The Solid State:The Solid State:

Types of solidsTypes of solids

Crystalline solids have a regular Crystalline solids have a regular arrangementarrangement

1.1. Ionic Solids (NaCl)Ionic Solids (NaCl)

2.2. Molecular solids (sucrose)Molecular solids (sucrose)

3.3. Atomic or elemental solids Atomic or elemental solids (graphite, diamond)(graphite, diamond)

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

Ionic Solids:Ionic Solids:

oppositely charged ions are held together oppositely charged ions are held together by strong forces of attractionby strong forces of attraction

Conduct a current in solution as ions are Conduct a current in solution as ions are free to movefree to move

Stable substances with high melting points Stable substances with high melting points (solids at room temp)(solids at room temp)

Ionic SolidsIonic SolidsLarger negative ions are packed together Larger negative ions are packed together

with smaller positive ions occupying with smaller positive ions occupying spaces between them.spaces between them.

Molecular SolidsMolecular Solids

Sulfur (S8)

Phosphorus (P4)

Carbon Dioxide (CO2)

Forces are much weaker than in ionic Forces are much weaker than in ionic solidssolidsLondon dispersion forcesLondon dispersion forcesmay have dipole-dipole attractionsmay have dipole-dipole attractions

melt at lower temperaturesmelt at lower temperatures

Atomic SolidsAtomic SolidsProperties vary greatly, depending on how Properties vary greatly, depending on how

the atoms interactthe atoms interactNoble gasesNoble gases

London dispersion forcesLondon dispersion forcesvery low melting points ( Neon: -248.67 º C )very low melting points ( Neon: -248.67 º C )

Diamond (carbon)Diamond (carbon)covalent bonds between carbon atoms form a covalent bonds between carbon atoms form a

network solidnetwork solidvery high melting point (>3500very high melting point (>3500 C)C)

Bonding in MetalsBonding in MetalsBonds are strong and nondirectionalBonds are strong and nondirectional

difficult to separate atoms, but easy to slide difficult to separate atoms, but easy to slide them past each otherthem past each other

Electron sea modelElectron sea modelvalence electrons are shared and free to valence electrons are shared and free to

move around (makes metals good move around (makes metals good conductors)conductors)

Click here for an animation

This bonding accounts for malleability, This bonding accounts for malleability, ductility, high melting points and durability ductility, high melting points and durability of metals.of metals.

Movement of electrons make metals good Movement of electrons make metals good conductorsconductors

AlloysAlloyssubstances that contain a mixture of substances that contain a mixture of

elements and have metallic propertieselements and have metallic propertiesThere are 2 types of alloysThere are 2 types of alloys

substitutional alloysubstitutional alloy interstitial alloyinterstitial alloy

Substitutional alloysSubstitutional alloyssome atoms are replaced by similarly some atoms are replaced by similarly

sized atomssized atomsBrass: 67% Cu, 33% ZnBrass: 67% Cu, 33% Zn

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

Interstitial alloyInterstitial alloy Inter: between; stitial: spacesInter: between; stitial: spacesSmaller atoms fit in “holes” (interstices) Smaller atoms fit in “holes” (interstices)

between atomsbetween atomsSteel: Iron and carbonSteel: Iron and carbon

Carbon atoms form directional bonds, which Carbon atoms form directional bonds, which give strength, increase hardness and give strength, increase hardness and decrease ductilitydecrease ductility

Amount of carbon affects type of steelAmount of carbon affects type of steelMild steels (<0.2%C): nails, cables, chainsMild steels (<0.2%C): nails, cables, chains

Medium steels (0.2-0.6%C): structural steel, Medium steels (0.2-0.6%C): structural steel, railsrails

High-carbon steels (0.6-1.5%C): springs, High-carbon steels (0.6-1.5%C): springs, tools, cutlerytools, cutlery

Stainless steelStainless steelChromium and nickel atoms are substituted Chromium and nickel atoms are substituted

for some iron to better resist corrosionfor some iron to better resist corrosion