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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) - PowerPoint PPT Presentation
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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
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 H2O 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– SiO2: 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?
Summary
Homework
Pg. 254 #: 1-4,6-9
Self Quiz Pg. 261Chapter Review Pg. 262