1. UNIT CELL – The smallest repeating unit of a crystalline solid EXP11-1 (of 11) UNIT CELLS

2. SIMPLE CUBIC UNIT CELL Length of 1 side of the unit cell: Full atoms in the unit cell: 2r (r = radius of one particle) 8 × ⅛ = 1 EXP11-2 (of 11)

3. BODY-CENTERED CUBIC UNIT CELL Length of 1 side of the unit cell: Full atoms in the unit cell: 4r ___ √3 (8 × ⅛) + 1 = 2 s 2 + d 2 = (4r) 2 s 2 + s 2 + s 2 = (4r) 2 3s 2 = 16r 2 s 2 = 16r 2 _____ 3 = 4r√3 ______ 3 d s s s 4r EXP11-3 (of 11)

4. The most efficient ways to pack atoms: 1 st layer EXP11-4 (of 11)

5. The most efficient ways to pack atoms: 1 st layer 2 nd layer EXP11-5 (of 11)

6. The most efficient ways to pack atoms: 2 nd layer 1 st layer 3 rd layer This is hexagonal closest packing (hcp), and it makes hexagonal prism unit cells EXP11-6 (of 11)

7. The most efficient ways to pack atoms: 2 nd layer 1 st layer 3 rd layer EXP11-7 (of 11)

8. The most efficient ways to pack atoms: 2 nd layer 1 st layer 3 rd layer This is cubic closest packing (ccp), and it makes face-centered cubic unit cells EXP11-8 (of 11)

9. FACE-CENTERED CUBIC UNIT CELL EXP11-9 (of 11)

10. UNIT CELLS FOR IONIC CRYSTALS Zinc sulfide Zn= S=S= (8 x 1 / 8 ) (4 x 1) + (6 x 1 / 2 )= 4  ZnS EXP11-10 (of 11)

11. UNIT CELLS FOR IONIC CRYSTALS Sodium chloride Na = Cl = (12 x 1 / 4 ) (8 x 1 / 8 ) + (1 x 1) + (6 x 1 / 2 ) = 4  NaCl EXP11-11 (of 11)