Fluorine
Distinguish from fluorene and fluorone.Fluorine (from L.
fluere, meaning "to flow"), is the
chemical element in the
periodic table that has the symbol
F and
atomic number 9. Atomic fluorine is
univalent and is the most chemically reactive and
electronegative of all the elements. In its pure form, it is a
poisonous, pale,
yellow-
green gas, with chemical formula F
2. Like other
halogens, molecular fluorine is highly dangerous; it causes severe chemical burns on contact with skin.
Pure fluorine (F
2, since fluorine is
diatomic) is a corrosive pale yellow
gas that is a powerful
oxidizing agent. It is the most reactive and electronegative of all the elements, and readily forms compounds with most other elements. Fluorine even combines with the
noble gases,
krypton,
xenon, and
radon. Even in dark, cool conditions, fluorine reacts explosively with
hydrogen. It is so reactive that
glass,
metals, and even
water, as well as other substances, burn with a bright flame in a jet of fluorine gas. It is far too reactive to be found in elemental form and has such an affinity for most elements, including
silicon, that it can neither be prepared nor be kept in glass vessels. In moist air it reacts with water to form the equally dangerous
hydrofluoric acid .
In aqueous solution, fluorine commonly occurs as the fluoride ion F
-. Other forms are fluoro-
complexes, such as [FeF
4]
-, or H
2F
+.
Fluorides are compounds that combine fluoride with some positively charged counterpart. They often consist of
ions. Fluorine compounds with metals are among the most stable of salts.
Atomic fluorine and molecular fluorine are used for
plasma etching in
semiconductor manufacturing,
flat panel display production and
MEMS fabrication. Other uses:
*
Hydrofluoric acid (chemical formula
HF) is used to etch glass in light bulbs and other products.
* Fluorine is indirectly used in the production of low friction
plastics such as
Teflon, and in
halons such as
Freon.
* Along with some of its compounds, fluorine is used in the production of pure
uranium from
uranium hexafluoride and in the synthesis of numerous commercial fluorochemicals, including vitally important pharmaceuticals, agrochemical compounds, lubricants, and textiles.
*
Fluorochlorohydrocarbons are used extensively in
air conditioning and in
refrigeration.
Chlorofluorocarbons have been banned for these applications because they contribute to the
ozone hole.
*
Sulfur hexafluoride is an extremely inert and nontoxic gas, and a member of a class of compounds that are potent
greenhouse gases.
* Many important agents for general anaesthesia such as
sevoflurane,
desflurane, and
isoflurane are
fluorohydrocarbon derivatives.
*
Sodium hexafluoro
aluminate (
cryolite), is used in the electrolysis of aluminium.
* Compounds of fluorine, including
sodium fluoride, are used in
toothpaste to prevent dental cavities. These compounds are also added to municipal water supplies, a process called
water fluoridation, though a combination of health concerns and
urban legends has sometimes led to
controversy.
* In much higher concentrations,
sodium fluoride has been used as an insecticide, especially against cockroaches.
* Fluorides have been used in the past to help molten metal flow, hence the name.
*
18F, a radioactive isotope that emits
positrons, is often used in
positron emission tomography because of its half-life of 110 minutes.
Some researchers including US space scientists in the early 1960s have studied elemental fluorine gas as a possible
rocket propellant due to its exceptionally high
specific impulse. The experiments failed because fluorine was so hard to handle.
Fluorine in the form of
fluorspar (also called
fluorite) (
calcium fluoride) was described in
1530 by
Georgius Agricola for its use as a
flux [Fluoride History Discovery of fluorine ], which is a substance that is used to promote the fusion of
metals or
minerals. In
1670 Schwanhard found that glass was etched when it was exposed to
fluorspar that was treated with
acid.
Karl Scheele and many later researchers, including
Humphry Davy,
Gay-Lussac,
Antoine Lavoisier, and
Louis Thenard all would experiment with hydrofluoric acid, easily obtained by treating calcium fluoride (
fluorspar) with concentrated sulfuric acid.
It was eventually realized that hydrofluoric acid contained a previously unknown element. This element was not isolated for many years after this due to its extreme reactivity - it is separated from its compounds only with difficulty and then it immediately attacks the remaining materials of the compound. Finally, in
1886, fluorine was isolated by
Henri Moissan after almost 74 years of continuous effort. It was an effort which cost several researchers their health or even their lives, and for Moissan, it earned him the 1906 Nobel Prize in chemistry.
The first large scale production of fluorine was needed for the
atomic bomb Manhattan project in
World War II where the compound
uranium hexafluoride (UF
6) was used to separate the
235U and
238U
isotopes of
uranium. Today both the
gaseous diffusion process and the
gas centrifuge process use gaseous (UF
6) to produce
enriched uranium for
nuclear power applications.
The derivation of elemental fluorine from hydrofluoric acid is exceptionally dangerous, killing or blinding several scientists who attempted early experiments on this halogen. These men came to be referred to as "Fluorine Martyrs."
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Both fluorine and HF must be handled with great care and any contact with
skin and
eyes should be strictly avoided. All equipment must be
passivated before exposure to fluorine.
Contact with exposed skin may result in the HF molecule rapidly migrating through the skin and flesh into the bone where it reacts with calcium permanently damaging the bone, followed by cardiac arrest brought on by sudden chemical changes within the body.
Both elemental fluorine and fluoride ions are highly toxic. When it is a free element, fluorine has a characteristic pungent odor that is detectable in concentrations as low as 20 nL/L. It is recommended that the maximum allowable concentration for a daily 8-hour time-weighted exposure is 1 µL/L (
part per million by volume) (lower than, for example,
hydrogen cyanide).
Fluorine is a powerful oxidizer which can cause organic material, combustibles, or other flammable materials to ignite. However, safe handling procedures enable the
transport of liquid fluorine by the ton.
Elemental fluorine is prepared industrially by
Moissan's original process: electrolysis of anhydrous HF in which KHF
2 has been dissolved to provide enough ions for conduction to take place.
In 1986, preparing for a conference to celebrate the 100th anniversary of the discovery of fluorine,
Karl Christe discovered a purely-chemical preparation by reacting together at 150 °C solutions in anhydrous HF of K
2MnF
6 and of
SbF5. This is not a practical synthesis, but demonstrates that electrolysis is not essential.
Fluorine can often be substituted for
hydrogen when it occurs in organic compounds. Through this mechanism, fluorine can have a very large number of
compounds. Fluorine compounds involving noble gases were first synthesised by
Neil Bartlett in
1962 - xenon hexafluoroplatinate, XePtF
6, being the first. Fluorides of
krypton and
radon have also been prepared. Also argon fluorohydride has been prepared, although it is only stable at cryogenic temperatures.This element is recovered from
fluorite,
cryolite, and
fluorapatite.
*
Ammonium fluoride (NH
4F)
*
Antimony pentafluoride (SbF
5)
*
Boron trifluoride (BF
3)
*
Bromine pentafluoride (BrF
5)
*
Bromine trifluoride (BrF
3)
*
Caesium fluoride (CsF)
*
Calcium fluoride (CaF
2)
*
Chlorine pentafluoride (ClF
5)
*
Fluorosulfuric acid (FSO
3(H)
*
Hydrofluoric acid (HF)
*
Iodine pentafluoride (IF
5)
*
Iodine heptafluoride (IF
7)
*
Lithium fluoride (LiF)
*
Nitrogen trifluoride (NF
3)
*
Nitrosyl fluoride (NOF)
*
Nitryl fluoride (NO
2F)
*
Phosphorus trifluoride (PF
3)
*
Phosphorus pentafluoride (PF
5)
*
Plutonium fluoride (PuF
4)
*
Potassium fluoride (KF)
*
Radon difluoride (RnF
2)
*
Silver(I) fluoride (AgF)
*
Silver(II) fluoride (AgF
2)
*
Sodium fluoride (NaF)
*
Sulfur hexafluoride (SF
6)
*
Rubidium fluoride (RbF)
*
Thionyl fluoride (SOF
2)
*
Tungsten(VI) fluoride (WF
6)
*
Uranium hexafluoride (UF
6)
*
Xenon hexafluoroplatinate (XePtF
6)
*
Xenon tetrafluoride (XeF
4)
*
Fluorocarbon*
Isotopes of fluorine*
Fluorine compounds*
Halide minerals*
Los Alamos National Laboratory – Fluorine*
WebElements.com – Fluorine*
It's Elemental – Fluorine*
Picture of liquid fluorine – chemie-master.de*
Chemsoc.org*
Periodic Table of Elements*
Discovery of fluorine
