogen, oxy, lu hunh.Nh vy lin kt ion d c to thnh gia nguyn t c tnh kim loi mnh v nguyn t c tnh phi kim mnh


S chnh lch m in ca cc nguyn t cng ln tnh ion ca hp cht cng cao. Mi quan h gia ion (%) v hiu s m in cc nguyn t theo Pauling

Lu : khng c lin kt ion thun tu, v ngay trong trng hp lin kt ion in hnh nh trong phn t NaCl tnh cht ion ch t c 94%. C l thuyt ln thc hnh khng nh mt electron gia cc ion khng bao gi bng khng.


4.2.3 Tnh cht ca lin kt ion. Ion c xem nh qa cu tch in c in trng phn b u mi hng trong khng gian dn n mt s c im ca lin kt ion nh sau: Tnh khng bo ha: th hin ch ion c th ht cc ion tri du vi lng khng xc nh. Tnh khng nh hng. N c th ht ion tri du theo bt k hng no. Cc tnh cht ny ca ion c nh hng n s phn b ion trong dung dch cng nh trong tinh th. Trong tinh th: cc ion c bao bc bi cc ion tri du vi lc lin kt hon ton nh nhau


4.2.4 S cc ha ionCc ion b phn cc mnh khi cc e lp ngoi lin kt yu vi ht nhnBn knh ion cng nh, in tch ion cng ln, cng in trng cng ln hiu ng gy cc ha cng cao.Bn knh ion cng ln, m my e cng linh ng th cng d b phn ccKhi nim Trong cc hp cht ion, ion ca lin kt khng bao gi t 100%, bi v cc ion ngc du khi n gn nhau th s phn cc (cc ho) ln nhau Do m my electron ca cation v anion khng tch ri nhau m che ph 1 phn S cc ha ca anion Cl- trong NaCl


2. Cc yu t nh hng n cc ha ion.Kh nng cc ha ca ion xy ra vi mc khc nhau tu thuc vo in tch, bn knh ion v cu hnh electron ca chng.Cc ion c cng cu hnh electron, in tch cng ln, kch thc cng b c kh nng cc ha cng mnh Li+ > Na+ > K+ >Rb+ > Cs+. Al3+ > Mg2+ > Na+Kh nng b cc ha ( b phn cc) ca ion ph thuc vo cu hnh electron, in tch v kch thc ca n. + Ion c cng in tch v cu hnh e th nu c kch thc cng ln th lc ht ca ht nhn vi electron ngoi cng cng yu nn chng d bin dng tc d b cc ha. Li+

+ Nu ion c in tch ging nhau v khch thc gn bng nhau th phn cc nh nht l cu hnh s2p6 v ln nht l s2p6d10 Trong hp cht ion, cation ng vai tr ion phn cc, cn anion ng vai tr ion b phn cc. V anion thng c kch thc ln, m my electron linh ng hn


3. nh hng ca s phn cc ion n tnh cht cc hp chtS cc ho ion mnh lm gim kh nng in ly thnh ion BaCl2 in ly mnh trong nc, HgCl2 hu nh khng in ly: Do cu hnh e ca Ba2+ (5s25p6) tc dng phn cc yu ion Cl-, cn ca Hg2+ (5s25p65d10 ) tc dng phn cc mnh ion Cl- bn: phn cc tng h gia cc ion trong mt hp cht lm tng cng ha tr, gim in tch hiu dng, gim lc ht ion gia chng nn bn tinh th gim phn ly, nng chy gim

Na+ v Cu+ c bn knh bng nhau, NaCl c t0nc= 8010C nhng CuCl c tonc = 4300C do Cu+ cc ho mnh hn Na+


tan: kh nng ho tan ca hp cht ion (mui) ph thuc vo 2 yu t l nng lng mng tinh th ion U v nng lng hydrat ho cation Eh. - Nu U > Eh nhiu th mui kh tan, ngc li th d tan - Nu khi U tng v Eh gim th tnh tan gim v ngc li th tnh tan tng, - Nng lng Eh ph thuc v kh nng phn cc nc ca cation, khi cation phan cc nc mnh th Eh tng. Th d


4.3 Lin kt cng ha tr4.3.1 Lin kt cng ho tr theo Lewis (1916)

Ni dung c bn: L loi lin kt c hnh thnh bng cch a ra electron ho tr ca mnh to thnh 1, 2, 3 cp electron chung gia 2 nguyn t Nh vy lin kt cng ho tr l loi lin kt bng cp eletron chung, cp electron chung c gi l cp electron lin kt Khi to thnh lin kt, cc nguyn t tham gia lin kt c 8 electron lp ngoi cng tng t nguyn t kh him Cc electron khng tham gia to thnh lin kt cng ho tr c gi l cc electron khng lin kt lin kt Khi hai nguyn t lin kt vi nhau bng 1 cp electron chung ta c lin kt n, 2 cp e chung l lin kt i, 3 cp e l lin kt 3 S lin kt gia 2 nguyn t gi l bc lin kt


Cng ho tr ca mt nguyn t c xc nh bng tng s lin kt cng ho tr ca nguyn t vi cc nguyn t khc trong phn tLu : Tu theo hp cht c th m lin kt cng ho tr c th l Lin kt cng ho tr khng c cc

Lin kt cng ho tr c cc

Lin kt cng ho tr cho nhn: l loi lin kt m cp e dng chung do mt nguyn t ng gp


++FF2s2p5P2s2p3PBiu din lin kt cng ha tr


++Qui tc bt tMi nguyn t khi tham gia lin kt c cu hnh electron lp ngoi cng c 8 electron ging vi kh him (ns2p6 )2


Lewis StructuresH2:Cl2:

Drawing Lewis StructuresCOCl224 vesHOCl14 ves

Cu trc LewisHF:H2O:NH3:CH4:H F

Double and Triple BondsNguyn t c th dng chung 4 electron to thnh lin kt i hoc 6 electron lin kt ba.O2:N2:

Quy tc bt t-cch tnh s electron lin ktS = N-AS tng s electron dng chung trong phn t.N l tng s electron cn thit lp ngoi cng ca tt c cc nguyn t trong phn t thu c cu hnh kh him (N =8, 2)A s electron c lp ngoi cng ca tt c nguyn t c mt trong phn t (chng ta phi iu chnh A khi nguyn t thay th bng ion) Thm electron i vi in tch m v tr electron khi in dng).


V di vi F2N = 2 x 8 : 16 e cnA = 2 x 7 (2 nguyn t F ) 14 e sn cS = N - A =16 -14 = 2 e dng chungi vi NH+4N = 1 x 8 ( 1 N ngt) + 4 x 2 (4 H ngt) = 16 eA = 1 x 5 (1 N ngt) + 4 x 1 (4 H ngt) - 1 (cho 1 in tch +) = 8 e sn cS = N - A = 16 8= 8 e dng chung


4.3.2 Lin kt cng ho tr theothuyt lin kt- ho tr (Valence bond-VB)


M u + V vic gii chnh xc phng trnh sng Schrodinger i vi h phn t khng th thc hin c,do ngi ta dng phng php gii gn ng, trong c hai phng php c s dng rng ri nht l phng php lin kt ho tr ca Heitler- London-Pauling-Slater (VB) v phng php ocbital phn t (MO) ca Mulliken- Hund-Lennard Jones+Phng php VB xut pht t lun im cho rng mt cp nguyn t trong phn t c lin kt vi nhau bng mt hoc mt vi cp electron dng chung, nghi l lin kt c nh ch gia hai nguyn t. V vy phng php ny cn c gi l phng php cp electron nh ch hay phng php hai electron- hai tm + Vic gii PT Schrodinger theo phng phpVB l tm hm sng phn t m t chuyn ng ng thi ca hai electron trong phn t v hm sng c xc nh mt cch gn ng bng tch cc hm sng nguyn t tng ng


1.Phn t Hydro theo Heitler-London Phn t H2 c to thnh t Ha v Hb v mi nguyn t H c 1 electron 1s.Electron 1 ca Ha c m t bng a(1) Electron 2 ca Hb c m t bng b(2) Nu b qua tng tc ca hai nguyn t, cc electron chuyn ng c lp i vi nhau th th hm sng ca c h l tch hai hm sng ring ca hai electronI = a(1). b(2) Thc t hai e c th hon i cho nhau m khng lm thay h do c hm gn ng khc hon ton tng ng II = a(2). b(1) T hp tuyn tnh ca hai hm trn l nghim gn ng m t trng thi ca h 2 e trong phn tH2 = C1a(1). b(2) + C2a(2).b(1) Gii pt ny, kt qu c 2 trng hp C1=C2 v C1 = -C2


s = Cs( a(1). b(2) + a(2).b(1) ) (l hm i xng) A = CA(a(1). b(2) - a(2).b(1)) (hm phn i xng)Theo nguyn l Pauli, ng vi hm i xng ng th hm spin phi phn i xng tc l 2 electron c spn tri du (), cn hm phn i xng th ng vi hm spin phi i xng, tc l 2 electron c spin cng du ()Bnh phng hm cho bit mt xc sut tm thy electron: Kt qu cho thy vi hm i xng c s tng mt electron khong gia hai ht nhn nguyn t, cn trng hp hm phn i xng c s gim mt xc sut electron khong gia ht nhn hai nguyn tS tnh ton v nng lng cho thy nu hai e c spin tri du th nng lng ca h gim khi hai nguyn t li gn nhau, cn khi hai e cng du th nng lng ca h tng ln khi hai e n gn nhauNh vy: Lin kt cng ho tr hnh thnh l do s kt i ca hai electron c spin tri du. Ta ni y c s xen ph ca hai orbital nguyn t


hm sng ca H2 theo Heitler-Londonzab12z1=z2


Phn t hidro theo Heitler -London


Nng lng theo VB ca phn t H2


2. Ni dung c bn ca thuyt lin kt ho tr (VB)a) Khi nim v lin kt cng ho tr Lin kt cng ho tr hnh thnh do s ghp i ca 2e c spin tri du v thuc v 2 nguyn t tham gia tng tc. V vy lin kt cng ho tr c gi l lin kt hai electron-hai tm v phng php VB c gi l phng php cp electron nh chLk cng ho tr c hnh thnh do xen ph gia 2 orbital nguyn t ho tr v thuc v 2 nguyn t tng tc Lin kt cng ho tr cng bn khi mc che ph ca cc orbital nguyn t cng ln Ch c xen ph dng mi to thnh lin kt, (du ca hm sng phi ging nhau) khi tch phn xen ph S = abd>0 Cn nu du hm sng khc nhau th s xen ph m, v c s y nhau ca cc ht nhn nguyn t, tch phn xen ph S < 0 , khng dn n s hnh thnh lin ktNgoi ra c s xen ph khng, tng ng S = 0, khi s xen ph khng to thnh lc ht hay lc y gia hai ht nhn nguyn t


Cc kiu xen ph : s to lin kt ,,Lin kt sigma ma: Hnh thnh do s xen ph trc, tc l s xen ph xy ra dc theo trc lin kt gia 2 nguyn t K hiu


Lin kt sigma


Lin kt Lin kt : Hnh thnh do xen ph bn, K hiu

xen ph bn p + p Phn t Etylen


Xen ph bn p-p to lin kt pi


Xen ph bn p-d v d-d to lin kt


Lin kt cng ho tr Khi hai AO d nm trong cc mt phng song song che ph nhau theo c 4 cnh hoaLin kt tng i t gp


S xen ph khng ( S=0)


S xen ph m


b) Kh nng to lin kt cng ho tr ca nguyn t v tnh bo ho ca lin kt cng ho tr Lin kt cng ho tr c th to thnh bi hai cch: cp e ghp i l gp chung hoc theo kiu cho- nhn Theo c ch gp chung: Cng ho tr ca mt nguyn t bng s e ho tr c thn ca nguyn t ( trng thi kch thch hoc c bn) Theo c ch cho nhn, th cp electron ghp i ca lin kt cng ho tr ch do 1 trong 2 nguyn t a ra, cn nguyn t kia nhn ly cp electron . Cp electron gi l cp electron ho tr t do. Ni cch khc l do s xen ph ca AO ho tr c 2 electron vi AO trng ca nguyn t kia V d NH3 + H+ NH4+Trong trng hp chung: Kh nng to thnh lin kt cng ho tr cc i ca mt nguyn t bng s AO ho tr ca nguyn t Kh nng to lin kt cng ho tr ca nguyn t hn ch nh vy nn ngi ta gi l tnh bo ho ca lin kt cng ho tr


c) Tnh nh hng ca lin kt cng ho trTnh c hng ca lin kt cng ho tr: Lin kt cng ho tr c hnh thnh theo nhng hng nht nh trong khng gian, phn t to thnh c hnh dng xc nhV d: SeH2 gc ho tr HSeH 90o Tuy nhin c nhiu hp cht nh H2O, NH3, , CH4gc ho tr khng bng 900 m chng c gc ho tr tng ng l 104,50 ; 107,30 v 109,50. iu ny ch c giit thch da v thuyt lai ho ca cc orbital nguyn t


d) Thuyt lai ho cc orbital nguyn t v cu hnh khng gian ca phn tCc nguyn t khi tham gia lin kt khng nhng s dng cc AO thun khit s, p,dm c th s dng cc AO trn ln trong nguyn t xen ph vi cc AO ca cc nguyn t khc, to thnh lin kt cng ho tr Khi t hp (trn ln) cc AO s, p, d ..to thnh nhng AO lai ho, th cc AO ny c nng lng, hnh dng, kch thc ging nhauC bao nhiu AO tham gia vo lai ho th c by nhiu AO lai ho to thnh v b tr i xng nhau trong khng gianiu kin cc AO c th lai ho l cc orbital c nng lng gn nhauCc kiu lai ho ph bin l sp3, sp2, sp, sp3d, sp3d2


Lai ho sp3 V d vi C-iu kin lai ha: ch xy ra khi 2 orbital c nng lng gn ging nhau


Lai ho sp31 orbital 2s + 3 orbitan 2p 4 orbital lai ho ng nht gi l trng thi lai ho sp3ngha l obital ny (23%) l bn cht s v (77 %) l bn cht p, Truc chnh ca 4 orbital lai ho sp3 phn b trong khng gian di cc gc bng nhau 109028 to nn hnh t din u.


Cc orbital lai ho sp3


Lai ho sp2Lai hoa sp2 c thc hien do s to hp 1 orbital s vi 2 orbital p tao thanh 3 orbital lai hoa sp2 phan bo oi xng di goc 1200. V du 1: Phan t BH3.B (Z = 5): 1s1 2s1 2p2Ket hp vi 3 ngt H 1s1


Hnh dng AO sp2Truc chnh ca 3 orbital lai ho sp2 nm trong mt mt phng v to vi nhau tng i mt mt gc 1200. Cn mt orbital khng lai ho ( thun khit) nm thng gc vi mt phng ca cc orbital lai ho


Cc orbital lai ho sp2


V d Phn t BF3


Phn t etylen


Lai hoa spLai hoa sp (lai hoa ng thang): s to hp 1 orbital s vi 1 orbital p (cua cung mot ngt) cho 2 orbital lai hoa sp phan bo oi xng co cung truc nam tren mot ng thang di goc 1800


Hnh dng AO lai ha spHai orbital lai ho sp cng nm trn mt trc thng, hai orbital 2p khng lai ho cn li nm trn hai mt phng thng gc vi nhau.


V d v hp cht c nguyn t trung tm lai ho sp.V du 1: phan t BeH2Be (Z = 4) 1s2 2s2 2p0Khi phan ng vi H, Be b kch thch co cau hnh 1s22s12p1Luc nay trong nguyen t Be xy ra s lai hoa gia orbital 2s va 2p e tao 2 orbital lai hoa sp.


V du 2: Phan t BeCl2.Be (Z = 4): 2s1 2p1Cla (Z = 17): 3s2 3p5Clb 3s2 3p5


Phn t axetylen


Lai ho sp3dL s t hp ca cc AO: s, px, py ,pz v dZ2 to thnh 5AO lai ho c trc hng v 5 nh ca mt lng chp tam gicV d phn t PCl5, PF5


Lai ho sp3d2L s t hp ca 1 AO s, 3 AO p v 2AO d to thnh 6 AO lai ho sp3d2= hng v 6 nh ca mt hnh bt dinTh d SCl6, , SF6 ,SiF6


D on trng thi lai ho ca nguyn t trung tmDa vo gc ho tr- Nu gc ho tr 109028 l lai ho sp3 ,- Nu khi gc ho tr 1200 l sp2Da vo tng T ca s lin kt v s cp e t do nguyn t trung tm ( T= s lk + s cp e t do)+ T = 2 lai ho sp+ T = 3 lai ho sp2+ T = 4 lai ho sp3+ T = 5 lai ho sp3d+ T = 6 lai ho sp3d2


Mi quan h gia lin kt , s cp e ho tr t do v trng thi lai ho ca nguyn t trung tmS lin kt bng s nguyn t lin kt vi nguyn t trung tm tnh cp e t do ca nguyn t trung tm:+ Tnh tng s e ho tr X ca cc nguyn t trong phn t Nu phn t c in tch +a th s e l X-a Nu thn t c in tch b th s e l X+ b+ Tnh s e bo ho dnh cho cc nguyn t bin lin kt vi nguyn t trung tm (Y): tnh i vi H l 2, cc nguyn t khc l 8+ S cp e t do = (X-Y): 2


V d


Hnh dng phn t v gc lin kt


M hnh s y nhau ca cp electron lp ho tr (VSEPR) ca GillespieQuy tc:Cc cp electron lp ha tr phi c phn b cch xa nhau nht c c lc y nh nht gia chngC s khng tng ng gia cp electron lin kt v khng lin kt, cp e khng lin kt chim khong khng ln hn Lc y ca cc cp e gim dn theo th t sau: Cp e ho tr t do- cp e ho tr t do > Cp e ho tr t do - cp e lin kt > Cp e lin kt - cp e lin ktHnh dng electronHnh dng phn t


CH4CH4: 4 cp e u lin kt v hng v 4 nh ca t din; gc ho tr l 109028


NH3NH3: trong 4 cp e c mt cp t do; lc y ca n lm cc cp e lin kt xch li gn nhau; gc ho tr ca H-N-H l 107,30


H2OH2O: lp v e ho tr ca O cha 2 cp ho tr t do dn n cc lin kt O-H xch li gn nhau hn, t gc lin kt ca H-O-H l 104,50


So snh gc ho tr ca CH4, NH3 v H2O


nh hng electron khng lin kt ln gc lkGc lin kt H-X-H gim t C n N n O:


nh hng ca lin kt bi ln gc lin ktelectron trong lin kt bi y xa hn vi electron lin kt n.


e) Bac lien ket cua lien ket cng ho trCac lk cong hoa tr co the la lk n (bac 1), lk oi (bac 2), lk ba (bac 3) e noi len ac iem nay ta dung khai niem bac lien ketBc ca lin kt c xc nh bi s cp e tham gia lin kt gia 2 nguyn t

.


V dPhn t N2

Bc lin kt = (s e tham gia lin kt/2) = (2x3)/ 2 = 3Phn t CO2Bc lin kt = (tng s e tham gia lin kt/ 2x2 lin kt) = 2x4 /4 =2


Phn t BCl3

Bc lin kt = 8/2x3 = 1,33


Chemistry 140 Fall 2002Thermochemistry branch of chemistry concerned with heat effects accompanying chemical reactions.Direct and indirect measurement of heat.Answer practical questions: why is natural gas a better fuel than coal, and why do fats have higher energy value than carbohydrates and protiens.Chemistry 140 Fall 2002

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BAI4lien Ket Hoa Hocppt