Magnesium Element Properties
Complete reference for Magnesium (Mg, element 12): atomic data, electron configuration, isotopes, physical constants, and unit converter.
Magnesium
Alkaline Earth Metal — Period 3, Group 2
Atomic Identity
Periodic Table Locator — Period 3 Neighborhood
Magnesium (Z=12) sits between sodium (alkali metal) and aluminum (post-transition metal) in Period 3. It is directly below beryllium (Z=4) and above calcium (Z=20) in Group 2.
Electron Configuration
No unpaired electrons — all orbitals filled
Key Isotopes of Magnesium
| Isotope | Symbol | Protons | Neutrons | Mass (u) | Natural Abundance | Stability |
|---|---|---|---|---|---|---|
| Magnesium-23 | ²³Mg | 12 | 11 | 22.9941242 | Radioactive |
Unstable
β⁺ decay, t½ = 11.317 s |
| Magnesium-24 | ²⁴Mg | 12 | 12 | 23.9850417 | 78.99% | Stable |
| Magnesium-25 | ²⁵Mg | 12 | 13 | 24.9858370 | 10.00% | Stable |
| Magnesium-26 | ²⁶Mg | 12 | 14 | 25.9825930 | 11.01% | Stable |
| Magnesium-27 | ²⁷Mg | 12 | 15 | 26.9843407 | Radioactive |
Unstable
β⁻ decay, t½ = 9.458 min |
| Magnesium-28 | ²⁸Mg | 12 | 16 | 27.9838768 | Radioactive |
Unstable
β⁻ decay, t½ = 20.915 hr |
Magnesium has three stable isotopes (Mg-24, Mg-25, Mg-26). Mg-26 is used in geochemistry to trace magnesium cycling; Mg-28 is used in medical research as a tracer isotope.
Physical Properties
Chemical Properties
Ground State Quantum Numbers
Notable Emission Lines
Magnesium produces a brilliant white flame. Its emission spectrum shows prominent lines in the UV and green regions; the 285.21 nm line is widely used in atomic absorption spectroscopy for magnesium analysis.
Property Unit Converter
Convert common Magnesium property values between units. Enter a value and select the conversion.
Common Magnesium Compounds
| Compound | Formula | Common Name | Key Uses |
|---|---|---|---|
| Magnesium oxide | MgO | Magnesia / periclase | Refractory materials, antacid, nutritional supplement, fertilizer |
| Magnesium hydroxide | Mg(OH)₂ | Milk of magnesia | Antacid, laxative, wastewater treatment, fire retardant |
| Magnesium sulfate | MgSO₄ | Epsom salt | Muscle relaxant baths, fertilizer, laxative, dyeing textiles |
| Magnesium chloride | MgCl₂ | Magnesium chloride | De-icing roads, dust control, food additive (tofu coagulant) |
| Magnesium carbonate | MgCO₃ | Magnesite | Refractory bricks, antacid, chalk substitute for gymnastics |
| Magnesium nitrate | Mg(NO₃)₂ | Magnesium nitrate | Fertilizers, pyrotechnics, catalyst, desiccant |
| Magnesium silicate | Mg₂SiO₄ | Forsterite / talc | Ceramics, insulation, cosmetics (talcum powder) |
| Chlorophyll | C₅₅H₇₂MgN₄O₅ | Chlorophyll a | Photosynthesis pigment in all green plants and algae |
Key Facts About Magnesium
Chlorophyll Central Atom
Every molecule of chlorophyll — the pigment powering photosynthesis in all green plants and algae — has a single Mg²⁺ ion at its center, chelated by a porphyrin ring. Without magnesium, plants cannot synthesize chlorophyll and eventually turn yellow, a symptom known as chlorosis.
Burns in CO₂ and N₂
Magnesium is one of the few elements that burns in carbon dioxide (Mg + CO₂ → MgO + C) and nitrogen (3 Mg + N₂ → Mg₃N₂). This makes standard CO₂ fire extinguishers ineffective and even dangerous on magnesium fires. Class D extinguishers using dry sand or special powder must be used instead.
Lightest Structural Metal
At 1.738 g/cm³, magnesium is the lightest structural metal used in engineering — about 35% lighter than aluminum and 78% lighter than iron. Magnesium alloys are extensively used in aerospace, automotive, and consumer electronics for weight-critical components.
Essential Biological Role
Magnesium is the fourth most abundant mineral in the human body and is required by over 300 enzyme systems. It is critical for ATP synthesis (all ATP in cells is complexed as Mg-ATP), DNA and RNA synthesis, protein synthesis, and regulation of nerve and muscle function.
Eighth Most Abundant
Magnesium is the eighth most abundant element in Earth's crust (~2.1% by mass). It is the third most abundant element dissolved in seawater (~1272 mg/L). Major mineral sources include magnesite (MgCO₃), dolomite (CaMg(CO₃)₂), and olivine (Mg₂SiO₄).
History and Name
Magnesium was recognized as an element by Joseph Black in 1755. Humphry Davy first isolated magnesium metal in 1808 by electrolysis. The name derives from Magnesia, a region of Greece (modern Thessaly) where magnesium-containing minerals were found; it shares this etymology with manganese and magnet.
Summary
Complete reference for Magnesium (Mg, element 12): atomic data, electron configuration, isotopes, physical constants, and unit converter.
How it works
- Browse the atomic identity section for symbol, atomic number, and standard atomic weight.
- Check the electron configuration panel for orbital notation and quantum numbers.
- Review the isotopes table for stable and notable radioactive isotopes including natural abundances.
- Consult the physical and chemical properties panels for melting point, density, ionization energies, and more.
- Use the interactive unit converter to convert magnesium property values between common units.
- Explore the mini periodic table locator to visualize where magnesium sits among neighboring elements.
Use cases
- Look up magnesium constants for chemistry homework or exams.
- Verify atomic data when writing lab reports or research papers.
- Reference isotope data for nuclear chemistry or geochronology research.
- Convert melting/boiling points between Celsius, Fahrenheit, and Kelvin.
- Teach or learn alkaline earth metal properties using magnesium as a prime example.
- Confirm electron configuration before writing molecular orbital or Lewis dot diagrams.
- Research magnesium compounds for pharmaceutical, industrial, or materials science work.
- Quick-reference ionization energies for electrochemistry or spectroscopy calculations.