1. Solids crystalline amorphous well defined structures no orderly structure glass quartz SiO 2 crystal latticesystem of points describes arrangement of particles

2. unit cell repeating structural unitlattice 7 unit cells simple cubic formed from packing spheres

3. unit cells crystalline solids hexagonal closest packing “abab” layers “abca” layers cubic packing “aaa” layers in 3 dimensions hexagonal closest packcubic closest pack “abab” layers simple cubic body centered cubic

4. Three-Dimensional Cubic Lattices Simple cubic Face-centered cubic Body-centered cubic 1/8x 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 c coordination number =6 8 12

5. Calculation of atomic radii Cufaced-centered cubic density = 8.92 g/cm 3 mass = 63.546 g/mol 63.546 g mol 1 mol 6.022 x 10 23 atoms 4 atoms unit cell8.92 g cm 3 4.732 x 10 -23 cm 3 / unit cell( ) 1/3 = 3.617 x 10 -8 cm (3.617 x 10 -8 ) 2 +(3.617 x 10 -8 ) 2 = (4r) 2 r = 1.279 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

6. X-Ray Diffraction by Crystals Bragg Equation n = 2d sin  diffractioninterference between waves caused by object in their path constructive or destructive  d

7. Types of Crystalline Solids CovalentIonicMolecular atoms in lattice ions in lattice molecules in lattice m.p.m.p. depends on bonding forces C diamond 3550 o CNaCl800 O C H2OH2O0oC0oC covalent ionic H-bonding

8. Covalent solids atoms in lattice carbon sp 3 sp 2 hardest material known conduct electricity -  e - diamond doesn’t conduct electricity graphitebuckminsterfullerene

9. Covalent solids atoms in lattice metalsevery 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 Na97 o C Cr1890 o C good conductors

10. Ionic Solids trigonal holetetrahedral holeoctahedral hole too small r = 0.225 Rr = 0.414 R composed of charged species – anions and cations each unit cell - anions at lattice pointscations in “holes” NaCl face-centered cubic CsClsimple cubic unit cell neutral stoichiometry of compound different in size

12. Molecular Solids molecules in lattice hemoglobin reaction center 1988 1962 Perutz and KendrewDeisenhofer, Huber and Michel