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CHE 132 - Exam 3
Chp 12, 18, 19, 21
19
Chemistry
Undergraduate 2
08/08/2013

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Term
Metallic Bonds
Definition
  • Dense packing
  • over lap of large number valence orbitals
  • large interaction = strong
  • limited sharing fo e- between any two atoms, weak bonds between individual atoms
Term
n - type semiconductor
Definition
  • excess electrons contributed by electro rich dopant atoms
  • If two atoms have more than +8 valence elecrtrons combined.
Term
p-type semiconductor
Definition
  • holes due to elecron deficient dopant atoms
  • The sum of the valence electrons are less than 8.
Term
What is doping, and criteria?
Definition
  • replace atoms with element of similar atomic radius and with a different # of valence electrons.
Term
Define Crystalline Solid and Crystalline Lattice
Definition
  • Crystalline Lattice: Ordered three dimensional array of particles in a crystalline solid
  • Crystalline Solid: Substance exhibiting an ordered array of atoms, ions or molecules
Term
Define Alloy vs Ore
Definition
  • Alloy: Metallic material that blends atoms of host metal with atoms of one or more other elements to change its properties of the host metal. 2nd element doesn't have to be a metal.
  • Ore: naturally occuring compounds or mixtures of compounds from which elements can be extracted
Term
Substitutional Alloy
Definition
  • atoms of added elements replace host metal in crystal lattics
  • Forms between metals of similar radii (15%)
  • i.e Bronze, Pewter, Ferrous Alloys (stainless steel)
Term
Covalent Network Solids
Definition
  • Rigid, multidimensional array of covalently bonded atoms
Term
Molecular Solids
Definition
  • Neutral, covalently bonded molecules held together by intermolecular attractive forces
Term

Clusters

Definition
  • Ordered collections of atoms that are larger than typical molecular solids, smaller than network covalent solids.
Term
Allotropes
Definition
  • Different molecular structures of an element
  • i.e allotrope of carbon, diamond vs graphite
Term
Graphite vs Diamond
Definition
  • Graphite: 2 dimensional covalent network of sp2 hybridized carbon atoms in sheets of fused 6 membered rings
  • soft, lubricant, sheets held together by dispersion forces
  • Diamond: network covalent solid, all carbons in sp3 hybridized tetrahedral config. (hard, non-conductive)
Term
Fullerene
Definition
3 dimensional network of sp2 hybridized carbon atoms fuzed in 5 and 6 membered rings. like a soccer ball.
Term

Allotropes of Phosphorus

White, Red

Definition
  • White Phosphorus: Molecular solid pased on P4 tetrahedra.
  • Red Phosphorus: polymer of covalently linked P4 tetrahedra , stable in air, network soild
Term

Allotrope: Boron

 

Definition
forms B12 cluster arranged in icosahedral
Term
Allrtope: Sulfur
Definition
  • more allotropes than any other element
  • most common in S8 ring
Term
Other Ionic Crystals: Sphalerite
Definition
  • fcc unit cell of Sn2- with Zn2+ in four of the 8 tetrahedral holes
Term
Polymorphs vs Amorphous Solids
Definition
  • Polymorphs: Same empirical formula but different crystal structure/properties
  • Amorphous Solids: non-crystalline, disordered array of atoms ions or particules in a solid state (e.g glass)
Term
Polymorphs of Silica
Definition
  • Quartz: hexagonal ordering of SiO2 tetrahedra (Network solid)
  • Obsidian: amorphous/glassy polymorph of Silica. 
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