Magnesium (Mg)
Alkaline earth metal
Magnesium is a light, silvery metal that burns with a brilliant white flame. Two thirds lighter than steel, it is prized for lightweight alloys — and at the centre of every chlorophyll molecule, it helps plants capture sunlight.
Position on the periodic table
Atomic properties
| Atomic number | 12 |
|---|---|
| Atomic mass | 24.305 amu |
| Electron configuration | 1s2 2s2 2p6 3s2 |
| Noble gas shorthand | [Ne] 3s2 |
| Electrons per shell | 2, 8, 2 |
| Valence electrons (outer shell) | 2 |
| Common oxidation states | +2 |
| Electronegativity (Pauling) | 1.31 |
| Covalent radius (approx.) | 141 pm |
| First ionization energy | 737.7 kJ/mol |
| Electron affinity | -40 kJ/mol |
Physical properties
| State at 25 °C | Solid |
|---|---|
| Density | 1.738 g/cm³ |
| Melting point | 649.85 °C (923 K) |
| Boiling point | 1089.8 °C (1363 K) |
| Appearance | shiny grey solid |
| Radioactive | No |
| Origin | Occurs naturally |
Electron configuration of magnesium
Magnesium's ground-state electron configuration is 1s2 2s2 2p6 3s2, usually shortened to [Ne] 3s2. Its electrons occupy 3 shells (2, 8, 2), placing it in period 3 of the s-block. The 2 outer-shell electrons drive its bonding behaviour. Explore it interactively in the electron configuration calculator.
Uses of magnesium
- Lightweight alloys for cars, laptops and aircraft
- Fireworks and flares (bright white light)
- Antacids and laxatives (milk of magnesia)
- Sacrificial anodes that stop pipelines rusting
Biological role: Essential — hundreds of human enzymes need magnesium, and it sits at the heart of chlorophyll.
Occurrence: About 2.3% of the Earth's crust; the third most abundant dissolved element in seawater.
Common compounds of magnesium
MgO
Magnesium oxide
Mg(OH)2
Milk of magnesia
MgSO4
Epsom salt (magnesium sulfate)
History and discovery
Discovered: 1808 — Joseph Black. Name origin: From Magnesia, a district in Greece rich in magnesium minerals.
Recognised as an element by Joseph Black in 1755; Humphry Davy isolated an impure form in 1808.
Safety notes
Magnesium ribbon burns extremely brightly — never look directly at it, and never try to put out a magnesium fire with water.
Educational context only — always follow your school's laboratory rules and never handle chemicals without proper supervision. See our disclaimer.
Practice questions
Quick practice: Magnesium
1. What is the chemical symbol of Magnesium?
2. What is the atomic number of Magnesium?
3. Which category does Magnesium belong to?
4. What is the state of Magnesium at room temperature?
5. Which period of the periodic table is Magnesium in?
Magnesium FAQs
What is the atomic number of magnesium?
Magnesium's atomic number is 12 — every magnesium atom has 12 protons in its nucleus.
What is the symbol for magnesium?
Mg. From Magnesia, a district in Greece rich in magnesium minerals.
Is magnesium a metal, nonmetal, or metalloid?
Magnesium is classified as a alkaline earth metal.
What state is magnesium at room temperature?
At about 25 °C, magnesium is a solid. It melts at 649.85 °C.
How many valence electrons does magnesium have?
Magnesium has 2 electrons in its outer shell (shell pattern: 2, 8, 2).
What is magnesium used for?
Key uses include: lightweight alloys for cars, laptops and aircraft; fireworks and flares (bright white light); antacids and laxatives (milk of magnesia).
Related elements
Keep working with this element
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