Chap13_Part1

Chap13_Part1 - Covalent-Network Solids These materials are held together by networks of covalent bonds(e.g quartz or SiO2 They are very hard and

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Covalent-Network Solids These materials are held together by networks of covalent bonds (e.g., quartz or SiO 2 ). They are very hard and have very high melting points (1000’s o C). Diamond is an array of carbon atoms bonded to other carbon atoms by single C-C bonds. Graphite is also a carbon-based solid but has a different structure. The atoms are arranged in hexagonal layers where each atom bonds to three others in the layer. The planes of bonded hexagons are held together by noncovalent dispersion forces. 2
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Ionic Solids These materials are held together by ionic (i.e., electrostatic) interactions. The material strengths vary greatly with the charges on the interacting ions: Na(+)Cl(-) melts at 801 o C & Mg(2+)O(2-) melts at 2852 o C. There are several basic types of crystal structures found in ionic solids. 3
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Ionic Solids: (1) NaCl Crystal Structure Cl - Na + type: face-centered cubic coordination # for Na + : 6 Cl - coordination # for Cl - : 6 Na + Other compounds with this crystal structure: LiF, KCl, AgCl, CaO 4
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Ionic Solids: (2) CsCl Crystal Structure type: body-centered cubic coordination # for Cs + : 8 Cl - coordination # for Cl - : 8 Cs + other compounds with this structure: CsBr, AlCo, BeCu, MgCe or Cs + Cl - Cs + Cl - 5
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Ionic Solids: (3) ZnS Crystal Structure type: face-centered cubic coordination # for Zn 2+ : 4 S 2- coordination # for S 2- : 4 Zn 2+ other compounds with this structure: AgI, BeS, CuCl, HgS S 2- Zn 2+ 6
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Ionic Solids: (3) ZnS Crystal Structure 7
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Ionic Solids: (3) ZnS Crystal Structure 8
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(a) Find the number of Ti atoms per unit cell. (b) Find the number of O atoms per unit cell. (c) Determine the formula. red = O grey = Ti Rutile is a mineral composed of Ti and O. Its unit cell is shown below. 9
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This note was uploaded on 09/13/2011 for the course CHEM 102 taught by Professor Todd during the Spring '08 term at UNC.

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Chap13_Part1 - Covalent-Network Solids These materials are held together by networks of covalent bonds(e.g quartz or SiO2 They are very hard and

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