1. 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, SiO 2 ) – carbon compounds C (s) diamond, graphite Structure and Properties of SOLIDS

2. Ionic Crystals crystal lattice electrostatic attraction b/w ions of opposite charge (ionic bonding) ions held in fixed position Hard Brittle Good electrical conductivity as a liquid and in aqueous solution High melting points – Solid  liquid (weaken ionic attraction,  distance between ions) – 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) Low melting pt Soft Non- conductive Solubility in water?

5. Why does ice float? When water molecules freeze, they form a hexagonal crystal of H 2 O 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 – SiO 2 : 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