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The Element Fluorine

[Click for Isotope Data]





Atomic Number: 9

Atomic Weight: 18.998403163

Melting Point: 53.53 K (-219.62°C or -363.32°F)

Boiling Point: 85.03 K (-188.12°C or -306.62°F)

Density: 0.001696 grams per cubic centimeter

Phase at Room Temperature: Gas

Element Classification: Non-metal

Period Number: 2    Group Number: 17    Group Name: Halogen

What's in a name? From the Latin and French words for flow, fluere.

Say what? Fluorine is pronounced as FLU-eh-reen or as FLU-eh-rin.

History and Uses:

Fluorine is the most reactive of all elements and no chemical substance is capable of freeing fluorine from any of its compounds. For this reason, fluorine does not occur free in nature and was extremely difficult for scientists to isolate. The first recorded use of a fluorine compound dates to around 1670 to a set of instructions for etching glass that called for Bohemian emerald (CaF2). Chemists attempted to identify the material that was capable of etching glass and George Gore was able to produce a small amount of fluorine through an electrolytic process in 1869. Unknown to Gore, fluorine gas explosively combines with hydrogen gas. That is exactly what happened in Gore's experiment when the fluorine gas that formed on one electrode combined with the hydrogen gas that formed on the other electrode. Ferdinand Frederic Henri Moissan, a French chemist, was the first to successfully isolate fluorine in 1886. He did this through the electrolysis of potassium fluoride (KF) and hydrofluoric acid (HF). He also completely isolated the fluorine gas from the hydrogen gas and he built his electrolysis device completely from platinum. His work was so impressive that he was awarded the Nobel Prize for chemistry in 1906. Today, fluorine is still produced through the electrolysis of potassium fluoride and hydrofluoric acid as well as through the electrolysis of molten potassium acid fluoride (KHF2).

Fluorine is added to city water supplies in the proportion of about one part per million to help prevent tooth decay. Sodium fluoride (NaF), stannous(II) fluoride (SnF2) and sodium monofluorophosphate (Na2PO3F) are all fluorine compounds added to toothpaste, also to help prevent tooth decay. Hydrofluoric acid (HF) is used to etch glass, including most of the glass used in light bulbs. Uranium hexafluoride (UF6) is used to separate isotopes of uranium. Crystals of calcium fluoride (CaF2), also known as fluorite and fluorspar, are used to make lenses to focus infrared light. Fluorine joins with carbon to form a class of compounds known as fluorocarbons. Some of these compounds, such as dichlorodifluoromethane (CF2Cl2), were widely used in air conditioning and refrigeration systems and in aerosol spray cans, but have been phased out due to the damage they were causing to the earth's ozone layer.

Estimated Crustal Abundance: 5.85×102 milligrams per kilogram

Estimated Oceanic Abundance: 1.3 milligrams per liter

Number of Stable Isotopes: 1   (View all isotope data)

Ionization Energy: 17.423 eV

Oxidation States: -1

Electron Shell Configuration:


2s2   2p5