Fluorine Facts

Fluorine is the ninth element of the periodic table. These fluorine facts contain chemical and physical data along with general information and history.

Element cell for Fluorine
Fluorine periodic table cell.

Basic Fluorine Facts

Name: Fluorine

Atomic Number: 9

Element Symbol: F

Group: 17

Period: 2

Block: p

Element Family: halogen

Atomic Mass: 18.998 403 163(6)

Electron Configuration: [He]2s22p(shorthand) or 1s22s22p(full)

Discovery: Henri Moissan in 1886
Fluorine was known to exist for many years. As early as the mid 1500s, fluorite minerals were added in metallurgy to reduce the melting points of metals. Hydrofluoric acid was used by 18th Century glassmakers to etch glass. No one was able to isolate this elusive element. In 1886, French chemist Henri Moissan finally perfected a technique to isolate pure fluorine gas. Moissan would earn the 1906 Nobel Prize in Chemistry for this feat.

Name Origin: Fluorine is named from an acid made from fluorite mineral known as fluoric acid. Sir Humphry Davy proposed the name of the unknown element in the acid fluorine. fluoro- from the acid and -ine because it had properties of a halogen.


Natural fluorine has one stable isotope:  19F.  18 known radioactive isotopes have been produced under laboratory conditions ranging from 14F to 31F.

Fluorine-19 is a stable isotope containing 10 neutrons and a natural abundance of 100%.

Liquid Fluorine
Liquid fluorine sample at low temperature. Credit: Prof. B. G. Mueller/Creative Commons

Physical Data

Density: 0.001553 g/cm3

Melting Point: 53.48 K ​(−219.67 °C, ​−363.41 °F)

Boiling Point: 85.03 K ​(−188.11 °C, ​−306.60 °F)

Triple Point: 53.48 K at ​90 kPa

Critical Point: 144.41 K at 5.1724 MPa

State at 20ºC: Gas

Heat of Vaporization: 6.51 kJ/mol

Molar Heat Capacity: 23 J/mol·K for constant volume (cv) and 31 J/mol·K for constant pressure (cp )

Fluroine Atom
Electron configuration of a fluorine atom.

Atomic Data

Atomic Radius: 1.47 Å

Covalent Radius: 0.64 Å

Van der Waals Radius:  1.35 Å

Electron Affinity: 1681.045 kJ/mol

Electronegativity: (Pauling scale): 3.98

1st Ionization Energy: 1313.942 kJ/mol

2nd Ionization Energy: 3374.17 kJ/mol

3rd Ionization Energy: 6050.441 kJ/mol

4th Ionization Energy: 8407.713 kJ/mol

5th Ionization Energy: 11022.755 kJ/mol

6th Ionization Energy: 15164.128 kJ/mol

7th Ionization Energy: 17867.734 kJ/mol

8th Ionization Energy: 92038.447 kJ/mol

Oxidation States: -1

Fun Fluorine Facts

  • Fluorine was once known as a chemist killer. Fluorine is a highly reactive element and efforts to isolate it proved dangerous to chemists who attempted to isolate it. Chemists injured or killed by the search for pure fluorine were known as “Fluorine Martyrs”.
  • Some early textbooks and journals have the element symbol Fl for fluorine.
  • Fluorine has the highest electronegativity value of the elements and the second highest electron affinity.
  • Fluoride is the name of the fluorine ion.
  • Fluorine is a pale yellow diatomic gas at room temperatures.
  • Fluorine is highly toxic and corrosive.
  • Fluorine is the 13th most abundant element on Earth, but the 24th most abundant in the universe.
  • The mineral fluorite, or fluorspar, glows in the dark when exposed to light. This is where the term fluorescence comes from. It turns out, fluorine has nothing to do with this property. Small amounts of europium in fluorite causes this effect.
  • Sodium fluoride is the additive in toothpaste and drinking water for preventing cavities in teeth.
  • Fluorine attacks metals. Steel wool will ignite when exposed to pure fluorine gas.
  • Commercial production of fluorine did not exist until it was needed to enrich uranium during World War II. Uranium hexafluoride is used to separate the different uranium isotopes.

Learn more about elements on the periodic table.