Structure
Not a diagram of dots on rings — a Monte-Carlo sample of the actual probability density |ψ|² for each occupied subshell. Drag to rotate. Blue and violet mark opposite signs of the wavefunction, which is what makes bonding possible.
Measured values
Every bar shows where magnesium sits among all 118 elements for that property.
Sources: IUPAC 2021 standard atomic weights · CRC Handbook of Chemistry and Physics · NIST. Values marked ~ are predicted rather than measured.
Size, to scale
Radius 160 pm — that is 0.16 nm, so about 3125 million of them side by side would span a millimetre.
Thermal range
Magnesium is liquid over a 440 K window, from 923 K to 1363 K.
The story
Light, strong metal. Essential for chlorophyll and hundreds of enzymes.
The discovery of magnesium in 1808 followed directly from Humphry Davy's significant success with sodium and potassium the previous year. Fresh from his electrolytic triumphs that had earned him international acclaim, Davy systematically targeted other alkaline earth compounds that might yield new metallic elements. Magnesia alba (magnesium oxide), known since ancient times for its medicinal properties, became his next target.
Davy had learned from his sodium experiments that water interfered with electrolysis, so he prepared barely moistened magnesium oxide mixed with mercury oxide to increase conductivity. Using his powerful 600-plate battery—the advanced electrical apparatus of its era—Davy applied current to the mixture on October 9, 1808, exactly one year and three days after discovering sodium.
Unlike the dramatic immediate success with sodium, magnesium proved frustratingly elusive. Davy's early experiments produced only tiny specks of an amalgam (mercury alloy) that seemed to contain a new metal, but isolating pure magnesium required techniques beyond early 19th-century capabilities. The metal's high reactivity and strong affinity for oxygen made separation from mercury extremely difficult.
Davy presented his preliminary results to the Royal Society, announcing he had "obtained distinct evidence of the existence of a new metal" but acknowledged his inability to isolate it in pure form. This honest admission of partial success demonstrated the rigorous scientific standards that made Davy's work so respected throughout Europe, even as Napoleon's armies battled British forces.
The first isolation of pure magnesium metal came in 1831 through the brilliant work of French chemist Antoine Alexandre Brutus Bussy at the École Polytechnique in Paris. Bussy developed an ingenious chemical reduction method, heating anhydrous magnesium chloride with metallic potassium in a platinum crucible at red heat: MgCl₂ + 2K → Mg + 2KCl.
Bussy's success required overcoming multiple technical challenges. He had to prepare perfectly anhydrous magnesium chloride (any water would ruin the reaction), obtain pure potassium metal (still expensive and difficult to produce), and perform the reaction in an inert atmosphere to prevent immediate oxidation of the product. His platinum equipment, while costly, proved essential for withstanding the reaction's high temperatures.
Michael Faraday, Davy's former assistant who had become the Royal Institution's leading scientist, made crucial contributions to understanding magnesium's properties in the 1830s. Faraday used his newly developed laws of electrolysis to determine magnesium's atomic weight and establish its position among the alkaline earth metals.
Faraday's systematic experiments revealed magnesium's remarkable properties: its brilliant white flame, its ability to burn in carbon dioxide (producing carbon and magnesium oxide), and its strong reducing power. These characteristics would later prove crucial for magnesium's applications in photography, pyrotechnics, and metallurgy.
Commercial magnesium production remained impractical until 1886, when German chemists Robert Bunsen and Augustus Matthiessen developed electrolytic methods for producing magnesium from molten chloride salts. Their process, refined over decades, enabled large-scale production that made magnesium affordable for industrial applications.
World War I dramatically accelerated magnesium development as military needs for lightweight materials and incendiary devices drove innovation. The British and German governments invested heavily in magnesium production capacity, leading to the first magnesium alloy aircraft components and the devastating effectiveness of magnesium incendiary bombs during the London Blitz.
Perhaps the most profound discovery about magnesium came in 1906 when German chemist Richard Willstätter proved that chlorophyll molecules contain magnesium at their centers. This revelation explained why plants deprived of magnesium develop chlorosis (yellowing) and established magnesium's fundamental role in photosynthesis—the process that sustains virtually all life on Earth.
Willstätter's work, which earned him the 1915 Nobel Prize in Chemistry, demonstrated that magnesium's perfect size and charge enable it to coordinate with chlorophyll's porphyrin ring while remaining labile enough for the rapid electron transfers required in photosynthesis. This discovery linked magnesium's cosmic abundance to life's fundamental chemistry, showing how stellar nucleosynthesis created the elements essential for biological complexity.
Applications
Magnesium alloys revolutionized aerospace design through their exceptional strength-to-weight ratio, being 35% lighter than aluminum while maintaining comparable strength. The AZ91D alloy (9% aluminum, 1% zinc) achieves tensile strengths of 250 MPa while weighing only 1.81 g/cm³, making it ideal for aircraft engine housings, transmission cases, and structural components.
Modern helicopters extensively use magnesium alloy gearboxes and rotor hubs where weight reduction directly improves payload capacity and fuel efficiency. The Sikorsky UH-60 Black Hawk helicopter incorporates over 800 pounds of magnesium components, primarily in the main gearbox housing. Space applications include satellite structures and rocket engine components where every gram matters for orbital missions.
Automotive manufacturers increasingly adopt magnesium die-casting for engine blocks, transmission housings, and seat frames to meet fuel efficiency standards. BMW's N52 engine incorporates a magnesium-aluminum composite crankcase that reduces engine weight by 10 kg compared to iron alternatives, improving fuel economy by 3-5%.
Magnesium steering wheels provide better shock absorption and reduce driver fatigue during long journeys. The trend toward electric vehicles accelerates magnesium adoption, as lighter vehicles extend battery range. Tesla's Model S uses magnesium components in the dashboard support structure and seat frames, contributing to the vehicle's impressive efficiency ratings.
Consumer electronics leverage magnesium's electromagnetic shielding properties and heat dissipation capabilities. Laptop computers use magnesium alloy housings that provide 75% better heat conduction than plastic alternatives while offering superior electromagnetic interference (EMI) protection for sensitive components.
Professional cameras like the Canon EOS-1D series employ magnesium alloy bodies for durability and weather sealing. The material's excellent machinability allows complex geometries for lens mounts and internal structural components. Smartphone manufacturers increasingly use magnesium alloys for internal frames, providing structural integrity while minimizing weight impact on battery life.
Magnesium's brilliant white combustion (3,100°C) makes it essential for military flares, emergency signaling devices, and photographic flash powder. Marine distress flares burn magnesium-strontium mixtures that produce intense red light visible for miles, while aircraft ejection seat flares use pure magnesium for maximum illumination intensity.
Thermite welding applications use magnesium powder as an ignition source for iron oxide-aluminum mixtures, reaching temperatures sufficient to weld railroad tracks. The exothermic reaction: 3Mg + Fe₂O₃ → 3MgO + 2Fe generates enough heat to melt steel, making field repairs possible in remote locations.
Magnesium serves as a powerful reducing agent for producing specialty metals including titanium, zirconium, hafnium, and uranium. The Pidgeon process reduces magnesium oxide with ferrosilicon at 1,200°C under vacuum, producing 80% of global magnesium supply. This process requires precise temperature control and inert atmosphere to prevent oxidation.
Spheroidal graphite iron (ductile iron) production relies on magnesium additions to transform graphite flakes into spherical nodules, dramatically improving mechanical properties. Adding 0.03-0.08% magnesium to molten iron creates ductile iron with tensile strengths exceeding 700 MPa, used in automotive crankshafts, pipes, and heavy machinery components.
Magnesium compounds play crucial roles in pharmaceutical manufacturing and medical treatments. Magnesium stearate serves as a lubricant in tablet manufacturing, preventing ingredients from sticking to equipment while ensuring consistent tablet weight and dissolution rates. Over 95% of pharmaceutical tablets contain magnesium stearate.
Biodegradable magnesium implants represent significant medical technology for orthopedic applications. These implants gradually dissolve in body fluids, eliminating the need for surgical removal while promoting bone healing. Magnesium's biocompatibility and mechanical properties similar to human bone make it ideal for temporary fixation devices, stents, and surgical screws.
Where it comes from
23300 mg/kg of Earth's crust · more abundant than 95% of elements
Magnesium ranks as the eighth most abundant element in Earth's crust at 2.3% by weight and the third most abundant in seawater at 1,290 parts per million. This abundance reflects magnesium's role as a primary component of Earth's mantle, where olivine ((Mg,Fe)₂SiO₄) and pyroxene minerals dominate the upper 400 kilometers of our planet's interior.
The concentration gradient from Earth's core (virtually no magnesium) through the silicate mantle (25% magnesium) to the crustal rocks demonstrates how planetary differentiation concentrated lighter elements in outer layers. Magnesium's ionic radius (0.72 Å) and charge (+2) make it ideally suited for octahedral coordination in silicate minerals.
Olivine, the most abundant magnesium-bearing mineral, forms when magnesium-rich magmas crystallize at high temperatures (1,200-1,800°C). Major olivine deposits in Norway's Åheim complex and North Carolina's Buck Creek provide industrial-grade magnesium sources. These deposits formed from ultramafic intrusions rich in primitive mantle compositions.
Evaporite deposits represent another crucial magnesium source, particularly the Zechstein Basin underlying Northern Europe and the Permian Basin in Texas. These deposits formed 250 million years ago when restricted sea basins evaporated, concentrating magnesium chloride and sulfate to saturation levels. Modern extraction from the Dead Sea and Great Salt Lake continues this natural concentration process.
Seawater contains 53 million tons of magnesium per cubic kilometer, maintained through complex biogeochemical cycles involving river input, hydrothermal circulation, and biological uptake. Mid-ocean ridge hydrothermal systems continuously exchange magnesium between seawater and hot basaltic rocks, maintaining oceanic magnesium concentrations over geological time.
Marine organisms extensively utilize magnesium in biomineralization processes. Coralline algae and foraminifera incorporate magnesium into calcium carbonate structures, creating high-magnesium calcite that records ancient ocean chemistry. These biological processes remove significant magnesium from seawater while creating vast limestone deposits enriched in magnesium.
Magnesium forms through carbon burning in massive stars (>8 solar masses) when core temperatures exceed 600 million Kelvin. The primary reaction pathway involves carbon-12 nuclei fusing to form neon-20, which then captures alpha particles to produce magnesium-24, the most abundant magnesium isotope (79% of natural magnesium).
Type II supernovae explosively synthesize magnesium through oxygen burning processes, where oxygen-16 nuclei undergo rapid fusion reactions at temperatures exceeding 1.5 billion Kelvin. These stellar explosions disperse magnesium throughout galaxies, enriching the interstellar medium that forms subsequent generations of stars and planets.
Chlorophyll molecules contain magnesium at their centers, making photosynthesis impossible without this element. Each chlorophyll molecule coordinates one magnesium ion with four nitrogen atoms in a porphyrin ring structure, enabling light absorption at specific wavelengths (430 nm and 662 nm for chlorophyll a).
Human physiology requires 400-420 mg of daily magnesium for over 300 enzymatic reactions, including ATP synthesis, protein synthesis, and muscle contraction. Magnesium deficiency affects 10-30% of the global population, causing muscle cramps, irregular heartbeat, and increased osteoporosis risk. Green leafy vegetables, nuts, and whole grains provide the richest dietary sources.
The Pidgeon process dominates global magnesium production, reducing dolomite (CaMg(CO₃)₂) with ferrosilicon at 1,200°C under vacuum: 2MgO + 2CaO + FeSi → 2Mg + Ca₂SiO₄ + Fe. This process, developed in Canada during World War II, produces 80% of the world's magnesium metal, primarily in China which accounts for 87% of global production.
Electrolytic extraction from seawater provides an alternative route, particularly in areas with abundant cheap electricity. The Dow process extracts magnesium hydroxide from seawater using lime, then converts it to magnesium chloride for electrolysis. This renewable approach could theoretically supply unlimited magnesium, as seawater contains over 4 billion years' worth at current consumption rates.
Handling
Extreme Fire Risk: Magnesium metal burns with intense white light at 3,100°C, producing temperatures hot enough to melt steel. Magnesium fires cannot be extinguished with water (which decomposes to form explosive hydrogen), carbon dioxide, or standard chemical extinguishers. Use Class D fire extinguishers containing sodium chloride, graphite, or specialized magnesium fire suppression powders.
Powder Hazards: Finely divided magnesium presents severe explosion risks with minimum ignition energy of only 40 millijoules. Magnesium dust clouds can explode when concentrations exceed 0.02 oz/ft³. Maintain humidity above 65% to reduce static electricity accumulation and ensure proper grounding of all equipment handling magnesium powder.
Metal Fume Fever: Inhaling magnesium oxide fumes causes metal fume fever with symptoms including chills, fever, nausea, and difficulty breathing appearing 4-12 hours after exposure. While not permanently harmful, symptoms can persist for 24-48 hours. OSHA permissible exposure limit is 15 mg/m³ for magnesium oxide fumes.
Respiratory Protection: Use NIOSH-approved respirators with P100 filters when magnesium dust or fumes may be present. Provide local exhaust ventilation maintaining capture velocities of 100-200 feet per minute at dust generation points.
Essential Nutrient: Adults require 400-420 mg daily magnesium for proper physiological function. Deficiency symptoms include muscle cramps, irregular heartbeat, personality changes, and increased osteoporosis risk. However, excessive supplementation (>5,000 mg daily) can cause diarrhea, nausea, and abdominal cramping.
Drug Interactions: Magnesium supplements can interfere with antibiotic absorption (tetracycline, quinolones) and may enhance effects of blood pressure medications. Consult healthcare providers before taking magnesium supplements with prescription medications.
Personal Protective Equipment: Safety glasses with side shields, flame-resistant clothing, leather gloves for handling solid magnesium. Avoid synthetic fabrics that may melt and adhere to skin during flash fires.
Storage Requirements: Store magnesium in cool, dry areas away from oxidizers, acids, and water sources. Use airtight containers with desiccants for magnesium powder. Maintain storage temperatures below 30°C to prevent spontaneous combustion of fine powders.
Static Electricity Control: Ground all equipment, use conductive containers, maintain relative humidity above 65%, and eliminate ignition sources when handling magnesium powder or machining magnesium alloys.
Magnesium Fires: Evacuate area immediately, call fire department specifying "magnesium metal fire," and do not attempt suppression unless trained with proper Class D extinguishing agents. Allow small fires to burn out while protecting surrounding materials with thermal barriers.
Skin/Eye Contact: Remove magnesium particles carefully without rubbing (to prevent embedded fragments), flush with copious water for 15+ minutes, and seek medical attention for any burns or embedded metal particles. Remove contact lenses if easily removable.
Inhalation Exposure: Move victim to fresh air immediately, monitor for delayed onset metal fume fever symptoms, provide supplemental oxygen if available, and seek medical evaluation for significant exposures. Symptoms may not appear for several hours.
Ingestion: Do not induce vomiting. Rinse mouth with water, give small amounts of water if conscious, and seek immediate medical attention. Large quantities of metallic magnesium can react with stomach acid, producing hydrogen gas.
Quick answers
Magnesium (symbol Mg) is element 12 on the periodic table, a alkaline earth metal in period 3, group 2. The metal at the centre of chlorophyll — and the one that burns with a light bright enough to blind a camera. At room temperature it is a solid.
[Ne] 3s², giving 3 occupied shells holding 2, 8, 2 electrons respectively.Magnesium melts at 923 K (649.9 °C) and boils at 1363 K (1089.9 °C).
The standard atomic weight of Magnesium is 24.305 u. That is a weighted average across its naturally occurring isotopes, which is why it is rarely a whole number.
Magnesium has a density of 1.738 g/cm³. Water is 1.0 g/cm³, so a block of magnesium is about 1.7× heavier.
Magnesium has a Pauling electronegativity of 1.31. The scale runs from 0.70 (francium, the least greedy for electrons) to 3.98 (fluorine, the most). Values in this middle band tend to form covalent rather than strongly ionic bonds.
Magnesium was discovered in 1755 by Joseph Black. It is named after magnesia, a district of Thessaly.
Magnesium makes up about 2.33% of the Earth's crust — one of the most abundant elements there is.