Fluorine
Element 9 · Halogen
Fluorine wants electrons more than any other element, and it takes them by force: it attacks nearly every substance, including some noble gases, and only a few materials survive contact unscathed. That ferocity makes pure fluorine a laboratory challenge handled only by specialists with dedicated equipment. Controlled, though, fluorine is a quiet hero: fluoride ions harden tooth enamel, Teflon (PTFE) coats nonstick pans, and fluorine compounds cool refrigerators and enrich uranium fuel. It never occurs free in nature — every atom on Earth is locked in minerals like fluorite.
Key facts
| Atomic number | 9 |
|---|---|
| Atomic weight | 19.00 |
| Category | Halogen |
| Group / Period | 17 / 2 |
| Block | p |
| Electron configuration | 1s2 2s2 2p5 |
| Common oxidation states | -1 |
| State at STP | Gas |
| Electronegativity | 3.98 |
| Atomic radius | 42 pm |
| Density | 0.00170 g/cm³ |
| Melting point | -219.67 °C |
| Boiling point | -188.11 °C |
Occurrence
Fluorine hides in the minerals fluorite and cryolite and in phosphate rocks. Seawater and most groundwater carry small amounts of dissolved fluoride. It never occurs free in nature.
Applications
Fluoride toothpaste and dental treatments
Nonstick PTFE (Teflon) coatings
Refrigerants and propellants
Uranium enrichment (UF6)
Hydrofluoric acid for glass etching
Common compounds
- Hydrogen fluoride (HF)
- Sodium fluoride (NaF)
- Calcium fluoride (CaF2)
- Polytetrafluoroethylene (PTFE)
Fluorine is so aggressive it can set fire to materials — like asbestos and brick — that resist every other chemical.
Data source: IUPAC standard atomic weights 2021