Quick Facts
| Property | Value |
|---|---|
| Symbol | Mg |
| Atomic Number | 12 |
| Atomic Mass | 24.305 u |
| Category | Alkaline Earth Metal |
| Period | 3 |
| Group | 2 |
| Block | s |
| Electron Configuration | [Ne] 3s² |
Physical Properties
| Property | Value |
|---|---|
| State at 20°C | Solid |
| Density | 1.738 g/cm³ |
| Melting Point | 650°C (923 K) |
| Boiling Point | 1090°C (1363 K) |
| Appearance | Shiny gray solid |
Atomic Properties
| Property | Value |
|---|---|
| Electron Configuration | [Ne] 3s² |
| Electronegativity | 1.31 (Pauling scale) |
| First Ionization Energy | 737.7 kJ/mol |
| Atomic Radius | 160 pm |
| Covalent Radius | 141 pm |
| Van der Waals Radius | 173 pm |
History and Discovery
Discovered by: Joseph Black (recognized), Humphry Davy (isolated) Year of Discovery: 1755 (recognized), 1808 (isolated) Location: Edinburgh, Scotland and London, England
Etymology
The name "magnesium" comes from Magnesia, a district in Thessaly, Greece, where the mineral magnesite was found. The area gave its name to both magnesium and manganese.
Discovery Story
Joseph Black recognized magnesium as an element in 1755 by distinguishing magnesia (magnesium oxide) from lime (calcium oxide). Humphry Davy isolated magnesium metal in 1808 through electrolysis of a mixture of magnesia and mercuric oxide. Antoine Bussy produced larger quantities in 1831 by heating magnesium chloride with potassium.
Isotopes
| Isotope | Natural Abundance | Half-life | Decay Mode |
|---|---|---|---|
| ²⁴Mg | 78.99% | Stable | - |
| ²⁵Mg | 10.00% | Stable | - |
| ²⁶Mg | 11.01% | Stable | - |
Occurrence
Natural Abundance
Magnesium is the eighth most abundant element in Earth's crust (about 2.1%) and the third most abundant element dissolved in seawater. It is never found free in nature. Major sources include magnesite (MgCO₃), dolomite (CaMg(CO₃)₂), and carnallite (KMgCl₃·6H₂O).
Extraction and Production
- Electrolysis: Of molten magnesium chloride (Dow process)
- Pidgeon Process: Thermal reduction of magnesium oxide with silicon
- Seawater Extraction: Precipitation as magnesium hydroxide
- Global production: about 1 million tons annually
Applications and Uses
Industrial Applications
- Aluminum alloys (improves strength and corrosion resistance)
- Die-casting for automotive parts
- Desulfurization of steel
- Sacrificial anodes (cathodic protection)
Aerospace Applications
- Lightweight structural components
- Aircraft wheels and engine parts
- Missile and rocket components
Chemical Applications
- Grignard reagents in organic synthesis
- Reducing agent in metal production
- Fireworks and flares (bright white flame)
Other Uses
- Antacids (magnesium hydroxide, "milk of magnesia")
- Epsom salts (magnesium sulfate)
- Chlorophyll (central magnesium atom)
- Fire starters and survival tools
Biological Role
Magnesium is essential for life. It is involved in over 300 enzymatic reactions including energy production, DNA synthesis, and muscle function.
In the Human Body
- About 25 g in adult body (60% in bones)
- Essential cofactor for ATP-related enzymes
- Required for protein synthesis and DNA replication
- Important for muscle and nerve function
- Daily requirement: 300-400 mg
Dietary Sources
Green leafy vegetables (chlorophyll), nuts, seeds, whole grains, and dark chocolate are rich in magnesium.
Safety and Hazards
Toxicity
Magnesium is non-toxic at normal levels. Excess can cause diarrhea (magnesium salts are laxatives). Hypermagnesemia is rare but can occur with kidney impairment.
Handling Precautions
- Magnesium ribbon and powder ignite easily and burn with intense white light
- Burning magnesium is extremely difficult to extinguish (reacts with water, CO₂, and nitrogen)
- Use class D fire extinguisher or dry sand
- Magnesium fires can cause severe eye damage from UV radiation
- Magnesium shavings present fire and explosion hazard
Environmental Impact
Magnesium is naturally abundant and environmentally benign. Mining and processing have typical industrial environmental impacts.
Interesting Facts
- Magnesium burns with a brilliant white light that was used in early photography flash
- It is the lightest structural metal used in engineering
- Chlorophyll, the pigment that makes plants green, has a magnesium atom at its center
- Magnesium-aluminum alloys are used in laptop cases and camera bodies
- The element is so light it floats on water (though it reacts with it)