Element: Magnesium
General data
| Element name | Magnesium |
|---|---|
| Chemical symbol | Mg |
| Atomic number Z | 12 |
| Year discovered | 1808 |
| Standard state (25°C) | Solid |
| Category | Alkaline earth metal |
| Block | s |
| Atomic mass | 24.305 |
| CPK color | #8AFF00 |
Physical properties
| Melting point | 923 K (650 °C) |
|---|---|
| Boiling point | 1363 K (1090 °C) |
| Density | 1.74 g/cm³ |
Energy properties
| First ionization energy | 7.646 eV |
|---|---|
| Electron affinity | no data |
Atomic structure
| Protons | 12 (Atomic number) |
|---|---|
| Neutrons (Mg-24, most abundant isotope) | 12 |
| Electrons | 12 |
| Electron configuration | [Ne] 3s² |
| Oxidation states | +2 |
| Electronegativity (Pauling) | 1.31 |
| Atomic radius (van der Waals) | 173 pm |
Ionization energies - NIST ASD (12 states)
| State | Charge | Ioniz. energy (eV) | Type |
|---|---|---|---|
| Mg I | 0+ | 7.646236 ± 0.000004 | measured |
| Mg II | 1+ | 15.035271 ± 0.000006 | measured |
| Mg III | 2+ | 80.1436 ± 0.0006 | measured |
| Mg IV | 3+ | 109.2654 ± 0.0012 | semi-empirical |
| Mg V | 4+ | 141.33 ± 0.03 | semi-empirical |
| Mg VI | 5+ | 186.76 ± 0.06 | semi-empirical |
| Mg VII | 6+ | 225.02 ± 0.06 | semi-empirical |
| Mg VIII | 7+ | 265.924 ± 0.019 | semi-empirical |
| Mg IX | 8+ | 327.99 ± 0.04 | semi-empirical |
| Mg X | 9+ | 367.489 ± 0.007 | calculated |
| Mg XI | 10+ | 1761.8049 ± 0.001 | calculated |
| Mg XII | 11+ | 1962.663889 ± 0.000007 | calculated |
Value type as given by NIST ASD: measured - from evaluated experimental data; calculated - from ab initio calculations (mostly highly ionised atoms that have not been measured; for the simplest ones, e.g. H I, the calculation is more accurate than measurement); semi-empirical - from interpolation, extrapolation or another semi-empirical method.
Photos
Isotopes (22)
| A | N | Half-life | Decay |
|---|---|---|---|
| Mg-18 | 6 | unbound (resonance) | 2p |
| Mg-19 | 7 | 4000 fs | 2p |
| Mg-20 | 8 | 90.4 ms | EC/β⁺ |
| Mg-21 | 9 | 120.0 ms | EC/β⁺ |
| Mg-22 | 10 | 3.8745 s | EC/β⁺ |
| Mg-23 | 11 | 11.304 s | EC/β⁺ |
| Mg-24 | 12 | stable | - |
| Mg-25 | 13 | stable | - |
| Mg-26 | 14 | stable | - |
| Mg-27 | 15 | 9.44 min | β⁻ |
| Mg-28 | 16 | 20.915 h | β⁻ |
| Mg-29 | 17 | 1.31 s | β⁻ |
| Mg-30 | 18 | 314 ms | β⁻ |
| Mg-31 | 19 | 270 ms | β⁻ |
| Mg-32 | 20 | 80.4 ms | β⁻ |
| Mg-33 | 21 | 90.2 ms | β⁻ |
| Mg-34 | 22 | 44.9 ms | β⁻ |
| Mg-35 | 23 | 11.3 ms | β⁻ |
| Mg-36 | 24 | 7.2 ms | β⁻ |
| Mg-37 | 25 | 6.4 ms | β⁻ |
| Mg-38 | 26 | 3.1 ms | β⁻ |
| Mg-40 | 28 | unknown | β⁻ |
Data sources
- PubChem Periodic Table API - Retrieved on 29 June 2026 - licence: CC0
- IUPAC CIAAW - Abridged Standard Atomic Weights 2024 - Table version: 2024 - licence: Public domain
- NNDC Wallet Cards 2023 - Data as of 15 October 2024 - licence: Public domain
- NIST Atomic Spectra Database (ASD) - Retrieved on 29 June 2026 - licence: © U.S. Secretary of Commerce
- Images of Elements - Retrieved on 29 June 2026 - licence: CC BY 3.0