Crystal Lattices and Metallic Bonding

Study Notes

A crystal lattice is a three-dimensional arrangement of atoms, ions, or molecules in a repeating pattern
Crystal lattices can be described by:
- Unit cell: the smallest three-dimensional unit that repeats to form the crystal lattice
- Lattice parameters: the dimensions of the unit cell (a, b, c, α, β, γ)
- Crystal system: the symmetry of the lattice (e.g. cubic, tetragonal, orthorhombic, etc.)

Metallic bonding occurs between metal atoms in a crystal lattice
Characteristics of metallic bonding:
- Delocalization of electrons: electrons are free to move throughout the lattice
- Sea of electrons: a "sea" of electrons surrounds the metal ions
- High electrical conductivity: due to the mobility of electrons
- Malleability and ductility: metal atoms can be easily deformed without breaking

Ceramic materials are inorganic, non-metallic solids
Characteristics of ceramic materials:
- Hardness and brittleness: ceramic materials are often hard and brittle
- High melting points: ceramic materials have high melting points
- Low electrical conductivity: ceramic materials are often insulators
- Chemical inertness: ceramic materials are resistant to corrosion

Semiconductors are materials with electrical conductivity between that of conductors and insulators
Characteristics of semiconductors:
- Electrical conductivity: semiconductors can be doped to increase or decrease conductivity
- Temperature dependence: semiconductor conductivity changes with temperature
- Applications: semiconductors are used in electronic devices, solar cells, and transistors

Packing efficiency is the percentage of space occupied by atoms in a crystal lattice
Types of packing:
- Cubic packing: atoms are arranged in a cubic pattern
- Hexagonal packing: atoms are arranged in a hexagonal pattern
- Face-centered cubic (FCC) packing: atoms are arranged in a cubic pattern with an atom at the center of each face
- Body-centered cubic (BCC) packing: atoms are arranged in a cubic pattern with an atom at the center of each cube
- Packing efficiency ranges: 52% (BCC) to 74% (FCC)

A crystal lattice is a three-dimensional arrangement of atoms, ions, or molecules in a repeating pattern
A unit cell is the smallest three-dimensional unit that repeats to form the crystal lattice
Lattice parameters include the dimensions of the unit cell (a, b, c, α, β, γ)
Crystal systems describe the symmetry of the lattice (e.g. cubic, tetragonal, orthorhombic, etc.)

Metallic bonding occurs between metal atoms in a crystal lattice
Delocalization of electrons allows them to move freely throughout the lattice
The resulting "sea of electrons" surrounds the metal ions
This leads to high electrical conductivity due to the mobility of electrons
Metallic bonding also gives rise to malleability and ductility, as metal atoms can be easily deformed without breaking

Semiconductors have electrical conductivity between that of conductors and insulators
Their conductivity can be increased or decreased by doping
The conductivity of semiconductors is temperature-dependent
Applications of semiconductors include electronic devices, solar cells, and transistors

Packing efficiency is the percentage of space occupied by atoms in a crystal lattice
Cubic packing, hexagonal packing, face-centered cubic (FCC) packing, and body-centered cubic (BCC) packing are types of packing arrangements
FCC packing has the highest packing efficiency at 74%, while BCC packing has the lowest at 52%