Chem 108 1st Edition Lecture 6 Current LectureChapter 12 continuedAlloys: - Metallic material that blends atoms of a host metal with atoms of one or more other elements to change the properties of the host metal. o Substitutional alloys: atoms of the non-host metal replace host atoms in the crystal latticeo Interstitial alloy: when the non-host atoms accommodate to the empty spaces or holes in the crystal lattice o Homogenous Alloys: Solid solution in which atoms of host and added elements are randomly and uniformly distributed. o Heterogenous Alloys: Matrix of host metal atoms with “islands” of atoms of added elements interspersed.o How to predict the crystal structure of a two-element alloy: (rnon-host/rhost)o It depends on the Crystal lattice and hole type. If its higher than the stated range then it is a Substitutional alloy, but if it’s within the stated range then it is a interstitial alloy.o hcp or ccp and tetrahedral: 0.22-0.41o hcp or ccp and octahedral: 0.41-0.73o Cubic packing and cubic 0.73-1.00- Ores: Naturally occurring compounds or mixtures of compounds from which elements can be extracted.Allotropes: - Different molecular structures of an element. The different structures of the same element give it different physical properties. Allotropes of Carbon- Allotropes of Carbon: Diamond: o Network covalent solid. o All carbon atoms sp3 - hybridized; tetrahedral configuration. o Hard; non-conductive; high- Graphite: These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.o 2-dimensional covalent network of sp2 -hybridized carbon atoms in sheets of fused 6-membered rings. o Sheets held together by dispersion forces. o Soft; good lubricant; conductive.Allotropes of Phosphorus - White Phosphorus: o Molecular solid based on P4 tetrahedra. o Waxy, soft solid; burns in air.- Red Phosphorus:o Polymer of covalently linked P4 tetrahedra. o Stable in air.Salt Crystals: Ionic Solids - Ionic Solids: o Monoatomic or polyatomic ions held together by ionic bonds. o Most are crystalline (e.g., NaCl)Metallic Bonds:- Dense packing of metal atoms results in overlap of large number of valence orbitals. - Large number of interactions = strong overall interaction.- Limited sharing of electrons between any two atoms = weak bonds between individual atoms.- Band Theory: o An extension of molecular orbital theory; describes bonding in solids. - Valence Bands: o Bands of orbitals that are filled or partially filled by valence electrons. - Conduction Bands: o Higher-energy unoccupied bands in which electrons are free to migrate.- Band Gap (Eg ): o Energy gap between the valence and conduction bands. - Semiconductor: o A substance (metalloid) whose conductivity can be made to vary over several orders of magnitude by adding “dopants.” o Doping is a process where you replace some atoms of the semiconductor with atoms of similar atomic radius but different number of valence electrons. A dopant is that atom that does the replacingo n-type semiconductor—excess electrons contributed by electron-rich dopant atoms. o p-type semiconductor—“+” holes due to electron poor dopant atoms.Superconductor: Material having zero resistance to flow of electric current. - Critical temperature (Tc ): Temperature below which a material becomes a superconductor. - Superconducting alloys, like Nb3Sn, must be cooled to 20 K to remain superconducting.Salt Crystals: - Ionic Solids: Monoatomic or polyatomic ions held together by ionic bonds. Most are crystalline- Polymorphs: Same empirical formulas but different crystal structures/properties. - Amorphous solids: Non-crystalline, disordered array of atoms, ions or particles in a solid state (e.g., glass)Crystalline Solids of Nonmetals:- Covalent network solids: Rigid, three-dimensional array of covalently bonded atoms. - Molecular solids: 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.X-ray diffraction (XRD): - Technique for determining arrangement of atoms or ions in a crystal. It analyzes the pattern that results when X-rays are scattered after bombarding the crystal. - Bragg Equation: nλ  2dsinθ o Where θ = angle of diffraction of X-rays. o d = spacing between layers of ions/atoms in a