Magnesium (Mg) – element 12
Magnesium is a chemical element with the symbol Mg and atomic number 12. It is a alkaline earth metal in group 2 (alkaline earth metals), period 3 of the periodic table (s-block), and is a solid at room temperature.
Magnesium (Mg) has atomic number 12, atomic mass 24.305 u and electron configuration [Ne] 3s2.
Magnesium facts
| Symbol | Mg |
|---|---|
| Atomic number | 12 |
| Atomic mass | 24.305 u (g/mol) |
| Category | alkaline earth metal |
| Group | group 2 (alkaline earth metals) |
| Period | 3 |
| Block | s-block |
| Phase at 20 °C | Solid |
| Electron configuration | 1s2 2s2 2p6 3s2 |
| Noble-gas notation | [Ne] 3s2 |
| Electrons per shell | 2, 8, 2 |
| Valence electrons | 2 |
Bohr model and shells
Magnesium has 12 electrons in 3 shells: 2, 8, 2. Full configuration and noble-gas notation are in the table; work out any element or ion with the electron configuration calculator.
Physical and atomic properties
| Melting point | 923 K (649.9 °C) |
|---|---|
| Boiling point | 1363 K (1089.8 °C) |
| Density | 1.738 g/cm³ |
| Electronegativity (Pauling) | 1.31 |
| Electron affinity | -40 kJ/mol |
| Ionization energies | 737.7, 1450.7, 7732.7 kJ/mol (1st, 2nd, 3rd) |
| Molar heat capacity | 24.869 J/(mol·K) |
| Discovered by | Joseph Black |
Use the atomic mass in the molar mass calculator for any formula containing Mg.
Position in the periodic table
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Frequently asked questions
What is the atomic mass of magnesium?
The atomic mass of magnesium is 24.305 u, so one mole of magnesium atoms weighs 24.305 g.
What is the electron configuration of magnesium?
Magnesium has 12 electrons: 1s² 2s² 2p⁶ 3s², or [Ne] 3s² in noble-gas notation. Electrons per shell: 2, 8, 2.
How many valence electrons does magnesium have?
Magnesium has 2 valence electrons (group 2).
Is magnesium a metal?
Yes. Magnesium is a alkaline earth metal.
Where is magnesium on the periodic table?
Magnesium is in group 2 (alkaline earth metals), period 3, in the s-block.
Data: Periodic-Table-JSON (CC BY-SA 3.0); standard atomic weights from IUPAC (abridged). Values in brackets are the mass number of the longest-lived isotope.