Fluorine [F] 

CAS-ID: 7782-41-4

An: 9 N: 10

Am: 18.9984032 (5) g/mol

Group No: 17

Group Name: Halogen

Block: p-block  Period: 2

State: gas at 298 K

Colour: pale yellow Classification: Non-metallic

Boiling Point: 85.03K (-188.12°C)

Melting Point: 53.53K (-219.62°C)

Critical temperature: 144K (-129°C)

Density: 1.7g/l

Discovery Information

Who: Henri Moissan

When: 1886

Where: France

Name Origin

Latin: fluo (flow).

 "Fluorine" in different languages.

Sources

Found in the minerals fluorite (CaF2), cryolite (Na2AlF6) and fluorapatite (Ca5(PO4)3F).

Abundance

 Universe: 0.4 ppm (by weight)

 Sun: 0.5 ppm (by weight)

 Carbonaceous meteorite: 89 ppm

 Earth's Crust: 950 ppm

 Seawater:

   Atlantic surface: 1 x 10-4 ppm

   Atlantic deep: 9.6 x 10-5 ppm

   Pacific surface: 1 x 10-4 ppm

   Pacific deep: 4 x 10-5 ppm

 Human:

   37000 ppb by weight

   12000 ppb by atoms

Uses

Combines more readily than any other element. Used in toothpaste as sodium fluoride (NaF) and stannous fluoride (SnF2); also in Teflon.

Hydrofluoric acid (HF) is used to etch glass in light bulbs and other products.

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 (SF6) is an extremely inert and nontoxic gas, and a member of a class of compounds that are potent greenhouse gases.

History

Fluorine in the form of fluorspar (also called fluorite (CaF2)) (calcium fluoride) was described in 1530 by Georgius Agricola for its use as a flux, 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 Wilhelm 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; fluorine can only be prepared from its compounds electrolytically, and then it immediately attacks any susceptible materials in the area. Finally, in 1886, elemental fluorine was isolated by Henri Moissan after almost 74 years of continuous effort by other chemists. It was an effort which cost several researchers their health or even their lives. 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." For Moissan, it earned him the 1906 Nobel Prize in chemistry (Moissan himself lived to be 54, and it is not clear whether his fluorine work shortened his life).

The first large-scale production of fluorine was needed for the atomic bomb Manhattan project in World War II where the compound uranium hexafluoride (UF6) was needed as a gaseous carrier of uranium to separate the 235U and 238U isotopes of uranium. Today both the gaseous diffusion process and the gas centrifuge process use gaseous UF6 to produce enriched uranium for nuclear power applications. In the Manhattan Project, it was found that elemental fluorine was present whenever UF6 was, due to the spontaneous decomposition of this compound into UF4 and F2. The corrosion problem due to the F2 was eventually solved by electrolytically coating all UF6 carrying piping with nickel metal, which resists fluorine's attack. Joints and flexible parts were made from Teflon, then a very recently-discovered fluorine-containing plastic which was not attacked by F2.

Notes

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."

Hazards

Pure fluorine is a very reactive and corrosive gas, with a pungent odour. Both fluorine and HF must be handled with great care and any contact with skin and eyes should be strictly avoided. 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.

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.