Periodic table › Magnesium
1. Identity and classification
Silvery-white, lustrous, moderately soft metallic solid
- Name and symbol
- Magnesium (Magnesium) · Mg
- Atomic number
- 12
- Relative atomic weight / mass number
- 24.305 ± 0.002
- Group · period · block
- 2 · 3 · s
- Category
- Alkaline Earth Metal
- State near room temperature
- Solid
- Stable isotopes
- At least one stable isotope
- CAS number
- 7439-95-4
Square brackets [A] indicate a representative isotope mass number, not an average atomic weight. Neutron counts differ between isotopes.
2. Atomic structure and electron configuration
- Protons · electrons in a neutral atom
- 12 · 12
- Neutrons in reference isotope
- 12 (24Mg)
- Full electron configuration
1s² 2s² 2p⁶ 3s²- Abbreviated configuration
[Ne]3s²- Electrons per shell
- 2, 8, 2
- Listed oxidation states
- +2
- Electronegativity
- 1.31 (Pauling)
- First ionization energy
- 737.727 kJ/mol · 7.646 eV
- Electron affinity
- Not established
- Covalent radius
- 141 pm
- van der Waals radius
- 173 pm
Configurations of superheavy elements may include theoretical predictions. Different definitions of atomic radius are not interchangeable.
3. Physical and thermal properties
- Density
- 1.74 g/cm³
- Melting point
- 923 K · 649.85 °C · 1201.73 °F
- Boiling point
- 1363 K · 1089.85 °C · 1993.73 °F
- Crystal structure
- HCP
- Specific heat
- 1.023 J/(g·K)
- Thermal conductivity
- 156 W/(m·K)
- Enthalpy of fusion
- 8.48 kJ/mol
- Enthalpy of vaporization
- 128 kJ/mol
- Magnetic ordering
- Paramagnetic
- Mohs hardness
- 2.5
- Speed of sound
- 4940 m/s
Density and structure depend on temperature, pressure and allotrope. 25°C is a room-temperature reference, not STP. Unestablished values are not zero.
4. Chemical behavior and compounds
The +2 oxidation state is common; beryllium compounds show substantial covalent character.
Selected compounds: MgO / Mg₂O₃ (Oxide) · MgClₙ (Chloride) · MgFₙ (Fluoride)
Reaction reference
Oxide layers form in air; the behavior depends on temperature and the metal.
Reactivity with water increases broadly down Group 2; beryllium and magnesium differ from the heavier members.
5. Isotopes
| Isotope | Status | Natural abundance | Half-life |
|---|---|---|---|
| 24Mg | Stable | 78.965% | Stable |
| 25Mg | Stable | 10.011% | Stable |
| 26Mg | Stable | 11.025% | Stable |
Half-life units: s seconds, m minutes, h hours, d days, Y years. A dash means no natural-abundance value is given, not zero. Listed records are selected ground states; metastable states are distinct.
6. Discovery and occurrence
- Discovery
- 1808 CE
- Scientists associated with discovery
- Joseph Black & Humphry Davy
- Location
- Scotland / England
- Origin
- Natural
- Listed crustal abundance
- Not established
Minerals and naming reference
Magnesite (MgCO₃), Dolomite, Carnallite, Brucite, Seawater
Named from scientific/historical roots associated with Magnesium (Mg), discovered or characterized by Joseph Black & Humphry Davy.
7. Applications
Lightweight automotive & aerospace alloys, chlorophyll central atom in plants, antacids & Epsom salts, fireworks
Detailed applications by field
- everyday
- Lightweight automotive & aerospace alloys, chlorophyll central atom in plants, antacids & Epsom salts, fireworks
- industry
- Used in alkaline earth metal processing, specialized alloys, and chemical manufacturing (Lightweight automotive & aerospace alloys, chlorophyll central atom in plants, antacids & Epsom salts, fireworks).
- electronics
- Applied in electronic components, semiconductors, or functional coatings where Magnesium's electronic structure ([Ne] 3s²) provides target conductivity.
- medicine
- Diagnostic imaging, biomedical instrumentation, or pharmaceutical synthesis research.
- energy
- Utilized in power generation, battery materials, catalysts, or nuclear technology involving Magnesium.
- aerospace
- High-performance materials, structural alloys, or space instrumentation utilizing Magnesium.
- agriculture
- Soil geochemistry analysis, trace micronutrient research, or analytical environmental monitoring.
- science
- Spectroscopic standard, crystallography, and quantum chemistry studies of Period 3 s-block elements.
8. Biological role and safety
Hazard depends on the isotope, chemical form, dose and exposure route.
Elemental substances, ions, compounds and radioisotopes can have different health effects. This is an educational reference; laboratory work requires the material safety data sheet and trained supervision.
Biological role reference
Classified as essential in human and biological systems.