The Solid State: The Solid State: Types of solids

Crystalline solids have a regular arrangement 1. Ionic Solids (NaCl) 2. Molecular solids (sucrose) 3. Atomic or elemental solids (graphite, diamond)

Properties of a solid are determined by the nature of the forces between their particles (intermolecular/intramolecular) Properties of a solid are determined by the nature of the forces between their particles (intermolecular/intramolecular)

Ionic Solids: oppositely charged ions are held together by strong forces of attraction oppositely charged ions are held together by strong forces of attraction Conduct a current in solution as ions are free to move Conduct a current in solution as ions are free to move Stable substances with high melting points (solids at room temp) Stable substances with high melting points (solids at room temp)

Ionic Solids Larger negative ions are packed together with smaller positive ions occupying spaces between them. Larger negative ions are packed together with smaller positive ions occupying spaces between them.

Molecular Solids Sulfur (S 8 ) Phosphorus (P 4 ) Carbon Dioxide (CO 2 )

Forces are much weaker than in ionic solids Forces are much weaker than in ionic solids London dispersion forces London dispersion forces may have dipole-dipole attractions may have dipole-dipole attractions  melt at lower temperatures  melt at lower temperatures

Atomic Solids Properties vary greatly, depending on how the atoms interact Properties vary greatly, depending on how the atoms interact Noble gases Noble gases London dispersion forces London dispersion forces very low melting points ( Neon: º C ) very low melting points ( Neon: º C ) Diamond (carbon) Diamond (carbon) covalent bonds between carbon atoms form a network solid covalent bonds between carbon atoms form a network solid very high melting point (>3500  C) very high melting point (>3500  C)

Bonding in Metals Bonds are strong and nondirectional Bonds are strong and nondirectional difficult to separate atoms, but easy to slide them past each other difficult to separate atoms, but easy to slide them past each other

Electron sea model Electron sea model valence electrons are shared and free to move around (makes metals good conductors) valence electrons are shared and free to move around (makes metals good conductors) Click here for an animation

This bonding accounts for malleability, ductility, high melting points and durability of metals. This bonding accounts for malleability, ductility, high melting points and durability of metals. Movement of electrons make metals good conductors Movement of electrons make metals good conductors

Alloys substances that contain a mixture of elements and have metallic properties substances that contain a mixture of elements and have metallic properties There are 2 types of alloys There are 2 types of alloys substitutional alloy substitutional alloy interstitial alloy interstitial alloy

Substitutional alloys some atoms are replaced by similarly sized atoms some atoms are replaced by similarly sized atoms Brass: 67% Cu, 33% Zn Brass: 67% Cu, 33% Zn

Sterling silver: 93% Ag, 7% Cu Sterling silver: 93% Ag, 7% Cu

Interstitial alloy Inter: between; stitial: spaces Inter: between; stitial: spaces Smaller atoms fit in “holes” (interstices) between atoms Smaller atoms fit in “holes” (interstices) between atoms Steel: Iron and carbon Steel: Iron and carbon Carbon atoms form directional bonds, which give strength, increase hardness and decrease ductility Carbon atoms form directional bonds, which give strength, increase hardness and decrease ductility

Amount of carbon affects type of steel Amount of carbon affects type of steel Mild steels (<0.2%C): nails, cables, chains Mild steels (<0.2%C): nails, cables, chains

Medium steels ( %C): structural steel, rails Medium steels ( %C): structural steel, rails

High-carbon steels ( %C): springs, tools, cutlery High-carbon steels ( %C): springs, tools, cutlery

Stainless steel Stainless steel Chromium and nickel atoms are substituted for some iron to better resist corrosion Chromium and nickel atoms are substituted for some iron to better resist corrosion