Post on 18-Jan-2016
CH. 12 SOLIDS & MODERN MATERIALS
CLASSIFICATION STRUCTURE >unit cell
RECALL
3 physical states solid -- liquid -- gas
Diamond -- WaxMallable-Ductile --- BrittleType 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.
STRUCTURECrystalline 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 vectorsCrystal Lattice – geometric pattern of ptsLattice Pts – pts in crystal w/ same environmentPrimitive – 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
LATTICES2D – 5 shapes 2 vectors
vary length vectors = length vector90o not 120o 90o
5th Rhombic Lattice= vector length, but angle not 90o or 120o
LATTICES3D – 7 lattices 3 vectors
Centered LatticesAdditional lattice pts at specific locations in unit cell
METALLIC SOLIDS
Bonding too strong for dispersion, not many val e- to form covalent bonds, sometallic bonding due to delocalized e-
malleable - ductile behavior indicates slip pass each other
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