Crystalline Solids and Their Structures

Unit Cell

Basic repeating unit of the arrangement of particles in a crystalline solid.

Simple Cubic Unit Cell

Square-packing arrangement; particles located at 8 corners of cubic unit cell. Coordination number = 6.

Body-Centered Cubic (bcc)

Square packing arrangement in which particles are located at 8 corners and in center of cubic unit cell. Coordination number = 8.

Face-Centered Cubic (fcc)

Closest packing unit cell in which atoms are located on the 8 corners and 6 faces of a cube. Coordination number = 12.

Hexagonal Closest-Packed (hcp)

A crystal structure in which the layers of atoms or ions have an a-b-a-b-a-b stacking pattern.

Cubic Closest-Packed (ccp)

A crystal structure in which the layers of atoms and ions have an a-b-c-a-b-c-a-b-c stacking pattern.

Crystalline Solid

A solid made of an ordered array of atoms, ions, or molecules.

Crystal Lattice

Ordered three-dimensional array of particles in a crystalline solid.

Coordination Number

The number of atoms with which each atom is in direct contact.

Amorphous Solids

Particles are randomly arranged and have no ordered long-range structure. Example - rubber.

Crystalline Solids

Particles have an ordered arrangement extending over a long range.

Ionic Solids

A type of crystalline solid formed by ionic bonds.

Molecular Solids

A type of crystalline solid formed by molecular interactions.

Atomic Solids

Crystalline solids that can be metallic, network, or non-bonding.

Metallic Solids

A type of atomic solid characterized by metallic bonds.

Network Solids

A type of atomic solid where atoms are connected by covalent bonds in a continuous network.

Non-bonding Solids

A type of atomic solid that does not involve bonding between atoms.

Graphite

One of the common crystalline allotropes of carbon.

Diamond

Another common crystalline allotrope of carbon.

Fullerenes

Molecular structures composed entirely of carbon, forming a hollow sphere, ellipsoid, or tube.

Nanotubes

Cylindrical structures made of carbon atoms arranged in a hexagonal lattice.

Silicate

A compound containing silicon and oxygen, often forming the basis of minerals.

Quartz

A mineral with the empirical formula SiO2, consisting of tetrahedral SiO4 structural units.

Glass

An amorphous solid that also has the empirical formula SiO2 but consists of tetrahedral SiO4 structural units.

Atoms in Body Center Cubic Unit Cell

1 atom from 8 corners, total 2 atoms per unit cell.

Atoms in Face-Centered Cubic Unit Cell

1 atom from corners, 3 atoms from faces, total 4 atoms per unit cell.

Polonium Atom Radius Calculation

Given edge length l = 334 pm, calculate radius in picometers and centimeters.

Density of Polonium

Density calculation in g/cm3 using l = 334 pm = 3.34 x 10^-8 cm.

Density of Metal in Face-Centered Cubic Structure

Calculate density if the atomic mass is 87.62 g/mol and radius is 1.97 x 10^-8 cm.

Coordination Number in NaCl

Coordination number = 6.

Na:Cl Ratio in NaCl

Na:Cl = (¼ × 12) + 1: (⅛ × 8) + (½ × 6) = 4:4 = 1:1.

Atomic Solids Nonbonding

Noble gases in solid form held by weak dispersion forces, very low melting point.

Atomic Solids Covalent Network

Examples include diamond, graphite, fullerene, and silica (SiO2).

Carbon Allotropes

Different structural forms of carbon including diamond and graphite.

Silicates

Make up ~90% of Earth's crust, consist of extended arrays of Si—O.

Semiconductors

Materials like silicon or germanium with conductivity between metals and insulators.

Superconductors

Materials that lose all electrical resistance below a characteristic temperature.

Metallic Hydrogen

A new material created by squeezing hydrogen, potentially a highly efficient electricity conductor.