Chapter 13: Solids and Modern Materials Overview

X-ray diffraction

Technique to analyze atomic arrangements in crystals.

Atomic planes

Layers in crystals, spaced about 100 pm apart.

Diffraction patterns

Interference patterns formed by X-ray interactions.

Path length

Distance traveled by rays in diffraction.

Bragg's Law

nλ = 2d×sin(θ) relates wavelength and atomic spacing.

Unit cell

Smallest repeating unit showing atomic arrangement.

Crystal lattice

Regular arrangement of atoms in a crystal.

Coordination number

Number of neighboring particles in contact.

Packing efficiency

Volume percentage occupied by particles in unit cell.

Cubic unit cells

Unit cells with 90° angles and equal edge lengths.

Simple cubic

Unit cell with one particle per cell.

Body-centered cubic

Unit cell with two particles, one at center.

Face-centered cubic

Unit cell with four particles, one at each face.

Coordination number of simple cubic

6, due to corner particle contacts.

Coordination number of body-centered cubic

8, due to center particle contacts.

Coordination number of face-centered cubic

12, due to face particle contacts.

Lattice parameters

a, b, c: lengths of unit cell edges.

Unit cell volume

Measured in ų or pm³, describes cell size.

Spherical particles

Assumed shape for unit cell calculations.

Hexagonal close packing

Efficient arrangement of spheres in layers.

Edge length of unit cell

Denoted as l or a, critical for calculations.

Density calculation

Mass per unit volume, important for element identity.

Atomic weight

Mass of one mole of atoms, in g/mol.

Hexagonal Closest-Packed

Atoms arranged in close-packed hexagonal layers.

Cubic Closest-Packed

Atoms arranged in cubic closest-packed layers.

Crystalline Solids

Solids with ordered particle arrangements.

Molecular Solids

Solids composed of molecules at lattice sites.

Ionic Solids

Solids made of ions occupying lattice sites.

Atomic Solids

Solids classified by attractive forces between atoms.

Polymorphs

Different crystalline structures of the same compound.

Coordination Number

Number of close cation-anion interactions in crystals.

Coulombic Forces

Strong forces holding ionic solids together.

Metallic Bonding

Bonding involving a sea of mobile electrons.

Nonbonding Atomic Solids

Held together by weak dispersion forces.

Metallic Atomic Solids

Held together by metallic bonding, varying melting points.

Network Covalent Solids

Held together by covalent bonds, very hard.

Dispersion Forces

Weak intermolecular forces in molecular solids.

Dipole-Dipole Attractions

Intermolecular forces between polar molecules.

Hydrogen Bonds

Strong intermolecular forces involving hydrogen atoms.

Melting Points

Temperature at which solids transition to liquids.

CsCl Structure

Coordination number of cesium chloride is 8.

NaCl Structure

Coordination number of sodium chloride is 6.

Zinc Blende Structure

Coordination number of zinc blende is 4.

Atomic Radii

Average size of atoms in a crystal structure.

Density Calculation

Determining density using unit cell dimensions.

S2-

Anion occupying corners and faces in unit cell.

Zn2+

Cation located in tetrahedral holes of ZnS.

Tetrahedral holes

Spaces in crystal lattice for cation placement.

Density calculation

Mass per unit volume, expressed in g/cm³.

Fluorite Structure

CaF2 arrangement with F- and Ca2+ ions.

Coordination number

Number of nearest neighbors surrounding an ion.

CaF2

Calcium fluoride, 1:2 cation to anion ratio.

Antifluorite structure

Occurs with cation:anion ratio of 2:1.

Network Covalent Solids

Solids with atoms bonded by covalent bonds.

Graphite

Carbon allotrope with layered structure and dispersion forces.

Bond length in graphite

142 pm, distance between bonded carbon atoms.

sp2 hybridization

Carbon bonding with three sigma and one pi bond.

Diamond

Carbon allotrope with tetrahedral sp3 bonding.

High melting point

Temperature around 3800 °C for carbon allotropes.

Buckminsterfullerenes

C60 carbon structure resembling a soccer ball.

Nanotubes

Cylindrical structures made of interconnected carbon rings.

Single-walled nanotubes

One layer of interconnected carbon rings.

Multiwalled nanotubes

Concentric layers of interconnected carbon rings.

Silicates

Compounds containing SiO4 tetrahedra, major crust component.

Quartz (SiO2)

Common silicate mineral with tetrahedral structure.

Ceramics

Inorganic solids made from powders and heat.

Aluminosilicates

Silicates containing aluminum, used in ceramics.

Kaolinite

Clay mineral, Al2Si2O5(OH)4, used in ceramics.

Oxide Ceramics

Common ceramics like Al2O3 and MgO.

Refractory Materials

Materials used in high-temperature applications.

Nonoxide Ceramics

Ceramics like Si3N4, BN, and SiC.

Si3N4

Network covalent solid similar to silica.

BN

Isoelectronic with C2, forms diamond-like structure.

Portland Cement

Powdered mixture mainly of limestone and silica.

Concrete

Widely used building material made from cement.

Borosilicate Glass

Glass with added boric acid for durability.

Vitreous Silica

Hard, low thermal expansion, transparent to UV.

Leaded Glass

Glass containing PbO, high refractive index.

Soda-Lime Glass

Common window glass, 70% silica content.

Molecular Orbitals

Formed from combining atomic orbitals.

Band Theory

Describes delocalized orbitals in solids.

Valence Band

Band of bonding molecular orbitals.

Conduction Band

Band of antibonding molecular orbitals.

Band Gap

Energy gap between valence and conduction bands.

Conductors

Continuous valence and conduction bands.

Semiconductors

Have band gap, can conduct electricity.

Insulators

Large band gap restricts electron promotion.

Doping

Adding impurities to increase semiconductor conductivity.

n-type Semiconductors

Doped with electron-rich impurities.

p-type Semiconductors

Doped with electron-deficient impurities.

Diode

Allows current flow in one direction.

Polymers

Large molecules formed from repeated monomers.

Monomers

Small molecules that link to form polymers.

Polymerization

Process of linking monomer units together.

Condensation Polymerization

Involves elimination of small molecules during formation.