Chng II

LIEN KET TRONG TINH THE CHAT RAN

I. CAC LOAI LIEN KET TRONG TINH THECac nguyen t khi tien lai gan nhau e tao thanh tinh the Co s tng tac gia chung Nang lng cua toan he giam. o giam nang lng nay xac nh nang lng lien ket cua tinh the.Nang lng lien ket khac nhau gia cac loai tinh the:Tinh the kh tr:Elien ket = 0.02 0.2 eV/nguyen tTinh the kim loai kiem: Elien ket = 1 eV/nguyen tTinh the nhom 4 nh Ge, Si:Elien ket = 4 ; 5 7,36 eV/nguyen t

1. BAN CHAT CUA CAC LC TNG TAC TRONG TINH THE Khi cac nguyen t lai gan nhau, gia cac nguyen t co the co cac tng tac:+ Tng tac hap dan.+ Tng tac t.+ Tng tac tnh ien.Neu hp cac tng tac o lam nang lng he giam lc hut gia cac nguyen t se thang tinh the on nh.Neu hp cac tng tac o lam nang lng he tang lc ay thang tinh the khong hnh thanh.

Nh vay:Uien >> Ut >> Uhap danVay nguon goc lien ket chnh trong tinh the la tng tac tnh ien.+ Vi nguyen t nang nhat co A = 250 nang lng hap dan vao khoang: Uhp dn ~ 2,4.10-32 eV+Vi cac nguyen t co momen t c ban bang magnetron Born nang lng tng tac: Ut ~ - 7.10-6 eV

Tng tac ay gia cac ien tch cung dau: hat nhan hat nhan; electron electronTrong o: A, n = hang so, n >> 1; r : khoang cach gia hai nguyen t.TNG TAC TNH IENTng tac tnh ien trong tinh the gom:Tng tac hut va tng tac ay Tng tac hut gia cac ien tch trai dau: electron hat nhan

Vay: Nang lng tng tac gia hai nguyen t gom:U(r) = Uhut + UayKhi r = ro , U(ro) = Umin ro = khoang cach thc gia hai nguyen t gan nhau nhat trong tinh the.Khi r 0 : Uay >> Uhut U(r) Khi r : Uay

Tuy theo so electron hoa tr cua cac nguyen t ma chung co the phan bo lai electron bang cach: nhng, hay thu, hay gop chung cac electron hay ch bien dang cac lp vo e-. 2. CAC LOAI LIEN KET TRONG CHAT RANS khac biet gia cac loai lien ket trong chat ran la do s phan bo cua cac ien t hoa tr cua cac nguyen t. Khi a cac nguyen t lai gan nhau e tao tinh the chat ran, chung co s phan bo lai cac ien t trong cac nguyen t. Qua trnh nay thoa ieu kien:+ Bao toan ien tch cua he. + Xu hng sao cho cac nguyen t co lp vo ngoai cung ay e-.

CAC LOAI LIEN KET C BAN TRONG TINH THE1-Lien ket Van der Waals Lien ket yeu gia cac nguyen t trung hoa bi tng tac Van der Waals London do s thang giang trong phan bo ien tch cua cac nguyen t.2-Lien ket ion Cac nguyen t trao oi ien t hoa tr vi nhau e tao thanh cac ion (+) va ion (-) lien ket bang lc hut tnh ien cua cac ion trai dau.3-Lien ket ong hoa tr Lien ket gia cac nguyen t bang cach gop chung cac electron hoa tr Cac nguyen t trung hoa co s phan bo electron chum len nhau mot phan.4-Lien ket kim loai Cac electron hoa tr c giai phong khoi nguyen t va co the di chuyen t do trong tinh the. Cac ion (+) c nam v tr nut mang.

II. V DU MINH HOA CHO CAC LOAI LIEN KET TRONG CHAT RAN1. TINH THE KH TR A. IEN HNHCac tinh the kh tr nh He, Ne, Ar co lp vo ien t hoa tr hoan toan ay, nang lng ion hoa rat ln, nang lng lien ket gia cac nguyen t rat yeu, khong u lam bien dang cac lp vo electron cua chung tng tac chu yeu Van der Waals London

Xet hai nguyen t 1 va 2 cach nhau mot khoang r nh hnh.

Momen lng cc ien cam ng tai nguyen t 2 la P2:Trong o = o phan cc ienNguyen t cang gan nhau lien ket cang manh Tng tac Van der Waals Lon don ong vai tro chnh trong cac lien ket cua cac tinh the kh tr.

Khi a cac nguyen t lai gan nhau hn co them tng tac ay co dang:Trong o: C 46 ; A 412 la cac hang so dng

Vay: Tng tac Van der Waals London ong vai tro chnh trong lien ket cua cac tinh the kh tr.

B. MOT SO TNH CHAT CUA TINH THE KH TRLien ket cua tinh the kh tr la lien ket Van der Waals tng tac hut xu hng cac nguyen t keo ve mnh so cac nguyen t lan can toi a. Tinh the co cau truc xep chat: lap phng tam mat cho a so tinh the kh tr, va luc giac xep chat vi tinh the He.Cac tinh the kh tr la chat ien moi trong suot co nang lng lien ket nho va nhiet o nong chay thap, de nen.

Nang lng lien ket cua cac tinh the kh tr Gia s tinh the kh tr la mot tap hp cac nguyen t nam tai nut mang, bo qua ong nang cua chung Nang lng tng tac cua nguyen t nam tai goc toa o vi cac nguyen t con lai i trong tinh the la the nang: ri R : khoang cach gia hai nut lan can gan nhat. Nang lng tng tac tnh tren mot nguyen t la:

Mat khac, theo the Lennard _ Jones ta co:at ri = iR

An phu thuoc Loai mang tinh the va n.Khi n : An so lan can gan nhat. VD: mang lap phng tam mat An = 12.Khi n giam An tang v co s ong gop cua cac nguyen t xa hn.

Khoang cach can bang Ro gia cac lan can gan nhat c tnh t ieu kien:Ket qua l thuyet nay phu hp tot vi ket qua thc nghiem oi vi cac nguyen t co khoi lng ln, con oi vi cac nguyen t co khoi lng nho th co s sai khac ang ke. Nguyen nhan la do bo qua ong nang cua cac nguyen t.

Nang lng lien ket can bangKet qua nay cung phu hp vi ket qua thc nghiem oi vi cac nguyen t co khoi lng ln. Khi khoi lng giam co s sai lech nhieu vi ket qua thc nghiem. Nguyen nhan la do bo qua ong nang cua cac nguyen t.

o cng cua tinh the Bo cng B cua tinh the la so o cua nang lng can e lam bien dang tinh the. Tinh the co B cang ln th cang cng. Nghch ao cua B la o nen cua tinh the.Vi: V la the tch cua tinh the; P la ap suat.

khoang cach can bang, nang lng la cc tieu nen ta co:

2. TINH THE ION A. IEN HNHLa cac Halogen kiem: NaCl, LiF, CsCl, Cac nguyen t kim loai kiem co mot electron hoa tr (VD: Na), con cac nguyen t Halogen co 7 electron hoa tr (VD: Cl).+ Nguyen t Na nhng 1 electron hoa tr ion Na+ co 8 electron lp vo ngoai cung.+ Nguyen t Cl nhan 1 electron hoa tr ion Cl- co 8 electron lp vo ngoai cung. Lien ket ion

B. TNH CHAT Tng tac gia NaCl la tng tac hut tnh ien gia cac ion trai dau.Lien ket manh, khong co electron t do. Cac tinh the lien ket ion khong dan ien nhiet o thap, nhiet o cao o dan ien tang. Co iem nong chay cao, o cng ln, hap thu hong ngoai.

NANG LNG LIEN KET NANG LNG MANG UMe n gian , ta dung mo hnh cau truc cua 1 tinh the ion hoa tr I : NaClUM la nang lng can chi e tach tat ca cac hat trong mang ra xa vo han. UM la 1 ai lng ac trng trong tinh the lien quan ti cac tnh chat cua tinh the: o nen, o gian n nhiet, nhiet o nong chay, o ben c hoc

THE TAC DUNG CUA CHUOI MANG LEN HAT X

the nang tac dung cua ca chuoi len x bang 2 lan the nang tac dung cua na chuoi len x.The tac dung cua na chuoi mang len hat x

THE TAC DUNG CUA MAT MANG LEN XThe tac dung cua na mat mang len x: The tac dung cua ca mat mang len x bang 2 lan the tac dung cua na mat mang len x.

THE TAC CUA MANG KHONG GIAN LEN XThe tac cua na mang khong gian len x: The tac dung cua ca mang khong gian len x bang 2 lan the tac dung cua na mang len x.Do o, the cua toan mang tinh the tac dung len x: = 2(1 + 2 + 3)

Nang lng mang khi mang co NA hat la:at: M = 2(1 + 2 + 3 ) = hang so MadelungM la mot tha so hnh hoc, cac vat chat khac nhau, nhng co cung cau truc th co M giong nhau.

Nang lng lien ket tren mot ion: + Nang lng mang cua 1 hp chat ion vi hoa tr ion bat ky Z1, Z2 la: Nang lng lien ket tren mot ion:

Tng t, ta co the tnh c o cng cua tinh the ion:O CNG CUA TINH THE ION Vi = const co th nguyen la n v chieu dai.

3.TINH THE ONG HOA TR A. IEN HNHCac nguyen to thuoc nhom IV trong bang phan loai tuan hoan nh Ge, Si, C Moi nguyen t nay co 4 electron hoa tr, khi lien ket vi nhau chung gop 4 electron hoa tr vi 4 nguyen t lan can tao thanh 4 lien ket ong hoa tr moi lien ket co 2 electron hoa tr. LIEN KET ONG HOA TRQuanh mot nguyen t bat k co 4 nguyen t lan can nam tai nh cua hnh t dien ma nguyen t ang xet nam tam cua t dien o kieu mang kim cng.

B. TNH CHATLien ket ong hoa tr manh. Elk khoang bang nang lng lien ket cua lien ket ion.ac iem noi bat cua lien ket ong hoa tr la tnh nh hng cua tinh the.Co nhiet o nong chay cao, o ran va o ben cao, o deo thap, o dan ien thap nhiet o thap.

4. TINH THE KIM LOAI A. IEN HNHLa cac nguyen to nhom 1 trong bang phan loai tuan hoan. VD: K, Li, Na Moi nguyen t ch co 1 electron hoa tr lien ket yeu vi ion. Khi cac nguyen t lai gan nhau tao thanh tinh the, electron hoa tr thoat khoi nguyen t (v ham song phu nhau) tr thanh cac electron t do trong toan mang tinh the Cac electron dan. LIEN KET KIM LOAI

B. TNH CHATCo tnh dan ien tot.Nang lng lien ket nho so vi nang lng lien ket ion. Khoang cach gia cac nguyen t tng oi ln cac ion nut mang co the dch chuyen tng oi xa ma khong b pha v lien ket o deo cao, de uon, dat, keo si.Kim loai nang co lien ket chac chan nhiet o nong chay cao, o ben c hoc ln.Cau truc: cac nguyen t co xu hng keo ve mnh toi a cac nguyen t khac hnh thanh cau truc xep chat: lap phng tam mat

V DU Cu lap phng tam mat Mg luc giac xep chat. Mn lap phng tam khoi