This tiny titan is the lightest of the halogens and the most chemically aggressive element known. It doesn’t play nicely with others — except helium, neon, and argon — and it’s the absolute king when it comes to electronegativity.
Fluorine exists as a diatomic molecule (F₂) and forms bonds that are short, strong, and dangerously reactive. One whiff of this pale yellow gas, and you’ll know: this element means business. It’s highly toxic, corrosive, and explosive if mishandled — a real daredevil of the periodic table.
Properties:
Symbol: F
Atomic number: 9
Appearance: Pale yellow gas
Discovery: 1810 by André-Marie Ampère
Group: Reactive Nonmetal
Phase at STP: Gas
Electronegativity: 3.98 (the highest!)
Density: 0.001696 g/cm³
Electron Configuration: 1s² 2s² 2p⁵
Atomic Mass: 18.9984 u
Melting Point: −219.67 °C
Boiling Point: −188.11 °C
🧪 Science-y Stuff
- Electron Shells: K2 L7
- Covalent Radius: 71 pm
- Van der Waals Radius: 147 pm
- Ionization Energies: From 17.42 eV up to a wild 1103.12 eV
- Common Ion: F⁻
- Crystal Structure: Cubic
- Specific Heat Capacity: 0.824 J/g·K
- CAS Registry Number: 7782-41-4
☢️ Isotopic Mayhem
While F-19 is stable and found in nature, Fluorine has a whole party of unstable isotopes:
| Isotope | Mass (u) | Half-life | Decay Mode |
|---|---|---|---|
| F-17 | 17.002 | 64.370 s | β⁺ |
| F-18 | 18.001 | 109.739 min | β⁺ |
| F-20 | 19.999 | 11.163 s | β⁻ |
| F-21 | 20.999 | 4.158 s | β⁻ |
| F-31 | 31.060 | Unknown | β⁻ |
(That’s just the tip of the isotopic iceberg, view all isotopes in the Atomic application.)
Dive Deeper:
Get Atomic – Periodic Table for all data!
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