LIEN KET HOA HOC
3.10. Khi cdc nguyen tft tiln lai gdn nhau xud't hien luc hiit va luc day Luc hiit
dugc thuc hien gifta cdc dien tfch trai dau : cac electron tren cac obitan va cac hat nhdn. Lgc ddy la luc tac dung gifia cac dien tfch cung dau : cac hat nhdn ddy nhau, cac electron tren cac obitan day nhau. Khi luc hiit cdn bang vdi lgc ddy lien kit dugc tao thanh.
3.11. D.
3.12. Mdi nguyen tft flo cd 1 electron ddc thdn tren obitan 2p. Khi hai nguyen tft flo kdt hgp vdi nhau, mdi nguyen tft se gdp chung mdt electron ddc thdn tao ra mdt cap electron chung cfta ca hai nguydn tft trong phdn tft F2. Cap electron nay uu tien tdn tai d vung gifia hai hat nhdn va tao ra 1 lien kdt cdng hod tri.
Cd thi bilu diln lien kit va cd'u tao electron trong phdn tft flo nhu sau : :F: F : (cdng thftc electron) hay F - F (cdng thftc cd'u tao).
3.13. Nguyen tft brom cd cdu hinh electron ldp ngodi cung la : [Ar] 3d 4s 4p trong dd cd 1 electron ddc thdn tren mdt obitan 4p. Khi tham gia lien kit vdi nguyen tft H dl tao thanh phdn tft HBr, nguyen tft H ddng gdp 1 electron ddc thdn tren obitan Is, nguyen tft brom ddng gdp 1 electron ddc thdn tren obitan 4p, lien kit dugc tao thanh do sg dung chung mdt cap electron. Do hai nguydn tft khdc nhau vl dd dm dien nen cap electron bi hftt lech vl phia nguyen tft brom. Nhu vdy, ngudi ta ndi rdng lien kit gifta H va Br la lien kdt cdng hod tri phdn cgc va duge bilu diln bdng cdng thftc H: Br : ' 3.14. Mdi nguyen tft nita diu cd 5 electron tren ldp ngoai cung trong dd cd
3 electron ddc thdn d tren 3 obitan 2p. Khi hai nguydn tft nita kit hgp thdnh phdn tft N2, chung cung sft dung chung 3 electron ddc thdn dl tao ra 3 lien kit. Nhu vdy, mdi nguyen tft nita trong N2 diu cd dugc 5 + 3 = 8 electron d ldp electron ngoai cung : I N = N I. Nguyen tft nita trong N2 thoa man dugc quy tdc bat tft.
Trong phdn tft NO cd 1 lien kit ddi do sg dung chung 2 electron ddc thdn (trong ba electron ddc thdn) cua mdt nguyen tft nita va hai electron ddc thdn cfta nguyen tft oxi. Nhu vdy chi cd nguyen tft oxi cd dft 8 electron (6 + 2 = 8) la thoa man quy tdc bat tft, cdn nguyen tft nita chi cd 7 electron (5 + 2 = 7) khdng thoa man dugc quy tdc bat tft : • N = O : 3.15. Lien kit cdng hod tri dugc tao thanh do su dung chung cdc' cap electron
cua 2 nguyen tft thudc 2 nguyen td khac nhau (cd dd dm dien khdc nhau) dugc ggi la lien kdt cdng hod tri phdn cgc.
Thf du dan gian nhd't vl lidn kdt cdng hod tri phdn cgc la lien kit trong phdn tft HF. Nguyen tft H ft dm dien ban nguyen tft F, do dd cap electron lien kdt chung se bi hut lech vl phfa nguyen tft F. Phdn tft HF la mdt ludng cue dien vdi ddu dm la nguyen tft F va ddu duong eua ludng cgc la nguyen tft H. Trong cac phdn tft nhilu nguyen tft nhu NH3, H2O, H2S, SO2... diu cd cdc lien kit cdng hod tri phdn cue do cac nguyen tft H va N, O va H, S va H, S va O... ed dd dm dien khac nhau.
3.16. Lien kdt cho - nhdn la lien kit CHT phdn cue do hai nguyen tft dung chung mdt cap electron thudc vl mdt nguyen tft trudc khi tham gia tao lien ket. ,
Xet phdn tft NO2 : Trong phdn tft NO (xem bai 3.14), nguyen tft oxi cd du 8 electron d ldp ngoai cung va thoa man quy tdc bdt tft. Nguyen tft nito mdi ed 7 electron. Trong phdn tft NO2 cung nhu vdy, nguyen tft nita chi cdn 1 electron ddc thdn khdng dft dl ghep ddi vdi hai electron ddc than cua mdt nguyen tft oxi thft hai. Lien kit cdng hod tri gifta nguyen tft nito va nguyen tft oxi thft hai se dugc thuc hien bdng sg cho - nhdn cap electron cfta nguyen tft nita. Nhu vdy nguyen tft oxi thft hai cung cd 8 electron. Nguyen tft nito vdn chi cd 7 electron. Nhu vdy, trong phdn tft NO2 cd 3 lien kit cdng hod tri. Cdng thftc cd'u tao cua NO2 :
O N <
O
B a l i s
SU LAI HOA CAC OBITAN NGUYEN TQ. SU HINH T H A N H LIEN KET DON,
LIEN KET DOI VA LIEN KET BA
3.17. Su lai hod gifta cdc obitan 2s va 3 obitan 2p cua nguyen tft C tao ra 4 obitan lai hod (sp^) gid'ng bet nhau hudng vl 4 dinh cua mdt tft dien diu. Tren mdi obitan lai hod nay cd 1 electron ddc thdn se ghep ddi vdi mdt electron ddc thdn cua mdt nguyen tft hidro. Bdn lien kit cdng hod tri dugc hinh thdnh. Gdc lien ket la gdc tft dien nen cd gid tri bdng 109°28'.