Metallic crystals
Introduction
Metallic crystals are a type of crystal structure that is formed by metallic bonds. These bonds are characterized by a sea of shared electrons that move freely around positive metal ions, creating a strong bond that is both conductive and malleable. Metallic crystals are prevalent in many of the materials we use daily, from the aluminum in our cars to the copper in our electrical wires.
Structure of Metallic Crystals
The structure of metallic crystals is defined by the arrangement of atoms within the crystal. In metallic crystals, the atoms are arranged in a tightly packed, repeating pattern that extends in all three spatial dimensions. This pattern is known as a crystal lattice, and it is the defining characteristic of a crystal structure.
There are four main types of lattices in metallic crystals: simple cubic, body-centered cubic, face-centered cubic, and hexagonal close-packed. Each of these lattice types is characterized by a different arrangement of atoms within the unit cell, which is the smallest repeating unit of the lattice.
Simple Cubic Lattice
In a simple cubic lattice, each atom is surrounded by eight others, positioned at the corners of a cube. This is the simplest type of lattice, and it is not very common in metallic crystals due to its low packing efficiency.
Body-Centered Cubic Lattice
A body-centered cubic lattice has an additional atom located in the center of the cube. This atom is surrounded by eight others at the corners of the cube, resulting in a higher packing efficiency than the simple cubic lattice. Metals such as iron, chromium, and tungsten have a body-centered cubic structure.
Face-Centered Cubic Lattice
In a face-centered cubic lattice, there are atoms at the corners of the cube and in the center of each face. This results in each atom being surrounded by twelve others, providing the highest packing efficiency of the cubic lattices. Many common metals, including aluminum, copper, and silver, have a face-centered cubic structure.
Hexagonal Close-Packed Lattice
The hexagonal close-packed lattice is characterized by a hexagonal arrangement of atoms, with additional atoms filling the gaps between the layers. This structure is common in metals such as magnesium and zinc.
Properties of Metallic Crystals
Due to the unique structure and bonding of metallic crystals, they exhibit a number of distinctive properties. These include high electrical and thermal conductivity, malleability, ductility, and a shiny appearance.
Electrical Conductivity
Metallic crystals are excellent conductors of electricity. This is due to the sea of electrons that exists within the crystal structure. These electrons are not bound to any particular atom and can move freely throughout the crystal, allowing for the easy flow of electric current.
Thermal Conductivity
Similarly, metallic crystals are also good conductors of heat. The free electrons within the crystal structure can absorb and transfer heat energy, allowing for efficient heat conduction.
Malleability and Ductility
Metallic crystals are malleable, meaning they can be hammered or pressed into thin sheets without breaking. They are also ductile, which means they can be drawn into thin wires. These properties are a result of the metallic bonds that allow atoms to slide past each other without breaking the bond.
Appearance
Metallic crystals have a characteristic shiny appearance, known as metallic luster. This is due to the free electrons within the crystal structure, which reflect light and give the metal its shiny appearance.
Applications of Metallic Crystals
Metallic crystals are used in a wide range of applications, due to their unique properties. They are used in the construction of buildings and vehicles, in electrical wiring and electronics, and in the manufacture of a wide range of consumer goods.