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Solids differ: Hardness Melting point Flexibility Conductivity

Structure and Properties of SOLIDS. Solids differ: Hardness Melting point Flexibility Conductivity Solids form crystal lattice structures: Repeating pattern of molecules Determined by x-ray crystallography Categories of solids: Ionic (metals + nonmetals) Metallic (metals)

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Solids differ: Hardness Melting point Flexibility Conductivity

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  1. Structure and Properties of SOLIDS Solids differ: • Hardness • Melting point • Flexibility • Conductivity Solids form crystal lattice structures: • Repeating pattern of molecules • Determined by x-ray crystallography Categories of solids: • Ionic (metals + nonmetals) • Metallic (metals) • Molecular (nonmetals) • Covalent Network • Metalliod compounds (SiC, SiO2) • carbon compounds C (s) • diamond, graphite

  2. Ionic Crystals • crystal lattice • electrostatic attraction b/w ions of opposite charge (ionic bonding) • ions held in fixed position • Hard • Brittle • Good electrical conductivityasa liquid and in aqueous solution • High melting points • Solid  liquid (weakenionic attraction,  distance betweenions) • Held together by Ionic forces: STRONGEST

  3. Metallic Crystals Metallic Bonding: fixed nuclei, loosely held mobile valence e- (“e- sea”  delocalized e-) • Shiny/silvery: metallic e- absorb energy from all λ • Easily oxidized= loose e- =  ionization energy=lose e- • Flexible: Strong non-directional bonding= electron sea • Strength: closely packed crystal • Electrical conductivity • Thermal conductivity • Soft (Pb) or hard (Cr) •  mp (Hg) or mp (W)

  4. Molecular Crystals • Neutral (nonpolar) molecules held together by weak intermolecular forces (LDF) • Lowmelting pt • Soft • Non- conductive • Solubility in water?

  5. Why does ice float? • When water molecules freeze, they form a hexagonal crystal of H2O molecules linked by H bonds.

  6. Covalent Networks • Highest melting pt • held together by continuous directional covalent bonds • C-C bonds in a network are interlocked and are stronger than the sum of individual C-C bonds • Hard • Stronger than ionic or molecular crystals • Diamond- large tetrahedral network • SiO2: Quartz (a) and Glass (b) • Which do you think is stronger? • Brittle • Insoluble • Non-conductive: e- movement restricted by network

  7. Covalent Networks of CARBON • C can form 4 bonds • Many structures • Nanotechnology? • Graphite is able to conduct electricity and is a lubricant • What is different about graphite?

  8. Summary

  9. Homework Pg. 254 #: 1-4,6-9 Self Quiz Pg. 261 Chapter Review Pg. 262

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