31GaGallium69.723 u
Gallium (Ga)
Gallium is a post-transition metal with atomic number 31, in period 4 and group 13 of the periodic table. Its atomic mass is 69.723 u and its electron configuration is [Ar] 3d¹⁰ 4s² 4p¹. Solid at 25 °C.
Key facts
| Atomic number | 31 |
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| Atomic mass | 69.723 u |
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| Category | Post-Transition Metal |
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| Period | 4 |
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| Group | 13 |
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| Block | p |
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| Electron configuration | [Ar] 3d¹⁰ 4s² 4p¹ |
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| Electrons per shell | 2, 8, 18, 3 |
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| Electronegativity (Pauling) | 1.81 |
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| Oxidation states | −5, −4, −2, −1, +1, +2, +3common in bold |
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| State at 25 °C | Solid |
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| Melting point | 302.91 K29.76 °C |
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| Boiling point | 2477 K2203.85 °C |
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| Density | 5.904 g/cm³ |
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Atomic properties
| First ionization energy | 5.999 eV |
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| Electron affinity | 28.9 kJ/mol |
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| Atomic radius | 141 pm |
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| Covalent radius | 122 pm |
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| Van der Waals radius | 187 pm |
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| Common ions | Ga³⁺ |
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| Protons, neutrons, electrons | 31, 39, 31 |
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Physical and thermal properties
| Molar volume | 11.8 cm³/mol |
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| Heat of fusion | 5.59 kJ/mol |
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| Heat of vaporization | 256 kJ/mol |
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| Specific heat | 371 J/(kg·K) |
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| Thermal conductivity | 29 W/(m·K) |
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| Thermal expansion | 0.00012 K⁻¹ |
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| Mohs hardness | 1.5 |
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| Young’s modulus | 9.8 GPa |
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| Crystal structure | Base orthorhombic |
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| Magnetic type | Diamagnetic |
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Identification and history
| CAS number | 7440-55-3 |
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| Latin name | Gallium |
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| Discovered by | Lecoq de Boisbaudran · 1875 |
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| Named by | --- |
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Natural isotopes
| Isotope | Mass (u) | Abundance |
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| 69Ga | 68.925574 | 60.108 % |
| 71Ga | 70.924703 | 39.892 % |
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