9FFluorine18.998403163 u
Fluorine (F)
Fluorine is a halogen with atomic number 9, in period 2 and group 17 of the periodic table. Its atomic mass is 18.998403163 u and its electron configuration is [He] 2s² 2p⁵. Gas at 25 °C.
Key facts
| Atomic number | 9 |
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| Atomic mass | 18.998403163 u |
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| Category | Halogen |
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| Period | 2 |
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| Group | 17 |
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| Block | p |
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| Electron configuration | [He] 2s² 2p⁵ |
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| Electrons per shell | 2, 7 |
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| Electronegativity (Pauling) | 3.98 |
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| Oxidation states | −1common in bold |
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| State at 25 °C | Gas |
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| Melting point | 53.5 K−219.65 °C |
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| Boiling point | 85.03 K−188.12 °C |
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| Density | 1.696 g/L |
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Atomic properties
| First ionization energy | 17.423 eV |
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| Electron affinity | 322.2 kJ/mol |
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| Atomic radius | 73 pm |
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| Covalent radius | 57 pm |
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| Van der Waals radius | 135 pm |
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| Common ions | F⁻ |
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| Protons, neutrons, electrons | 9, 10, 9 |
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Physical and thermal properties
| Molar volume | 11.2 cm³/mol |
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| Heat of fusion | 0.26 kJ/mol |
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| Heat of vaporization | 3.27 kJ/mol |
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| Specific heat | 824 J/(kg·K) |
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| Thermal conductivity | 0.0277 W/(m·K) |
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| Thermal expansion | --- |
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| Mohs hardness | --- |
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| Young’s modulus | --- |
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| Crystal structure | Base-centered monoclinic |
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| Magnetic type | Diamagnetic |
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Identification and history
| CAS number | 7782-41-4 |
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| Latin name | Fluorum |
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| Discovered by | Henri Moissan · 1886 |
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| Named by | Humphry Davy |
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Natural isotopes
| Isotope | Mass (u) | Abundance |
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| 19F | 18.998403 | 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.
See Fluorine in the app
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Periodic Table