Fluorine
Appearance
A very pale yellow-green, dangerously reactive gas. It is the most reactive of all the elements and quickly attacks all metals. Steel wool bursts into flames when exposed to fluorine.
Uses
There was no commercial production of fluorine until the Second World War, when the development of the atom bomb, and other nuclear energy projects, made it necessary to produce large quantities. Before this, fluorine salts, known as fluorides, were for a long time used in welding and for frosting glass.
The element is used to make uranium hexafluoride, needed by the nuclear power industry to separate uranium isotopes. It is also used to make sulfur hexafluoride, the insulating gas for high-power electricity transformers.
In fact, fluorine is used in many fluorochemicals, including solvents and high-temperature plastics, such as Teflon (poly(tetrafluoroethene), PTFE). Teflon is well known for its non-stick properties and is used in frying pans. It is also used for cable insulation, for plumber’s tape and as the basis of Gore-Tex® (used in waterproof shoes and clothing).
Hydrofluoric acid is used for etching the glass of light bulbs and in similar applications.
CFCs (chloro-fluoro-carbons) were once used as aerosol propellants, refrigerants and for ‘blowing’ expanded polystyrene. However, their inertness meant that, once in the atmosphere, they diffused into the stratosphere and destroyed the Earth’s ozone layer. They are now banned.
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Element Facts & Figures
| Atomic Symbol | F |
| Atomic Number | 9 |
| Atomic Weight | 18.998 |
| Melting Point | −210.0°C, −346.0°F, 63.2 K |
| Boiling Point | −188.11°C, −306.6°F, 85.04 K |
| Phase at Room Temperature | Gas |
| Element Classification | Other Non-Metal |
| Period Number | 2 |
| Group | 17 |
Biological role
Fluoride is an essential ion for animals, strengthening teeth and bones. It is added to drinking water in some areas. The presence of fluorides below 2 parts per million in drinking water is believed to prevent dental cavities. However, above this concentration it may cause children’s tooth enamel to become mottled. Fluoride is also added to toothpaste.
The average human body contains about 3 milligrams of fluoride. Too much fluoride is toxic. Elemental fluorine is highly toxic.
Natural abundance
The most common fluorine minerals are fluorite, fluorspar and cryolite, but it is also rather widely distributed in other minerals. It is the 13th most common element in the Earth’s crust.
Fluorine is made by the electrolysis of a solution of potassium hydrogendifluoride (KHF2) in anhydrous hydrofluoric acid.