Ch. 12 Solids: Crystals, Alloys, and Polymers

Solid

A state of matter characterized by a definite shape and volume, where particles are closely packed together and vibrate in fixed positions.

1. Amorphous

2. Crystalline

What are the 2 types of solids?

Amorphous

Solids in which the atoms and molecules are not organized in a definite lattice pattern, has a melting point range

Examples: Glass, rubber, plastics, butter, wax, gel

Crystalline

Highly ordered solids with a definite geometric structure and a sharp melting point.

Examples: Diamond, table salt, ice, most metals (silver and gold)

1. Metallic

2. Ionic

3. Covalent Network

4. Molecular

What are the 4 types of crystalline solids?

Metallic Crystalline Solid

Particle: Metal atoms

Interaction: Metallic bonds

Physical Properties: good conductors of heat and electricity, shiny, ductile, malleable, soft or hard

Examples: Au, Pt, Ag, V

Ionic Crystalline Solid

Particle: Cations and anions

Interaction: Ionic bonds

Physical Properties: high melting point, conduct electricity when melted or dissolved, hard and brittle

Examples: NaCl, KI, Na₂SO₄

Covalent Network Crystalline Solid

Particle: Atoms

Interaction: Covalent bonds

Physical Properties: very high melting point, poor conductors, very hard

Examples: Diamond, SiC, C, SiO₂

Molecular Crystalline Solid

Particle: Molecules

Interactions: Intermolecular forces

Physical Properties: Low melting point, poor conductors, soft

Examples: C₁₂H₂₂O₁₁ (sucrose, table sugar)_, C₆H₆O (ethanol)

Ionic

What kind of crystalline solid is this: KNO₃

Covalent

What kind of crystalline solid is this: SiC

Molecular

What kind of crystalline solid is this: C₆H₁₂O₆

Metallic

What kind of crystalline solid is this: Ag

Molecular

You pick up an unknown and notice that it melts at 86^oC. The solid has a dull appearance, and deforms when pressed in your hands. What type of crystalline solid is this?

Unit Cell

The smallest repeating unit of a crystalline solid that retains the overall symmetry and structure of the crystal.

Simple Cubic

A type of crystal lattice where atoms are arranged at the corners of a cube, with one atom per unit cell.

• 1/8 of an atom at each corner

• 1 entire atom in center and a total of 2 atoms

• Coordination number → 6

Body-centered Cubic

A type of crystal lattice where atoms are located at the corners of a cube and one atom is situated at the center of the cube.

• 1/8 in each corner and 1 atom in center

• 2 total atoms in cell

  • Coordination number → 8

Face-centered Cubic

A type of crystal lattice where atoms are located at each corner of the cube and at the center of each face.

• 1/8 in each corner and ½ atom on each face

• 4 total atoms in cell

• Coordination number → 12