tailieunhanh - Giáo án điện tử môn Hóa Học: Tinh thể

Định đề Hammond-Leffler cho rằng cấu trúc của các phân tử tại trạng thái chuyển tiếp trong các phản ứng hóa học sẽ tương tự với sản phẩm hay hóa chất khởi đầu có năng lượng bên trong gần giống nhất. | Solids crystalline amorphous well defined structures no orderly structure glass quartz SiO2 crystal lattice system of points describes arrangement of particles unit cell repeating structural unit lattice 7 unit cells simple cubic formed from packing spheres unit cells crystalline solids hexagonal closest packing “abab” layers “abca” layers cubic packing “aaa” layers in 3 dimensions hexagonal closest pack cubic closest pack “abab” layers simple cubic body centered cubic Three-Dimensional Cubic Lattices Simple cubic Face-centered cubic Body-centered cubic 1/8 x 8 = 1 particle (1/8 ) x 8 + 1 = 2 particles (1/8 ) x 8 (1/2 ) x 6 + = 4 particles cubic closest pack a a a a b a b a b c a b c coordination number = 6 coordination number = 8 coordination number = 12 Calculation of atomic radii Cu faced-centered cubic density = g/cm3 mass = g/mol g mol 1 mol x 1023 atoms 4 atoms unit cell g cm3 x 10-23 cm3 / unit cell ( ) 1/3 = x 10-8 cm ( x 10-8)2 + ( x 10-8)2 = (4r)2 r = x 10-8 cm 1 cm 1 x 10-2 m 1 x 10-12 m 1 pm = 127 pm r+2r+r lattice parameter, a X-Ray Diffraction by Crystals Bragg Equation n = 2d sin diffraction interference between waves caused by object in their path constructive or destructive d Types of Crystalline Solids Covalent Ionic Molecular atoms in lattice ions in lattice molecules in lattice . depends on bonding forces Cdiamond 3550oC NaCl 800OC H2O 0oC covalent ionic H-bonding Covalent solids atoms in lattice carbon sp3 sp2 sp2 hardest material known conduct electricity - e- diamond doesn’t conduct electricity graphite buckminsterfullerene Covalent solids atoms in lattice metals every lattice point - atom of 1 metal body-centered cubic face-centered cubic hexagonal close packed brass substitutional alloy steel interstitial alloy share valence e- e- “sea” melting point Na 97oC Cr 1890oC good conductors Ionic Solids trigonal hole tetrahedral hole octahedral hole too small r = R r = | Solids crystalline amorphous well defined structures no orderly structure glass quartz SiO2 crystal lattice system of points describes arrangement of particles unit cell repeating structural unit lattice 7 unit cells simple cubic formed from packing spheres unit cells crystalline solids hexagonal closest packing “abab” layers “abca” layers cubic packing “aaa” layers in 3 dimensions hexagonal closest pack cubic closest pack “abab” layers simple cubic body centered cubic Three-Dimensional Cubic Lattices Simple cubic Face-centered cubic Body-centered cubic 1/8 x 8 = 1 particle (1/8 ) x 8 + 1 = 2 particles (1/8 ) x 8 (1/2 ) x 6 + = 4 particles cubic closest pack a a a a b a b a b c a b c coordination number = 6 coordination number = 8 coordination number = 12 Calculation of atomic radii Cu faced-centered cubic density = g/cm3 mass = g/mol g mol 1 mol x 1023 atoms 4 atoms unit cell g cm3 x 10-23 cm3 / unit cell ( ) 1/3 = x 10-8 cm ( x 10-8)2 +