Fluorine (F) is a chemical element with an atomic number of 9 in the periodic table of elements. It’s the 13th most abundant element found in Earth’s crust with a concentration of 950 ppm in the upper layers. This univalent poisonous gaseous halogen element of the periodic table forms a vast number of compounds with the other chemical elements, even with the noble gases krypton, xenon, and radon. Fluorides, as the most common fluorine compounds, find especially important use in dental medicine.
Chemical and Physical Properties of Fluorine
The symbol in the periodic table of elements: F
Atomic number: 9
Atomic weight (mass): 18.998403 g.mol-1
Group number: 17 (Halogens)
Color: A yellowish-green substance with an intensive odor
Physical state: Gaseous at room temperature
Half-life: From 500(60)×10−24 s to 109.739 minutes
Electronegativity according to Pauling: 3.98
Density: 1.8*10-3 g.cm-3 at 20°C
Melting point: -219.6°C
Boiling point: -188°C
Van der Waals radius: 0.135 nm
Ionic radius: 0.136 nm (-1); 0.007 (+7)
Most characteristic isotope:19F
Electronic shell: [He] 2s22p5
The energy of the first ionization: 1680.6 kJ.mol-1
The energy of the second ionization: 3134 kJ.mol-1
The energy of the third ionization: 6050 kJ mol-1
Discovery date: In 1886 by Henri Moissan
With the periodic table symbol (F), atomic number 9, atomic mass of 18.998403 g.mol-1, and electron configuration [He] 2s22p5, fluorine is the lightest halogen and most reactive of all elements in the periodic table. This very pale yellow-green corrosive gas with a strong, pungent odor reaches its boiling point at -188°C, while the melting point is achieved at -219.6°C.
Having an electronegativity of 3.98 according to Pauling and one valence electron, fluorine is the most electronegative element of the periodic table. The free fluorine element exists as an F– ion due to the fact that one fluorine atom requires only one electron in order to achieve stability of the electron configuration.
It’s this one atom of fluorine that determines the chemical properties of an entire molecule. In comparison, оxygen and chlorine are similarly electronegative elements.
How Was Fluorine Discovered?
Back through the centuries, in the early 1500s, the German scholar Georgius Agricola (1494 – 1555) came across a mineral in his scientific research that he labeled as fluorspar. According to his findings, when the mineral was added to the molten metallic ores, they became more liquid and easier to handle. Little did he know at that time that the substance in his hands was fluorine containing calcium fluoride (CaF2).
During the 1800s, many great chemists and scientific researchers, such as Scheele, Davy, Lavoisier, and Gay-Lussacmany, have performed a series of experiments with hydrogen fluoride gas with no tangible results. Also, some of the scientists that had to work with hydrofluoric acid sooner or later had faced fatal consequences upon their lives. In some of the cases, exposure of only a few hundred milliliters of the hydrogen fluoride and water solution proved to be extremely dangerous.
The Toll of the Violently Reactive Gas
Namely, when this acid would come into skin contact and penetrate the deeper layers of the bodily tissues, it would begin to form insoluble salts by bonding to atoms of calcium and magnesium, leaving the metabolic enzymes without their key elements. Due to the rapid loss of calcium and magnesium, the bones would then start to degrade, and the muscles (including the heart) would become dysfunctional, leading to the collapse of all bodily systems.
The Belgian chemist Paulin Louyet, and his French colleague Jérôme Nicklès were among those brave scientists who had exposed themselves to the hazardous influence of hydrofluoric acid in an attempt to isolate elemental fluorine (F2).
The Achievements of Henri Moissan
In 1886, the French chemist Henri Moissan (1852 – 1907) embarked on solving what seemed to be an unsolvable riddle in the world of chemistry – how to isolate the pure elemental form of fluorine? Following the scientific claims of both Humphrey Davy and André-Marie Ampere that there is an unknown substance in the fluoride salts that’s triggering volatile reactions, Moissan attempted high-temperature electrolysis on the molten salts in order to trace the substance. Indeed, the resulting corrosion of the platinum vessels he had constructed after the electrolysis proved to him that he’s on the right track to discovering something revolutionary in the world of chemistry.
In his second attempt, this Parisian born scientist electrolyzed condensed hydrogen fluoride at –50°C in a platinum tube. The result was a steady stream of gas, confirmed by the Academy of sciences as the lightest halogen element – fluorine (F).
In 1906, Henri Moissan was awarded the Nobel Prize for Chemistry for the isolation of the element fluorine and the development of the Moissan electric furnace. Unfortunately, he enjoyed the honors for only two short months after the ceremony. Just like his fellow chemists, Louyet and Nicklès, Moissan also had to pay the highest price for working with the most volatile and highly reactive gaseous substance.
How Did Fluorine Get Its Name?
Fluorine got its name after the suggestion of the British chemist Sir Humphry Davy. He found it suitable to name the new element after the mineral containing the elemental form of this halogen in great quantities, fluorite, as well as for its presence in fluoric acid. The origin of the name comes from the Latin word ‘fluere’, which means ‘to flow’.
Where Can You Find Fluorine?
Fluorine is a highly reactive halogen gas. Hence, it’s widely distributed in nature and is produced in a lab. In nature, fluorine is found in rocks, coal, and clay. Dispersed in a wide range of minerals, fluorine is most commonly traced to fluorite, fluorspar (calcium fluoride), and cryolite. Fluorine also occurs in surface waters and groundwater, as well as a trace element in both humans and animals.
For commercial uses, the lightest of halogens can be also obtained by conducting electrolysis of a potassium fluoride/hydrogen fluoride solution (KHF2) in anhydrous hydrofluoric acid. China, Mexico, and Western Europe are where the world’s largest fluorite mines are located.
Fluorine in Everyday Life
This chemical element forms a long list of inorganic compounds with hydrogen, metals, nonmetals, and noble gases. Among them, fluorides have the most versatile use in everyday life:
- In the field of medicine, fluorides are added to toothpaste as cariostatics in order to help prevent dental cavity formation and decay of the tooth enamel;
- In the production of fluorocarbons and aluminum fluorides; fluorine compounds applied in the process of aluminum production enhance the conductivity of the aluminum solution;
- Sulfur hexafluoride is used in high-power electricity transformers;
- Chlorofluorocarbons are used in the manufacturing process of air conditioners and refrigerators;
- In electrical transformers as a nontoxic insulator, air conditioning systems, propellants and solvents make use of fluoride also;
- Uranium hexafluoride compound is applied in the process of uranium isotopes separation required for the production of nuclear reactor fuel or atom bombs;
- As fluorochemicals, fluorides are used in the production of the biocompatible and non-sticking material teflon that is further applied in the manufacturing of surgical implants, kitchen appliances, as well as in cosmetic and reconstructive surgery;
- For manufacturing of anti-inflammatory medications, antibiotics, enzyme inhibitors;
- Fluorodeoxyglucose is used in positron emission tomography and similar imaging studies;
- For making the basis of Gore-Tex® outdoor protective clothing;
- Fluorine is also found in a number of household products, such as vitamins, dietary supplements, cleaning agents, etching of light bulb glass, insecticides, and rodenticides.
Many of the fluorine compounds also have a significant application in the field of electrochemistry and manufacture of electrochemical devices, such as batteries, fuel cells, sensors, in processes of refining metals, electroplating, etc. In particular, special compounds of nonmetal fluorides and fluorinated polymers are applied in the production of rechargeable lithium batteries and polymer electrolyte fuel cells that are further used as power sources of portable devices, electric vehicles, etc.
Fluorides and Health
Fluoride is one of the essential trace elements found in both animals and humans. There’s an average of 3 milligrams of fluoride in the human body. Nearly 99% of it is accumulated in our bones and teeth. Hence, this mineral participates in the formation and mineralization of the bones and teeth. Present in the form of calcium fluoride, fluoride is responsible for the hardening of the tooth enamel, which makes for strong and healthy teeth. For this, it’s been said that fluoride has a cariostatic effect, i.e. prevents teeth decay.
Both deficient consumption (fluorine deficiency) and excess consumption (fluorine poisoning) of products rich in fluorine can lead to severe health problems.
Fluoridated Toothpaste and Mouthwash
Extensive consumption of sweets combined with bad oral hygiene inevitably leads to cavities. When multiplying bacteria in the mouth starts to degrade the sugars, they produce acid that harms the teeth. They trigger the process of demineralization of the protective barrier of the teeth, thus causing decay. By adding this trace mineral in toothpaste and mouthwash, these dental products become largely helpful in reducing the risk of dental plaque formation and the development of caries.
Sodium fluoride and sodium monofluorophosphate are the active agents in toothpaste that prevent the formation of tooth cavities. Fluoride in toothpaste supports remineralization of the weakened tooth enamel of the teeth, thus making it firmer and more resistant to dental caries.
Foods Rich in Fluorine
Almost all fruits and vegetables contain some levels of fluorine in them. However, the list of foods richest in this trace element comprises the following items:
- Dill herb;
- Apple juice;
- White rice;
- Black tea (brewed);
- Baked potatoes;
Lower than optimal levels of fluoride in the body may cause a medical condition known as fluoride deficiency characterized by the following signs and symptoms:
- Badly shaped teeth;
- Brittle or weak bones;
- Easily decaying teeth;
- Dental caries;
- Osteosarcoma (bone cancer);
- Teeth plaques;
- Frequent fractures of the bones;
- Weakened immune system;
- Elevated blood pressure;
- Cardiological problems;
- Dysfunction of the thyroid gland;
- Neurotoxic effects.
Fluoridation of Drinking Water
Despite the fact that the weathering of rocks composed of fluoride compounds leave traces of fluoride in the surface waters, the fluoride in the water we drink comes from the water fluoridation process. By adding fluoride to the drinking water, the natural fluoride concentration in it becomes optimized in order to reduce tooth decay and support skeletal health. In this way, the body absorbs the fluoride that accumulates in our bones and teeth which makes them stronger and healthier.
According to the World Health Organization (WHO), water fluoridation promotes both public health and cavity prevention by providing safe drinking water supplies and a safer environment by the regulation of the fluoride levels in water.
How Dangerous Is Fluorine?
Fluorine has a significant role in both the geochemical and biogeochemical systems. However, both the pure, elemental form of fluorine gas and the fluoride ion are highly toxic, destructive, and reactive. According to the American Council of Science and Health, this halogen gas can be extremely dangerous and lethal even at extremely low levels. In addition, since all soil-grown foods contain some levels of fluorine, contamination of the soil with fluorine could lead to food containing toxic levels of this element.
The excessive accumulation of fluoride may lead to medical conditions, such as:
- Dental fluorosis (An abnormal enamel development and staining of the teeth);
- Skeletal fluorosis (A bone disease caused by long-term ingestion of large amounts of fluoride).
Fluoride toxicity in individuals affected by an excess concentration of this trace element in the body may experience the following symptoms and medical conditions:
- Increased salivation;
- Abdominal pain;
- Difficulty in swallowing;
- Muscle cramps;
- Demineralization of bones;
- Teeth discoloration;
- Muscle weakness;
- Shortness of breath;
- Heart palpitations.
Environmental Effects of Fluorine
Fluorine is naturally dispersed in nature as a part of many minerals and salts. Also, hydrogen fluorides are released in the atmosphere by the industries via the processes of combustion, fluoride emissions as fumes, vapors, smokes from industrial factories, etc. This additionally spreads the toxic gas in the air, which can have adverse effects on human health, especially if it’s inhaled.
When released in the air, chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs) severely deplete the ozone from the atmosphere. By this, they contribute to the ‘greenhouse effect’, i.e. the constant increase of the temperature on Earth (global warming), thus changing the global climate. Due to this, these fluorine compounds have been phased out of use nowadays.
Isotopes of Fluorine
Among the seventeen isotopes of fluorine (from 14F to 31F), only the fluorine-19 is a naturally occurring and stable fluorine isotope. With a half-life of 109.739 minutes, the 14F isotope is the longest living fluorine isotope.
|Z||N||Isotopic mass (Da)
[n 2][n 3]
[n 7][n 4]
|Natural abundance (mole fraction)|
|Excitation energy||Normal proportion||Range of variation|
|18F[n 8]||9||9||18.0009373(5)||109.739(9) min||β+ (96.86%)||18O||1+||Trace|
|18mF||1121.36(15) keV||162(7) ns||IT||18F||5+|
|22F||9||13||22.002999(13)||4.23(4) s||β− (89%)||22Ne||(4+)|
|β−, n (11%)||21Ne|
|23F||9||14||23.00353(4)||2.23(14) s||β− (86%)||23Ne||5/2+|
|β−, n (14%)||22Ne|
|24F||9||15||24.00810(10)||384(16) ms||β− (94.1%)||24Ne||3+|
|β−, n (5.9%)||23Ne|
|25F||9||16||25.01217(10)||80(9) ms||β− (76.9%)||25Ne||(5/2+)|
|β−, n (23.1%)||24Ne|
|26F||9||17||26.02002(12)||8.2(9) ms||β− (86.5%)||26Ne||1+|
|β−, n (13.5%)||25Ne|
|26mF||643.4(1) keV||2.2(1) ms||IT (82%)||26F||(4+)|
|β−, n (12%)||25Ne|
|27F||9||18||27.02732(42)||4.9(2) ms||β−, n (77%)||26Ne||5/2+#|
|29F||9||20||29.04310(56)||2.5(3) ms||β−, n (60%)||28Ne||5/2+#|
|31F||9||22||31.06027(59)#||1# ms [>260 ns]||β−||31Ne||5/2+#|
List of Fluorine Compounds
This gaseous element forms a vast and diverse set of organic compounds. When it becomes a part of a compound, fluorine always adopts an oxidation state of −1. It is the most electronegative element that possesses a great inductive effect, as well as a strong tendency to gain an electron. In some of the more complex molecules, this member of the halogen family of the periodic system has the role of a bridging ligand between two metals.
Most commonly, fluorine forms fluorides, hexafluorides, nitrogen fluorides, and organofluorides:
- Actinium fluoride
- Aluminum fluoride
- Aluminum monofluoride
- Antimony trifluoride
- Argon fluorohydride
- Arsenic trifluoride
- Barium fluoride
- Beryllium fluoride
- Bismuth trifluoride
- Boron monofluoride
- Bromine monofluoride
- Cadmium fluoride
- Caesium fluoride
- Calcium fluoride
- Carbon monofluoride
- Cerium(IV) fluoride
- Chlorine fluoride
- Chromium(IV) fluoride
- Chromyl fluoride
- Cobalt(II) fluoride
- Copper(I) fluoride
- Curium(III) fluoride
- Cyanogen fluoride
- Dioxygen difluoride
- Ditellurium decafluoride
- Dysprosium(III) fluoride
- Erbium(III) fluoride
- Europium(II) fluoride
- Fluorophosphate glass
- Gadolinium(III) fluoride
- Gallium(III) fluoride
- Germanium difluoride
- Germanium tetrafluoride
- Gold heptafluoride
- Gold(I) fluoride
- Hafnium tetrafluoride
- Holmium(III) fluoride
- Hydrofluoric acid
- Hydrogen fluoride
- Indium(III) fluoride
- Iodate fluoride
- Iridium(V) fluoride
- Iron(II) fluoride
- Krypton difluoride
- Lanthanum trifluoride
- Lead tetrafluoride
- Lithium fluoride
- Lutetium(III) fluoride
- Magnesium fluoride
- Manganese(II) fluoride
- Mercury(I) fluoride
- Methylphosphonyl difluoride
- Molybdenum hexafluoride
- Neodymium fluoride
- Neodymium-doped yttrium lithium fluoride
- Neptunium(III) fluoride
- Nickel(II) fluoride
- Niobium(IV) fluoride
- Nitrogen fluoride
- Nitrosyl fluoride
- Nitryl fluoride
- Osmium pentafluoride
- Oxygen difluoride
- Palladium fluoride
- Phosphorus pentafluoride
- Platinum hexafluoride
- Plutonium hexafluoride
- Polonium hexafluoride
- Potassium aluminum fluoride
- Praseodymium(III) fluoride
- Promethium(III) fluoride
- Radium fluoride
- Radon difluoride
- Rhenium heptafluoride
- Rhenium hexafluoride
- Rhodium hexafluoride
- Rubidium fluoride
- Ruthenium hexafluoride
- Samarium(III) fluoride
- Scandium fluoride
- Selenite fluoride
- Selenium hexafluoride
- Silicon tetrafluoride
- Silver diamine fluoride
- Strontium fluoride
- Sulfate fluoride
- Sulfur difluoride
- Tantalum pentafluoride
- Technetium hexafluoride
- Tellurium hexafluoride
- Terbium(III) fluoride
- Thallium trifluoride
- Thiazyl fluoride
- Tin(IV) fluoride
- Titanium tetrafluoride
- Tungsten hexafluoride
- Uranium hexafluoride
- Uranyl fluoride
- Vanadium pentafluoride
- Xenon difluoride
- Ytterbium(III) fluoride
- Zinc fluoride
Fluorometallates (Complex Fluorides)
- Ammonium hexafluoroaluminate
- Fluorometholone acetate
- Caesium hexafluorocobaltate(IV)
- Caesium hexafluoro-cuprate(IV)
- Dioxygenyl hexafluoroplatinate
- Hexafluorotitanic acid
- Lithium hexafluoro-germanate
- Potassium heptafluorotantalate
- Potassium hexafluoro-cuprate(III)
- Sodium hexafluoroaluminate
- Xenon hexafluoroplatinate
- Xenon hexafluoro-rhodate
Fluorides (Fluorine Salts)
Fluorides are compounds of fluorine with a metal, a nonmetal, or an organic radical that occur both naturally and artificially. In reaction with water, the soluble inorganic fluorides form hydrofluoric acid (HF).
Fluorite Crystal (Fluorspar)
The mineral form of calcium fluoride ( CaF2 ) is the fluorite crystal. Also labeled as fluorspar, this member of the halide minerals occurs in a rich palette of colors, including green, purple, blue, black, yellow, white, pink, red, orange, and brown crystals. This soft mineral also radiates fluorescent light under ultraviolet light.
This golden-brown gemstone is a silicate mineral of aluminum and fluorine that crystalizes in orthorhombic lattices. Depending on the impurities and treatment, the color of this gemstone may vary from a bright yellow hue to deep brown color. The largest deposits of granitic pegmatites and rhyolite lava flows from which this crystal can be naturally obtained are found at the Topaz Mountain in western Utah and Chivinar in South America.
5 Interesting Facts and Explanations
- The synthetically produced chemical element tennessine (117Ts) is also considered to be a halogen, thus belonging to the family of elements comprised of fluorine (F), chlorine (Cl), bromine (Br), iodine (I), and astatine (At).
- Neon and helium are the only chemical elements that do not form a compound with fluorine.
- The difference between fluorine and fluoride is that the former term relates to the dangerous chemical element, while the latter one denotes either a fluorine ion or a compound that contains the element fluorine. While fluorine can be lethal even in the smallest quantities, the fluorides have a beneficial health effect in strictly regulated amounts.
- This halogen gas is so volatile and reactive, that even molecules of water ignite in reaction to fluorine.
- Fluorine is used for making various types of medications, such as anesthetics, tranquilizers, antibiotics, antidepressants, etc.