化學(xué)競賽雜化軌道理論(存儲版)
【正文】 While it is longer in the case sp3d （ dsp3 雜化 軸向鍵長較短， sp3d雜化則較長 PF5 3s 3p P P* 3d P* (sp3d) 3d We need hybrid orbitals suitable for bonds to 5 atoms. ns and np binations can only provide four, so we need to use nd orbitals (if they are available). 3dz2 3pz 3py 3px 3s sp3dz2 The appropriate mixture to form a trigonal bipyramidal arrangement of hybrids involves all the ns and np orbitals as well as the ndz2 orbital. yzx12345Valence bond theory treatment of a trigonal bipyramidal molecule: the bonding in PF5 F 2s 2p F 2s 2p F 2s 2p 3d P* (sp3d) F 2s 2p F 2s 2p The overlap of the sp3d hybrid orbitals on P with the 2p orbitals on the F atoms gives five PF (sp3d)2p ? bonds in two sets: the two axial bonds along the zaxis (180176。 Structure of ABn Molecules 2. AB3 i. Trigonal Pyramidal type (8, or 26 valence electron) ex. NH3 , PF3, PCl3, AsCl3 sp3 hybridization ii. Trigonal planar type (6, 24 valence electron) Centric atom B: sp2 hybridization 64?)4()3()2()1( 4321 ClClClB cccc ????? ? ???? 24 6 18 12 6 BC l C lC lIsoelectron analogy: AlF3, NO3, CO32, SO3, Cl2CO, (H2N)2C=O, Cl2C=S :e le c t r o ns ?antibonding nonbonding bonding For four atom angular type moleculars, forming one bonding, two nonbonding and one antibonding orbitals, in general Example: BH3 ex. BF3, NO3, CO32, SO3 sp2 FBFF?3 sp2 hybrid orbitals each with one electron. ?This one electron pairs with the hydrogen electron. ii. Trigonal planar type (6, 24 valence electron) 646432324 :e l e c t rons ?????ex. ClF3, BrF3, sp3d hybrid orbitals iii. T type (28 valence electron) 167。 , triangular, f=， ?=1/3 ?h1 ?h2 ?h3 x y A trigonal planar molecule and sp2 hybridization: the bonding in BH3 2s 2p B B* B HHHxy1 2 0BH3 sp2 hybrid p orbital 1s 1s 1s 3 H B* sp2 2p ?h1 ?h2 ?h4 ?h3 z z)( x , y , a l o n g 2 ][21zyxh ppps ?????z)y,( x , a l o n g 1 ][21zyxh ppps ?????( x , y , z ) a l o n g ][214h zyx ppps ?????y , z )( x , a l o n g 3 ][21zyxh ppps ?????? One s and 3 p AO’s mix to form a set of four hybrid sp3 orbitals. c. sp3 hybrides (tetrahedral)
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