Fluorine (F)
Reactive nonmetal
Fluorine is the most reactive and most electronegative element of all. This pale-yellow gas attacks almost every material, yet safely bound in compounds it protects teeth and makes non-stick coatings possible.
Position on the periodic table
Atomic properties
| Atomic number | 9 |
|---|---|
| Atomic mass | 18.9984 amu |
| Electron configuration | 1s2 2s2 2p5 |
| Noble gas shorthand | [He] 2s2 2p5 |
| Electrons per shell | 2, 7 |
| Valence electrons (outer shell) | 7 |
| Common oxidation states | -1 |
| Electronegativity (Pauling) | 3.98 |
| Covalent radius (approx.) | 57 pm |
| First ionization energy | 1681 kJ/mol |
| Electron affinity | 328.2 kJ/mol |
Physical properties
| State at 25 °C | Gas |
|---|---|
| Density | 1.696 g/L |
| Melting point | -219.67 °C (53.48 K) |
| Boiling point | -188.12 °C (85.03 K) |
| Appearance | Not available |
| Radioactive | No |
| Origin | Occurs naturally |
Electron configuration of fluorine
Fluorine's ground-state electron configuration is 1s2 2s2 2p5, usually shortened to [He] 2s2 2p5. Its electrons occupy 2 shells (2, 7), placing it in period 2 of the p-block. The 7 outer-shell electrons drive its bonding behaviour. Explore it interactively in the electron configuration calculator.
Uses of fluorine
- Fluoride in toothpaste and drinking water
- Non-stick PTFE (Teflon) coatings
- Refrigerants
- Etching glass and silicon chips (as HF)
Biological role: Trace amounts strengthen tooth enamel as fluoride; not essential for life.
Occurrence: Never free in nature; found in fluorite (CaF₂) and other minerals.
Common compounds of fluorine
CaF2
Fluorite (calcium fluoride)
HF
Hydrofluoric acid
NaF
Sodium fluoride
History and discovery
Discovered: 1886 — André-Marie Ampère. Name origin: From Latin fluere (to flow) — fluorite ore was used to make metal ores melt more easily.
Henri Moissan finally isolated fluorine in 1886 after decades of failed — and sometimes fatal — attempts by other chemists.
Safety notes
Fluorine gas and hydrofluoric acid are extremely dangerous and never used outside specialist labs.
Educational context only — always follow your school's laboratory rules and never handle chemicals without proper supervision. See our disclaimer.
Practice questions
Quick practice: Fluorine
1. What is the chemical symbol of Fluorine?
2. What is the atomic number of Fluorine?
3. Which category does Fluorine belong to?
4. What is the state of Fluorine at room temperature?
5. Which period of the periodic table is Fluorine in?
Fluorine FAQs
What is the atomic number of fluorine?
Fluorine's atomic number is 9 — every fluorine atom has 9 protons in its nucleus.
What is the symbol for fluorine?
F. From Latin fluere (to flow) — fluorite ore was used to make metal ores melt more easily.
Is fluorine a metal, nonmetal, or metalloid?
Fluorine is classified as a reactive nonmetal.
What state is fluorine at room temperature?
At about 25 °C, fluorine is a gas. It melts at -219.67 °C.
How many valence electrons does fluorine have?
Fluorine has 7 electrons in its outer shell (shell pattern: 2, 7).
What is fluorine used for?
Key uses include: fluoride in toothpaste and drinking water; non-stick ptfe (teflon) coatings; refrigerants.
Related elements
Keep working with this element
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