Fluorine (symbol F) is a chemical element that is very poisonous.  Its atomic number (which is the number of protons in it) is 9, and its atomic mass is 19. It is part of the Group 7 (halogens) on the periodic table of elements.

Properties
Fluorine is a light yellow diatomic gas. It is very reactive gas, which exists as diatomic molecules. It is actually the most reactive element. Fluorine has a very high attraction for electrons, because it is missing one. This makes it the most powerful oxidizing agent. It can rip electrons from water (making oxygen) and ignite propane on contact. It does not need a spark. Metals can catch on fire when placed in a stream of fluorine. After it is reduced by reacting with other things, it forms the stable fluoride ion. Fluorine is very poisonous. Fluorine bonds very strongly with carbon. It can react with the unreactive noble gases. It explodes when mixed with hydrogen. The melting point of fluorine is -363.33°F (-219.62°C), the boiling point is -306.62°F (-188.12°C).

Chemical compounds
Chemical compounds containing fluorine ions are called fluorides. Fluorine only exists in one oxidation state: -1.
Aluminium fluoride
Antimony trifluoride
Antimony pentafluoride
Arsenic trifluoride
Arsenic pentafluoride
Bismuth(III) fluoride
Bismuth(V) fluoride
Bromine trifluoride
Bromine pentafluoride
Chlorine monofluoride
Chlorine trifluoride
Cobalt(II) fluoride
Cobalt(III) fluoride
Disulfur decafluoride
Hydrofluoric acid, a solution of hydrogen fluoride in water
Hydrogen fluoride
Iodine trifluoride
Iodine pentafluoride
Iodine heptafluoride
Manganese(II) fluoride
Manganese(III) fluoride
Manganese(IV) fluoride
Potassium fluoride
Selenium tetrafluoride
Selenium hexafluoride
Silver(I) fluoride, brown-yellow
Silver(II) fluoride, highly reactive, white or gray
Sodium aluminium fluoride, cryolite 
Sodium fluoride
Sulfur hexafluoride
Sulfur tetrafluoride
Tellurium(IV) fluoride
Tellurium(VI) fluoride
Thallium(I) fluoride
Thallium(III) fluoride
Tin(II) fluoride
Tin(IV) fluoride
Zinc fluoride

Occurrence

Fluorine is not found as an element on the earth; it is much too reactive. Several fluorides are found in the earth, though. When calcium phosphate is reacted with sulfuric acid to make phosphoric acid, some hydrofluoric acid is produced. Also, fluorite can be reacted with sulfuric acid to make hydrofluoric acid. Fluorite naturally occurs on the earths' crust in rocks, coal and clay.

Preparation
Fluorine is normally made by electrolysis. Hydrogen fluoride is dissolved in potassium fluoride. This mixture is melted and an electric current is passed through it. This is electrolysis. Hydrogen is produced at one side and fluorine at the other side. If the sides are not separated, the cell may explode.

Someone made fluorine in 1986 without using electrolysis. They produced manganese(IV) fluoride by using various chemical compounds, which released fluorine gas.

Uses
Fluorine is used to enrich uranium for nuclear weapons. It is also used to make sulfur hexafluoride. Sulfur hexafluoride is used to propel stuff out of an aerosol can. It is also used to make integrated circuits. Fluorine compounds have many uses. Fluoride ions are in fluorine compounds. Fluoride ions can be in toothpaste. Some are used in nonstick coatings. Freons contain fluorine.

Safety
Fluorine as an element is extremely reactive and toxic. It can react with almost everything, even glass. Fluorine is also poisonous.

Fluoride ions are somewhat toxic. If too much toothpaste containing fluoride is eaten then fluoride poisoning may occur. Fluoride is not reactive, though.

Related pages
 :Category:Fluorine compounds
 List of common elements
 Halogen

Sources

Nonmetals
Halogens