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