12MgMagnesium24.305 u
Magnesium (Mg)
Magnesium is an alkaline earth metal with atomic number 12, in period 3 and group 2 of the periodic table. Its atomic mass is 24.305 u and its electron configuration is [Ne] 3s². Solid at 25 °C.
Key facts
| Atomic number | 12 |
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| Atomic mass | 24.305 u |
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| Category | Alkaline Earth Metal |
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| Period | 3 |
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| Group | 2 |
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| Block | s |
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| Electron configuration | [Ne] 3s² |
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| Electrons per shell | 2, 8, 2 |
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| Electronegativity (Pauling) | 1.31 |
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| Oxidation states | +1, +2common in bold |
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| State at 25 °C | Solid |
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| Melting point | 923 K649.85 °C |
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| Boiling point | 1363 K1089.85 °C |
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| Density | 1.738 g/cm³ |
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Atomic properties
| First ionization energy | 7.646 eV |
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| Electron affinity | 0 kJ/mol |
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| Atomic radius | 160 pm |
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| Covalent radius | 141 pm |
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| Van der Waals radius | 173 pm |
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| Common ions | Mg²⁺ |
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| Protons, neutrons, electrons | 12, 12, 12 |
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Physical and thermal properties
| Molar volume | 14 cm³/mol |
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| Heat of fusion | 8.7 kJ/mol |
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| Heat of vaporization | 128 kJ/mol |
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| Specific heat | 1020 J/(kg·K) |
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| Thermal conductivity | 160 W/(m·K) |
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| Thermal expansion | 2.48 × 10⁻⁵ K⁻¹ |
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| Mohs hardness | 2.5 |
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| Young’s modulus | 45 GPa |
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| Crystal structure | Simple hexagonal |
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| Magnetic type | Paramagnetic |
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Identification and history
| CAS number | 7439-95-4 |
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| Latin name | Magnesium |
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| Discovered by | Joseph Black · 1755 |
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| Named by | --- |
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Natural isotopes
| Isotope | Mass (u) | Abundance |
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| 24Mg | 23.985042 | 78.965 % |
| 25Mg | 24.985837 | 10.011 % |
| 26Mg | 25.982593 | 11.025 % |
Data checked against PubChem (NIH), IUPAC, the NIST Atomic Spectra Database and the IAEA (NUBASE and AME), the same data you see in the app.
A dash (---) means there is no reliable published measurement. The app never makes one up.
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Periodic Table