• 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

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

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

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

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

• 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

• 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)

• Rigid, multidimensional array of covalently bonded atoms

• Neutral, covalently bonded molecules held together by intermolecular attractive forces

Clusters

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

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

• 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)

Allotropes of Phosphorus

White, Red

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

Allotrope: Boron

• more allotropes than any other element
• most common in S8 ring

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

• 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)

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