Sulfur (or sulphur) is a chemical element. The symbol for sulfur is S, and its atomic number is 16.

Properties
Sulfur is a yellow solid that is a nonmetal. It is fragile (easily broken) and crystalline. It burns easily, releasing toxic fumes of sulfur dioxide. It has a very faint odor. If it is melted and cooled very quickly, it makes a rubbery form of sulfur that is called "plastic sulfur". It gradually turns back into the yellow brittle form. It does not dissolve in water. The smell normally known as "sulfur" comes from hydrogen sulfide and similar chemicals. These sulfides are produced when things decay without air.

Chemical compounds
Sulfur compounds are chemical compounds containing sulfur ions. Sulfur comes in several forms: oxidation states of -2 (hydrogen sulfide), +4 (sulfur dioxide, sulfites) and +6 (sulfuric acid, sulfates) are most common, although there are other oxidation states.

Sulfur oxides

Sulfur dioxide, colorless toxic heavy gas, used to preserve dried foods
Sulfur trioxide, various forms, sometimes liquid, irritating and toxic
Oleum, sulfur trioxide dissolved in sulfuric acid

Sulfur acids
Mixture of sulfur oxides and water
Sulfurous acid, unstable, weak
Sulfuric acid, stable, strong acid, most used chemical after water
Hydrogen sulfate, an ion produced when sulfuric acid only loses one acidic proton
Hydrogen sulfide, weak smelly gas, becomes acidic when dissolved in water

Sulfides

Salts of hydrogen sulfide
Ammonium sulfide, used in stink bombs
Antimony trisulfide, used in match heads
Arsenic trisulfide, less toxic arsenic compound
Barium sulfide, used to make barium from barium sulfate
Bismuth(III) sulfide, bismuth ore
Iron sulfide, found as pyrite naturally
Lead(II) sulfide, found as galena naturally
Selenium disulfide, used in hair treatment creams
Potassium sulfide, reacts with water
Silver sulfide, tarnish on silver objects
Thallium(I) sulfide, infrared detector
Tin(II) sulfide, dark brown solid
Tin(IV) sulfide, gold solid, "mosaic gold"
Zinc sulfide, used in fluorescent bulbs

Sulfites

Salts of sulfurous acid
Sodium sulfite, used to preserve dried foods
Potassium sulfite, used to preserve foods

Sulfates and bisulfates

Salts of sulfuric acid
Alums, all of them
Aluminium sulfate
Ammonium sulfate, used in fertilizers
Barium sulfate, used to take X-rays of digestive system
Cobalt(II) sulfate, used in pigments
Copper(II) sulfate, used to kill algae
Chromium sulfate, used to make chrome alum
Iron(II) sulfate, used for reduction 
Iron(III) sulfate, rare
Lead(II) sulfate, white solid in lead acid batteries
Manganese(II) sulfate, used to add manganese to soil
Nickel(II) sulfate, used to make nickel compounds
Sodium bisulfate, used in lowering pH
Sodium sulfate, used in detergents and paper making
Thallium(I) sulfate, colorless odorless tasteless highly toxic
Tin(II) sulfate, used to make other tin compounds
Zinc sulfate, used in pigments

Other sulfur compounds
Sulfur(I) compounds
Sulfur(I) chloride, yellow liquid

Sulfur(II) compounds
Sulfur(II) chloride, red odorous liquid

Sulfur(III) compounds
Disulfur dinitride, colorless solid
Tetrasulfur tetranitride, orange solid

Sulfur(IV) compounds
Sulfur tetrafluoride, colorless toxic gas

Sulfur(V) compounds
Disulfur decafluoride, colorless toxic liquid

Sulfur(VI) compounds
Sulfur hexafluoride, colorless heavy gas

Occurrence and preparation

Sulfur can be found in the earth near volcanoes. Many minerals contain sulfur ions. Coal contains sulfur ions which are released when it burns. Hydrogen sulfide and sulfur dioxide are some sulfur compounds that are released when coal burns. They are reacted to make sulfur. Sulfur in the ground in melted, then forced up through pipes by compressed (squeezed) air.

Uses
Sulfur is commonly used in gunpowder, medicine, and matches. Matches release sulfur dioxide when they burn, giving them their smell. Sulfur is an essential component to living cells. Many proteins contain sulfur. It is also used as a pesticide on organic farms.

Etymology
Powder sulfur is said to be left after an occurrence of a supernatural being.

Toxicity and safety
Sulfur is not toxic, but the chemical compounds formed when sulfur burns can be very toxic. Sulfuric acid, for example, can make paper turn black!

History
The ancient name for sulfur is brimstone. Sulfur was used in fumigation (making fumes) and medicine in ancient Greece. In 1777, Antoine Lavosier convinced the scientific community that sulfur was an element.

Related pages
 Periodic table
 List of common elements
 Sulfur compounds

Other websites 
 WebElements.com – Sulfur
 EnvironmentalChemistry.com – Sulfur

Chemical elements
Nonmetals