Magnesium
Silvery metallic element belonging to group 2 of the periodic table (alkaline-earth metals). It is essential for living organisms, and is used in a number of light alloys. Chemically very reactive, it forms a protective oxide coating when exposed to air and burns with an intense white flame. It also reacts with sulphur, nitrogen and the halogens. First isolated by Bussy in 1828.
Gallery
Warut Roonguthai, CC BY-SA 3.0 <https://creativecommons.org/licenses/by-sa/3.0>, via Wikimedia Commons
Emission spectrum
Physical Propertiesmass · density · phase · crystal
Atomic Mass
24.3050Da
Density
1.7400g/cm³
Phase (STP)
Solid
Melting Point
923.1K
Boiling Point
1363.2K
Molar Heat
1.0230J/(mol·K)
Crystal Structure
HEX
Lattice Constant
3.210Å
Atomic Radiiatomic · covalent · van der Waals
Atomic (Empirical)
150.00pm
Covalent
139.00pm
Van der Waals
173.00pm
Electronic Propertieselectronegativity · ionization · affinity
Electron Configuration
[Ne] 3s2
Electron Shells
2, 8, 2
Electronegativity
1.31Pauling
Electron Affinity
—
1st Ionization Energy
7.6kJ/mol
Oxidation States
+1, +2
Orbital DiagramAufbau · Hund's rule · Pauli exclusion
Full: 1s2 2s2 2p6 3s2Short: [Ne] 3s2
Ionization Energies (12 known)
Emission Spectrumvisible range · characteristic spectral lines
Abundanceby mass
Log scale · ppm = parts per million by mass
Biological Role
Cofactor for 300+ enzymes. Required for ATP function, DNA synthesis, and muscle relaxation.
Discovery
Discovered By
Sir Humphrey Davy
Named By
—
Year
1808
Nuclear Data
Known Isotopes
23
Stable Isotopes
5
Stable Mass Numbers
24, 25, 26, 39, 41
Natural isotopic abundance (IUPAC recommended values)
Isotopes of Mg23 known
| Nuclide | Z | N | Mass (AMU) | Half-life | Decay | Jπ | Abundance |
|---|---|---|---|---|---|---|---|
| 19Mg | 12 | 7 | 19.034180 | 5.00 ps | 2p (1%) | 1/2- | — |
| 20Mg | 12 | 8 | 20.018763 | 90.4 ms | β⁺ (1%), β⁺p (0.303%) | 0+ | — |
| 21Mg | 12 | 9 | 21.011706 | 120 ms | β⁺ (1%), β⁺p (0.201%), β⁺α (0.00116%), B+pA (0.00016%) | 5/2+ | — |
| 24Mgstable | 12 | 12 | 23.985042 | Stable | stable (1%) | 0+ | 7896.5000% |
| 25Mgstable | 12 | 13 | 24.985837 | Stable | stable (1%) | 5/2+ | 1001.1000% |
| 26Mgstable | 12 | 14 | 25.982593 | Stable | stable (1%) | 0+ | 1102.5000% |
| 39Mgstable | 12 | 27 | 39.045921 | Stable | n, β⁻ | 7/2- | — |
| 40Mg | 12 | 28 | 40.053194 | Unknown | β⁻, β⁻n, 2n | 0+ | — |
| 41Mgstable | 12 | 29 | 41.062373 | Stable | β⁻, β⁻n | 3/2- | — |