Presentation on theme: "Solids differ: Hardness Melting point Flexibility Conductivity Solids form crystal lattice structures: Repeating pattern of molecules Determined by x-ray."— Presentation transcript:
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
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
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)
Molecular Crystals Neutral (nonpolar) molecules held together by weak intermolecular forces (LDF) Low melting pt Soft Non- conductive Solubility in water?
Why does ice float? When water molecules freeze, they form a hexagonal crystal of H 2 O molecules linked by H bonds.
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
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?
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