The Elements : Fluorine


Name Symbol Atomic Number Electronic Structure Melting Point (°C) Boiling Point (°C)
 Fluorine  F 9 2 - 7 -219.62 -188.12

Element number 9 is called Fluorine. Its symbol is F.

The name comes from a mineral Fluorspar (Calcium Fluoride, CaF2) which is German for "flowing rock". Fluorspar is a mineral that is added to other minerals to lower the melting point. This is useful in some forms of mineral extraction.

The electrons in the Fluorine atom are arranged in two shells: 2, 7. The second electron shell of an atom can only hold eight electrons so Fluorine is one short of this stable arrangement. This fact governs the chemistry of the element.

Fluorine is the most reactive element known.

To extract an element from its compounds you would normally react it with a more reactive element. For example Iron can be extracted from its ore (Iron Oxide, FeO) by adding Carbon and heating. The Carbon reacts with the Oxygen pulling it away from the Iron Oxide to leave Iron. The Carbon becomes Carbon Dioxide.

The problem with Fluorine is that this process does not work. There are no elements more reactive than Fluorine.

Fluorine is extracted from its compounds by using electricity. For example if an electric current is passed through water, the water is split into Hydrogen and Oxygen and each elements bubbles away from one of the electrodes. This process is called electrolysis.

Even using electrolysis isolating Fluorine is complicated and has to be done in the absence of moisture, glass and organic substances like rubber or grease. Only the most resistant materials can be used as container and electrodes.

The element itself is a diatomic molecule (F2). It is a pale yellow, pungent and highly poisonous gas. Several chemists were blinded or killed in attempting to produce or study the element.

Most elements and many compounds react with fluorine, often violently.

Even water burns in a jet of Fluorine. The reaction with water (H2O) is one of the few that liberates Oxygen. The reaction is so violent that some of the Oxygen (O2) is formed as Ozone (O3).

A mixture of Fluorine and Hydrogen reacts explosively even in the dark and at very low temperature to form Hydrogen Fluoride (HF). Hydrogen Fluoride dissolved in water forms Hydrofluoric Acid. This substance attacks glass, which is unusual.

Fluorine even reacts with some of the normally inert Noble Gases (like Krypton and Xenon) which form no other compounds.

Compounds between metals and Fluorine and called Fluorides. Most are salt-like crystalline solids. Fluorine and similar elements are known as Halogens (makers of salts). Sodium Fluoride ONaF) is added to toothpaste to prevent tooth decay.

In Organic Chemistry, the Fluorine atom is of a similar size to Hydrogen so can replace the latter. There is a series of Organic Compounds between Carbon and Fluorine called Fluorocarbons. They are analogous to the Hydrocarbons but more stable and not flammable. The liquids are used as refrigerants because they don't react with their surroundings. They also used to be used in aerosols. Unfortunately, these would escape into the upper atmosphere and react with the Ozone there.

The solid Fluorocarbons are very resistant to chemicals and heat (like Teflon, used in non-stick cooking pans).

Many Fluorine compounds are poisonous.

One of the most important compounds of Fluorine is Uranium Hexafluoride, UF6. This is a gas and is used to separate different isotopes of Uranium for nuclear power (and weapons). This is best done using large centrifuges.

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