Chemistry 17 Friday, October 06, 2006

Chemistry 17 Friday, October 06, 2006 - Friday, October 06,...

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Friday, October 06, 2006 Chemistry EXAM #2 Text Sections 4.7 - 7.6 SOLID FOUNDATION How do atoms arrange in the solid state? What type of bonding exists in solid metals? TEXT: Sections 8.0 – 8.6 CUBIC UNIT CELLS 1. Crystal lattice a. 3-d array of atoms b. Long-range repeating pattern 2. Look at unit cell a. smallest repeating pattern in 3-d 3. Three types of cubic unit cells(Figure 8.3) a. Simple cubic (SC) b. Body- centered cubic (BCC) c. Face-centered cubic (FCC) 4. other example a. hexagonal arrangement DIFFERENCES BETWEEN CELLS 1. Unit cell defined by nuclei at the corners 2. Unit cell stoichiometry a. #of atoms (or fractions) inside cell b. Corner atoms:1/8 inside i. SC: (8 x 1/8) = 1 1. CN = 6 a. PE = 52% c. Body atoms: all inside i. BCC: (8 x 1/8) + (1x1) = 2 1. CN = 8 a. PE = 68% d. Face atoms: ½ inside i. FCC: (8 x 1/8) + (6x ½) = 4 1. CN = 12 a. PE = 74% 3. Coordination number (CN) a. # of other atoms that an atom touches (see bullet #2) 4. Packing Efficiency(PE) a. How much volume is taken up by atoms? (not “void space”)
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This note was uploaded on 03/20/2008 for the course CH 101 taught by Professor Bigham during the Fall '08 term at N.C. State.

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Chemistry 17 Friday, October 06, 2006 - Friday, October 06,...

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