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

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

LATTICES 3D – 7 lattices 3 vectors

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 - malleable - ductile behavior indicates slip pass each other e-e- e-e- e-e- e-e- e-e- e-e-

Rare Fe, Cr, Al, Pb, Cu, radioactive, Po Na, W Ag, Au

Close Packing >short valence e - >efficient way to layer

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

SUBSTITUTIONAL