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Fluorine is the chemical element with atomic number 9, symbol F

Fluorine is the chemical element with atomic number 9, symbol F

Fluorine is the chemical element with atomic number 9, symbol F

Fluorine is the chemical element with atomic number 9, symbol F

It is the first element of the group of halogens. The corresponding single body is difluor (made up of F2 molecules), often referred to simply as fluorine. The fluoride ion from dissolved fluoride salts inhibits dental cavities, and so finds use in toothpaste and water fluoridation. Global fluorochemical sales amount to more than US$15 billion a year.

It is the most chemically and electronegatively reactive yellow-green toxic univalent halogen gas of all the elements. In its pure form, he is very dangerous, can cause severe chemical burns so in contact with the skin.

The only stable isotope is 19F. The least unstable radioisotope is 18F, whose half-life is just under 2 h and which transmutes into oxygen-18 (in 97% of cases by β + decay and otherwise by electron capture).

Fluorine is the most reactive of the chemical elements, it is also generally linked to other elementsa. It has the strongest electronegativity, with a value of 3.98. It is the 13th most abundant element in the earth’s crust. Some plants and some bacteria can synthesize fluorinated compounds, but fluoride has no metabolic role in mammals.

Under normal temperature and pressure conditions, the single fluorine body appears as difluor F2, a pale yellow, very toxic and extremely corrosive diatomic gas. The melting point of difluor is −219 ° C and its boiling point of −188 ° C, temperatures between which difluor is liquid, with a density of 1,500 kg · m-3. Fluoride causes very serious burns on contact with the skin, mucous membranes, and bones. Georgius Agricola already described the existence of fluorine in 1530 but this element was not isolated until 1886, by Henri Moissan.

Usage of Fluorine

Difluor is too reactive for direct use in its pure state. Its many chemical compounds, on the other hand, have a multitude of applications.

Some examples :

Health impact

Small amounts of fluoride are naturally present in water, air, plants, animals. As a result, humans are exposed to fluoride through the food, the water they drink and the air they breathe. Fluoride can be found in any type of food in relatively small amounts. Higher amounts of fluoride are found in tea and shellfish. Fluoride is essential for maintaining the strength of our bones. It can also protect us against dental cavities, when used as toothpaste twice a day. If fluoride is taken in too frequently, it can cause osteoporosis and cavities, it can damage the kidneys, bones, nerves and muscles.
Fluorine gas is rejected by industries. This gas is very dangerous, at very high concentrations it can cause death. In low concentrations, it causes irritation to the eyes and nose.

Environmental impact

Fluoride occurs naturally in the earth’s crust where it can be found in rocks, coal and clay. Fluoride is dispersed in the air when the soil is blown away. Hydrogen fluoride can be released into the air during combustion processes in industry. Fluoride in the air eventually falls back on the ground or in the water. When fluorine is bonded to very small particles, it can stay in the air for a long time.
When fluorine in the air is found in water, it is deposited in the sediment. When it settles on the ground, fluorine binds strongly to the particles. In the environment, fluorine can change shape.
Fluoride found in soil can accumulate in plants. The amount taken up by plants depends on the type of plant, the type of soil, and the amount and form of fluoride present in the soil. For plants that are sensitive to fluoride exposures, even low concentrations can cause damage and hamper growth.
Animals that consume plants containing fluoride can accumulate significant amounts in their bodies. Fluoride first accumulates in the bones. An animal exposed to high concentrations of fluoride suffers from cavities and bone breakdown. Too much fluoride can also interfere with the development of the nails.

Fluorine in the periodic table

Atomic number (Z) 9
Group group 17 (halogens)
Period period 2
Block   p-block
Electron configuration [He] 2s2 2p5
Electrons per shell 2, 7

Physical properties

Physical properties
Phase at STP gas
Melting point (F2) 53.48 K ​(−219.67 °C, ​−363.41 °F)
Boiling point (F2) 85.03 K ​(−188.11 °C, ​−306.60 °F)
Density (at STP) 1.696 g/L
when liquid (at b.p.) 1.505 g/cm3
Triple point 53.48 K, ​90 kPa
Critical point 144.41 K, 5.1724 MPa
Heat of vaporization 6.51 kJ/mol
Molar heat capacity Cp: 31 J/(mol·K) (at 21.1 °C)
Cv: 23 J/(mol·K) (at 21.1 °C)

Vapor pressure

P (Pa) 1 10 100 1 k 10 k 100 k
at T (K) 38 44 50 58 69 85

Atomic properties

Atomic properties
Oxidation states −1 (oxidizes oxygen)
Electronegativity Pauling scale: 3.98
Ionization energies
  • 1st: 1681 kJ/mol
  • 2nd: 3374 kJ/mol
  • 3rd: 6147 kJ/mol
Covalent radius 64 pm
Van der Waals radius 135 pm

Other properties

Other properties
Natural occurrence primordial
Crystal structure ​cubic
Thermal conductivity 0.02591 W/(m·K)
Magnetic ordering diamagnetic (−1.2×10−4)
CAS Number 7782-41-4


Naming after the mineral fluorite, itself named after Latin fluo (to flow, in smelting)
Discovery André-Marie Ampère (1810)
First isolation Henri Moissan (June 26, 1886)
Named by Humphry Davy

Main isotopes

Main isotopes of fluorine
Iso­tope Abun­dance Half-life (t1/2) Decay mode Pro­duct
18F trace 109.8 min β+ (97%) 18O
ε (3%) 18O
19F 100% stable

Periodic Table of Elements | Complete List of Chemical Elements by Group, Name, Symbol, Color and Type

Periodic Table of Elements | Complete List of Chemical Elements by Group, Name, Symbol, Color and Type

Sources: Royal Society of Chemistry, ChemicoolLive ScienceRoyal Society of Chemistry

Photo credit: Prof. Dr. Sebastian Riedel (Freie Universität Berlin) / Wikimedia Commons

Photo explanation: Liquid fluorine at -196°C (-320,8°F)

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