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Metallic Bonds

answer

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

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n - type semiconductor

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excess electrons contributed by electro rich dopant atoms
If two atoms have more than +8 valence elecrtrons combined.

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p-type semiconductor

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holes due to elecron deficient dopant atoms
The sum of the valence electrons are less than 8.

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What is doping, and criteria?

answer

replace atoms with element of similar atomic radius and with a different # of valence electrons.

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Define Crystalline Solid and Crystalline Lattice

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Crystalline Lattice: Ordered three dimensional array of particles in a crystalline solid
Crystalline Solid: Substance exhibiting an ordered array of atoms, ions or molecules

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Define Alloy vs Ore

answer

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

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Substitutional Alloy

answer

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)

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Covalent Network Solids

answer

Rigid, multidimensional array of covalently bonded atoms

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Molecular Solids

answer

Neutral, covalently bonded molecules held together by intermolecular attractive forces

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Clusters

answer

Ordered collections of atoms that are larger than typical molecular solids, smaller than network covalent solids.

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Allotropes

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Different molecular structures of an element
i.e allotrope of carbon, diamond vs graphite

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Graphite vs Diamond

answer

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)

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Fullerene

answer

3 dimensional network of sp2 hybridized carbon atoms fuzed in 5 and 6 membered rings. like a soccer ball.

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Allotropes of Phosphorus
White, Red

answer

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

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Allotrope: Boron

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forms B12 cluster arranged in icosahedral

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Allrtope: Sulfur

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more allotropes than any other element
most common in S8 ring

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Other Ionic Crystals: Sphalerite

answer

fcc unit cell of Sn2- with Zn2+ in four of the 8 tetrahedral holes

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Polymorphs vs Amorphous Solids

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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)

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Polymorphs of Silica

answer

Quartz: hexagonal ordering of SiO2 tetrahedra (Network solid)
Obsidian: amorphous/glassy polymorph of Silica.

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