Magnesium
Mg
Description
Magnesium (Mg) is a lightweight, silvery-white alkaline earth metal. It is the eighth most abundant element in the Earth's crust and the third most abundant element dissolved in seawater. Known primarily as the lightest structural metal, magnesium is prized in engineering for its exceptional strength-to-weight ratio and its high chemical reactivity, which makes it essential for both biological life and industrial metallurgy.
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Crystallographic Structure
For material science and 3D lattice modeling, magnesium is the definitive example of the Hexagonal Close-Packed (HCP) structure. Unlike the more ductile FCC metals like Gold or Copper, the HCP structure of magnesium provides fewer slip planes, which influences how the metal is machined and formed.
- Crystal System: Hexagonal
- Lattice Parameters: a = 3.209$ Å, c = 5.211 Å
- c/a Ratio: 1.623 (Very close to the ideal ratio of 1.633)
- Coordination Number: 12
- Atomic Packing Factor (APF): 0.74
- Symmetry Group: $P6_3/mmc$
Properties
Magnesium's most striking physical characteristic is its density; it is approximately 33% lighter than aluminum and 75% lighter than steel, making it the material of choice for weight-sensitive applications.
- Atomic Number: 12
- Atomic Mass: 24.305 u
- Melting Point: 650°C
- Boiling Point: 1,091°C
- Density: $1.738\text{ g/cm}^3$
- Flame Color: Produces a brilliant, blinding white light when burned (used in flares and pyrotechnics)
Applications
- Automotive & Aerospace: Used for engine blocks, steering wheels, gearbox casings, and airframes to reduce vehicle weight and improve fuel efficiency.
- Electronics: The preferred material for the chassis of high-end laptops, cameras, and mobile phones due to its durability and lightness.
- Alloying Agent: More than 40% of all magnesium produced is used as an alloying element for aluminum to improve its hardness and corrosion resistance.
- Sacrificial Anodes: Used to protect underground tanks, pipelines, and ship hulls from corrosion by "sacrificing" itself to oxidation instead of the steel structure.
- Health & Medicine: Essential for human biology (enzyme cofactor); commercially used in Epsom salts ($MgSO_4$) and antacids.
Unit Cell Axes
a=3.21 b=3.21 c=5.21
Unit Cell Angles
α=90° β=90° γ=120°
Lattice Type
Primitive
Grid Expansion
Appearance
Coordination