Quick answerFluorine (F) is a halogen with atomic number 9 and an atomic mass of 18.998 (2023), in group 17, period 2. It was discovered by Henri Moissan in 1886. It is used for fluoride toothpaste and water treatment and Teflon non-stick coatings. Its electron configuration is [He] 2s2 2p5.
Fluorine is the most reactive element there is, so eager to bond that it can set even glass and some metals on fire. Tamed, it protects teeth as fluoride in toothpaste and drinking water, and it forms Teflon, the non-stick coating on pans. It also enriches uranium for nuclear power and etches the silicon chips inside every computer.
Key facts
| Symbol | F |
|---|---|
| Atomic number | 9 |
| Atomic mass | 18.998 (IUPAC standard atomic weight, 2023) |
| Category | halogen |
| Group | 17 |
| Period | 2 |
| Block | p-block |
| Electron configuration | [He] 2s2 2p5 |
| Discovered | Henri Moissan, 1886 |
| Uses | fluoride toothpaste and water treatment, Teflon non-stick coatings, uranium enrichment, etching silicon chips, refrigerants |
Overview
Fluorine is the most reactive element in the periodic table, so eager to bond that it can set glass, water and some metals on fire. It has atomic number 9, an atomic mass of 18.998, and the electron configuration [He] 2s2 2p5, with one electron short of a full shell, which it grabs from almost anything it meets. It sits in group 17, the halogens, in period 2. Henri Moissan isolated it in 1886 after decades of failed attempts that had injured or killed earlier chemists, and he won the Nobel Prize for the feat. Because pure fluorine is so dangerous, it is almost always used in compounds. The best known is fluoride, added to toothpaste and drinking water to protect teeth from decay, one of public health's great successes. Fluorine also forms Teflon, the slippery non-stick coating on pans, and it is used to enrich uranium for nuclear power, to etch silicon chips, and to make refrigerants and medicines. It occurs naturally in minerals such as fluorite and in seawater, never as a free gas, because it reacts too quickly to survive on its own.
Frequently asked questions
What is fluorine used for?
Fluorine is mainly used as fluoride in toothpaste and drinking water to protect teeth from decay. It also forms Teflon, the non-stick coating on pans, and it is used to enrich uranium for nuclear power, to etch silicon chips, and to make refrigerants and medicines. Pure fluorine is far too reactive to use directly.
What is the symbol for fluorine?
The chemical symbol for fluorine is F, from its Latin name fluere, meaning to flow, because its minerals were used as a flux to help metals melt. It has atomic number 9 and a standard atomic mass of 18.998, and it sits in group 17 and period 2. Henri Moissan isolated it in 1886 after decades of failed attempts.
What is the atomic number of fluorine?
Fluorine has atomic number 9, so it is the ninth element in the periodic table. Its atom holds nine protons and nine electrons, and its standard atomic mass is 18.998. It is a halogen in group 17 and period 2, with the electron configuration [He] 2s2 2p5, one electron short of a full shell, which makes it extremely reactive.
Is fluorine a metal?
No, fluorine is a nonmetal. It is a halogen in group 17 of the periodic table, and at room temperature it is a pale yellow gas. It is the most reactive element, and it forms compounds by grabbing electrons from other elements, which is the opposite of how metals behave. It never occurs as a free gas in nature.
Is fluoride the same as fluorine?
No, fluoride is not the same as fluorine, though it comes from it. Fluorine is a highly reactive pale yellow gas, while fluoride is the stable ion it forms after gaining an electron. Fluoride is what is added to toothpaste and drinking water to protect teeth, and it is safe at those low levels, unlike pure fluorine gas.
Quick quiz
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Keep exploring
- Periodic table — all 118 elements
- Chlorine (Cl) — another halogen, atomic number 17
- Bromine (Br) — another halogen, atomic number 35
- Iodine (I) — another halogen, atomic number 53
- Astatine (At) — another halogen, atomic number 85
- Tennessine (Ts) — another halogen, atomic number 117
Sources & last updated
- CIAAW — Standard Atomic Weights
- PubChem Periodic Table
- Wikipedia — Timeline of chemical element discoveries
Last updated: . Figures are shown with their year; where sources disagree, the value is left out rather than estimated.