CH. 12 SOLIDS & MODERN MATERIALS CLASSIFICATION STRUCTURE >unit cell RECALL 3 physical states solid -- liquid -- gas Diamond -- Wax Mallable-Ductile --- Brittle Type of bonds Metallic Solids -metallic bonding, sea “e-” -strong w/o brittle -conduct electricity Ionic Solids -electrostatic attraction -cation/anion Covalent Network -covalent bonds -hardness/semiconductor prop Molecular Solids -intermol forces, weak -soft/lowm.p.

STRUCTURE Crystalline solids Amorphous solids >ordered arrangement >random arrangement >flat surfaces >no defined surface/shape >regular shapes; rhombic, cubic, Unit Cell – repeating unit of unique arrangement; parallelogram of size & shape defined by vectors Crystal Lattice – geometric pattern of pts Lattice Pts – pts in crystal w/ same environment Primitive – lattice pt each corner

Unit Cell >cells fit together to cover area w/ no gaps, thus square, rectangle, hexagon, rhomboid, parallelogram >Other polygons leave gaps

= vector length, but angle not 90o or 120o LATTICES 2D – 5 shapes 2 vectors 5th Rhombic Lattice = vector length, but angle not 90o or 120o vary length vectors = length vector 90o not 120o 90o

LATTICES 3D – 7 lattices 3 vectors Figure 11-02 Title: Molecular-level comparison of gases, liquids, and solids. Caption: The particles can be atoms, ions, or molecules. The density of particles in the gas phase is exaggerated compared with most real situations. Notes: Keywords: 6

Centered Lattices Additional lattice pts at specific locations in unit cell

METALLIC SOLIDS Bonding too strong for dispersion, not many val e- to form covalent bonds, so metallic bonding due to delocalized e- e- e- malleable - ductile behavior indicates slip pass each other e- e- e- e-

radioactive, Po Na, W Ag, Au Figure 11-03 Title: Intermolecular attraction. Caption: Comparison of a covalent bond (an intramolecular force) and an intermolecular attraction. Because intermolecular attractions are weaker than covalent bonds, they are usually represented by dashes or dots. Notes: Keywords: Rare Fe, Cr, Al, Pb, Cu, radioactive, Po Na, W Ag, Au 9

>efficient way to layer Close Packing >short valence e- >efficient way to layer Figure 11-02 Title: Molecular-level comparison of gases, liquids, and solids. Caption: The particles can be atoms, ions, or molecules. The density of particles in the gas phase is exaggerated compared with most real situations. Notes: Keywords: 10

ALLOYS >2+ elements w/ properties of a metal >used to modify pure metal elements >4 categories substitutional, interstitial, heterogeneous, intermetallic mixtures

Types of Alloys Substitutional alloys: A second element takes the place of a metal atom. Interstitial alloys: A second element fills a space in the lattice of metal atoms. Heterogeneous alloys: components not dispersed uniformly

Intermetallic Compounds compounds, not mixtures distinct properties, definite composition (since they are compounds) ordered, rather than randomly distributed

Molecular Solids Consist of atoms or molecules held together by weaker forces (dispersion, dipole–dipole, or hydrogen bonds). Shape (ability to stack) matters for some physical properties, like boiling point. Graphite is an example.

Two Other Types of Solids Polymers contain long chains of atoms connected by covalent bonds; the chains can be connected to other chains by weak forces. These molecules have different properties than small molecules or metallic or ionic compounds. Nanomaterials are crystalline compounds with the crystals on the order of 1–100 nm; this gives them very different properties than larger crystalline materials.

Polymers Polymers are molecules of high molecular weight made by joining smaller molecules, called monomers. There are two primary types of polymers: Addition polymers are formed when a bond breaks, and the electrons in that bond make two new bonds. Condensation polymers are formed when a small molecule is removed between two large molecules.

Some Common Polymers

Nanomaterials Particles that have three dimensions on the 1–100 nm size Their properties are the study of many labs around the world.

Metals on the Nanoscale Finely divided metals can have quite different properties than larger samples of metals. Would you like “red gold” as in many old stained glass windows?