Quick Facts
| Property | Value |
|---|---|
| Symbol | F |
| Atomic Number | 9 |
| Atomic Mass | 18.998 u |
| Category | Halogen |
| Period | 2 |
| Group | 17 |
| Block | p |
| Electron Configuration | [He] 2s² 2p⁵ |
Physical Properties
| Property | Value |
|---|---|
| State at 20°C | Gas |
| Density | 0.001696 g/cm³ |
| Melting Point | -219.67°C (53.48 K) |
| Boiling Point | -188.11°C (85.04 K) |
| Appearance | Pale yellow gas |
Atomic Properties
| Property | Value |
|---|---|
| Electron Configuration | [He] 2s² 2p⁵ |
| Electronegativity | 3.98 (Pauling scale) |
| First Ionization Energy | 1681.0 kJ/mol |
| Atomic Radius | 50 pm |
| Covalent Radius | 57 pm |
| Van der Waals Radius | 147 pm |
History and Discovery
Discovered by: Henri Moissan Year of Discovery: 1886 Location: Paris, France
Etymology
The name "fluorine" comes from the Latin "fluere" meaning "to flow," referring to the mineral fluorite (calcium fluoride), which was used as a flux in metal smelting to lower melting points.
Discovery Story
Fluorine's existence was suspected for decades before its isolation. Many chemists were injured or killed attempting to isolate it. Henri Moissan finally succeeded in 1886 by electrolyzing potassium bifluoride (KHF₂) dissolved in anhydrous hydrogen fluoride, using platinum-iridium electrodes. He received the Nobel Prize in Chemistry in 1906 for this work.
Isotopes
| Isotope | Natural Abundance | Half-life | Decay Mode |
|---|---|---|---|
| ¹⁹F | 100% | Stable | - |
| ¹⁸F | Synthetic | 109.77 min | β⁺ |
Occurrence
Natural Abundance
Fluorine is the 13th most abundant element in Earth's crust (about 585 ppm). It never occurs free in nature due to its extreme reactivity. It is found in minerals such as fluorite (CaF₂), cryolite (Na₃AlF₆), and fluorapatite (Ca₅(PO₄)₃F).
Extraction and Production
- Electrolysis: Moissan's method is still used—electrolyzing KHF₂ in anhydrous HF
- No Chemical Method: No chemical reaction can release F₂ from its compounds
- Sources: Primarily fluorite and phosphate rock (as a byproduct)
Applications and Uses
Industrial Applications
- Uranium enrichment (uranium hexafluoride UF₆)
- Production of fluoropolymers (Teflon/PTFE)
- Semiconductor etching
- Refrigerants (HFCs) - replacing CFCs
Chemical Applications
- Synthesis of fluorinated compounds
- Fluorination of organic molecules
- Production of sulfur hexafluoride (electrical insulator)
Medical and Dental
- Dental fluoride treatments (prevents cavities)
- Water fluoridation
- Fluorine-18 for PET scans
- Fluorinated pharmaceuticals
Other Uses
- Non-stick coatings (PTFE)
- Stain-resistant fabrics
- Gore-Tex waterproof materials
Biological Role
Fluorine has no essential biological role, though fluoride ions strengthen tooth enamel and bones at low concentrations.
In the Human Body
- Fluoride accumulates in bones and teeth
- May strengthen tooth enamel (hydroxyapatite → fluorapatite)
- Total body content: about 2.6 g in adults
Dietary Sources
Fluoridated water, tea, seafood, and some vegetables contain fluoride.
Safety and Hazards
Toxicity
Fluorine is extremely toxic and corrosive. It reacts violently with almost all substances. Hydrogen fluoride (HF) is particularly dangerous as it penetrates skin and can cause deep tissue damage and systemic toxicity.
Handling Precautions
- Most reactive and electronegative of all elements
- Reacts violently with water, organic matter, and most materials
- Specialized equipment required (passivated metals, fluoropolymer containers)
- Full protective equipment essential
- HF exposure requires immediate specialized medical treatment
Environmental Impact
CFCs (chlorofluorocarbons) caused ozone depletion and are now banned. HFCs are potent greenhouse gases. Fluoride pollution can affect wildlife and ecosystems.
Interesting Facts
- Fluorine is the most electronegative element—it pulls electrons more strongly than any other
- The fluorine-carbon bond is one of the strongest in chemistry, making fluorocarbons extremely stable
- Teflon (PTFE) was accidentally discovered in 1938 and revolutionized non-stick applications
- Several chemists died attempting to isolate fluorine before Moissan succeeded
- Fluorine is so reactive it can even react with some noble gases (xenon, krypton)