4BeBeryllium9.0121831 u
Beryllium (Be)
Beryllium is an alkaline earth metal with atomic number 4, in period 2 and group 2 of the periodic table. Its atomic mass is 9.0121831 u and its electron configuration is [He] 2s². Solid at 25 °C.
Key facts
| Atomic number | 4 |
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| Atomic mass | 9.0121831 u |
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| Category | Alkaline Earth Metal |
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| Period | 2 |
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| Group | 2 |
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| Block | s |
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| Electron configuration | [He] 2s² |
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| Electrons per shell | 2, 2 |
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| Electronegativity (Pauling) | 1.57 |
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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 | 1560 K1286.85 °C |
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| Boiling point | 2743 K2469.85 °C |
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| Density | 1.848 g/cm³ |
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Atomic properties
| First ionization energy | 9.323 eV |
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| Electron affinity | 0 kJ/mol |
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| Atomic radius | 112 pm |
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| Covalent radius | 96 pm |
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| Van der Waals radius | 153 pm |
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| Common ions | Be²⁺ |
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| Protons, neutrons, electrons | 4, 5, 4 |
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Physical and thermal properties
| Molar volume | 4.85 cm³/mol |
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| Heat of fusion | 7.95 kJ/mol |
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| Heat of vaporization | 297 kJ/mol |
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| Specific heat | 1820 J/(kg·K) |
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| Thermal conductivity | 190 W/(m·K) |
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| Thermal expansion | 1.13 × 10⁻⁵ K⁻¹ |
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| Mohs hardness | 5.5 |
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| Young’s modulus | 287 GPa |
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| Crystal structure | Hexagonal close-packed |
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| Magnetic type | Diamagnetic |
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Identification and history
| CAS number | 7440-41-7 |
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| Latin name | Beryllium |
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| Discovered by | Louis Nicolas Vauquelin · 1798 |
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| Named by | --- |
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Natural isotopes
| Isotope | Mass (u) | Abundance |
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| 9Be | 9.012183 | 100 % |
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