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#1 2025-07-21 16:23:48

Jai Ganesh
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Registered: 2005-06-28
Posts: 51,538

Sulfur

Sulfur

Gist

Sulfur is a chemical element with the symbol S and atomic number 16. It is a bright yellow, crystalline solid at room temperature and is known for its pungent odor when burned. It is a nonmetal, abundant, and multivalent. Sulfur forms cyclic octatomic molecules with the formula S₈.

Sulfur (in British English, Sulphur) is a chemical element with the symbol S and atomic number 16. It is abundant, multivalent, and nonmetallic. Under normal conditions, sulfur atoms form cyclic octatonic molecules with a chemical formula S8.

Sulfur, also spelled sulphur, is a chemical element with the symbol S and atomic number 16. It's a bright yellow, brittle, nonmetallic solid at room temperature. Sulfur is known for its reactivity and its ability to form compounds with most elements. It's essential for life and is found in many animal and vegetable substances, especially proteins.

Summary

Sulfur (American spelling and the preferred IUPAC name) or sulphur (Commonwealth spelling) is a chemical element; it has symbol S and atomic number 16. It is abundant, multivalent and nonmetallic. Under normal conditions, sulfur atoms form cyclic octatomic molecules with the chemical formula S8. Elemental sulfur is a bright yellow, crystalline solid at room temperature.

Sulfur is the tenth most abundant element by mass in the universe and the fifth most common on Earth. Though sometimes found in pure, native form, sulfur on Earth usually occurs as sulfide and sulfate minerals. Being abundant in native form, sulfur was known in ancient times, being mentioned for its uses in ancient India, ancient Greece, China, and ancient Egypt. Historically and in literature sulfur is also called brimstone, which means "burning stone". Almost all elemental sulfur is produced as a byproduct of removing sulfur-containing contaminants from natural gas and petroleum. The greatest commercial use of the element is the production of sulfuric acid for sulfate and phosphate fertilizers, and other chemical processes. Sulfur is used in matches, insecticides, and fungicides. Many sulfur compounds are odoriferous, and the smells of odorized natural gas, skunk scent, bad breath, grapefruit, and garlic are due to organosulfur compounds. Hydrogen sulfide gives the characteristic odor to rotting eggs and other biological processes.

Sulfur is an essential element for all life, almost always in the form of organosulfur compounds or metal sulfides. Amino acids (two proteinogenic: cysteine and methionine, and many other non-coded: cystine, taurine, etc.) and two vitamins (biotin and thiamine) are organosulfur compounds crucial for life. Many cofactors also contain sulfur, including glutathione, and iron–sulfur proteins. Disulfides, S–S bonds, confer mechanical strength and insolubility of the (among others) protein keratin, found in outer skin, hair, and feathers. Sulfur is one of the core chemical elements needed for biochemical functioning and is an elemental macronutrient for all living organisms.

Details

Sulfur (S) is a nonmetallic chemical element belonging to the oxygen group (Group 16 [VIa] of the periodic table), one of the most reactive of the elements. Pure sulfur is a tasteless, odourless, brittle solid that is pale yellow in colour, a poor conductor of electricity, and insoluble in water. It reacts with all metals except gold and platinum, forming sulfides; it also forms compounds with several nonmetallic elements. Millions of tons of sulfur are produced each year, mostly for the manufacture of sulfuric acid, which is widely used in industry.

In cosmic abundance, sulfur ranks ninth among the elements, accounting for only one atom of every 20,000–30,000. Sulfur occurs in the uncombined state as well as in combination with other elements in rocks and minerals that are widely distributed, although it is classified among the minor constituents of Earth’s crust, in which its proportion is estimated to be between 0.03 and 0.06 percent. On the basis of the finding that certain meteorites contain about 12 percent sulfur, it has been suggested that deeper layers of Earth contain a much larger proportion. Seawater contains about 0.09 percent sulfur in the form of sulfate. In underground deposits of very pure sulfur that are present in domelike geologic structures, the sulfur is believed to have been formed by the action of bacteria upon the mineral anhydrite, in which sulfur is combined with oxygen and calcium. Deposits of sulfur in volcanic regions probably originated from gaseous hydrogen sulfide generated below the surface of Earth and transformed into sulfur by reaction with the oxygen in the air.

Element Properties

atomic number  :  16
atomic weight  :  32.064
melting point  :
rhombic  :  112.8 °C (235 °F)
monoclinic  :  119 °C (246 °F)

boiling point  :  444.6 °C (832 °F)

density (at 20 °C [68 °F])   
rhombic  :  2.07 grams/{cm}^{3}
monoclinic  :  1.96 grams/{cm}^{3}
oxidation states  :  −2, +4, +6

History

The history of sulfur is part of antiquity. The name itself probably found its way into Latin from the language of the Oscans, an ancient people who inhabited the region including Vesuvius, where sulfur deposits are widespread. Prehistoric humans used sulfur as a pigment for cave painting; one of the first recorded instances of the art of medication is in the use of sulfur as a tonic.

The combustion of sulfur had a role in Egyptian religious ceremonials as early as 4,000 years ago. “Fire and brimstone” references in the Bible are related to sulfur, suggesting that “hell’s fires” are fuelled by sulfur. The beginnings of practical and industrial uses of sulfur are credited to the Egyptians, who used sulfur dioxide for bleaching cotton as early as 1600 bce. Greek mythology includes sulfur chemistry: Homer tells of Odysseus’ use of sulfur dioxide to fumigate a chamber in which he had slain his wife’s suitors. The use of sulfur in explosives and fire displays dates to about 500 bce in China, and flame-producing agents used in warfare (Greek fire) were prepared with sulfur in the Middle Ages. Pliny the Elder in 50 ce reported a number of individual uses of sulfur and ironically was himself killed, in all probability by sulfur fumes, at the time of the great Vesuvius eruption (79 ce). Sulfur was regarded by the alchemists as the principle of combustibility. Antoine Lavoisier recognized it as an element in 1777, although it was considered by some to be a compound of hydrogen and oxygen; its elemental nature was established by the French chemists Joseph Gay-Lussac and Louis Thenard.

Natural occurrence and distribution

Many important metal ores are compounds of sulfur, either sulfides or sulfates. Some important examples are galena (lead sulfide, PbS), blende (zinc sulfide, ZnS), pyrite (iron disulfide, FeS2), chalcopyrite (copper iron sulfide, CuFeS2), gypsum (calcium sulfate dihydrate, CaSO4∙2H2O) and barite (barium sulfate, BaSO4). The sulfide ores are valued chiefly for their metal content, although a process developed in the 18th century for making sulfuric acid utilized sulfur dioxide obtained by burning pyrite. Coal, petroleum, and natural gas contain sulfur compounds.

Allotropy

In sulfur, allotropy arises from two sources: (1) the different modes of bonding atoms into a single molecule and (2) packing of polyatomic sulfur molecules into different crystalline and amorphous forms. Some 30 allotropic forms of sulfur have been reported, but some of these probably represent mixtures. Only eight of the 30 seem to be unique; five contain rings of sulfur atoms and the others contain chains.

In the rhombohedral allotrope, designated ρ-sulfur, the molecules are composed of rings of six sulfur atoms. This form is prepared by treating sodium thiosulfate with cold, concentrated hydrochloric acid, extracting the residue with toluene, and evaporating the solution to give hexagonal crystals. ρ-sulfur is unstable, eventually reverting to orthorhombic sulfur (α-sulfur).

A second general allotropic class of sulfur is that of the eight-membered ring molecules, three crystalline forms of which have been well characterized. One is the orthorhombic (often improperly called rhombic) form, α-sulfur. It is stable at temperatures below 96 °C (204.8 °F). Another of the crystalline S8 ring allotropes is the monoclinic or β-form, in which two of the axes of the crystal are perpendicular, but the third forms an oblique angle with the first two. There are still some uncertainties concerning its structure; this modification is stable from 96 °C to the melting point, 118.9 °C (246 °F). A second monoclinic cyclooctasulfur allotrope is the γ-form, unstable at all temperatures, quickly transforming to α-sulfur.

An orthorhombic modification, S12 ring molecules, and still another unstable S10 ring allotrope are reported. The latter reverts to polymeric sulfur and S8. At temperatures above 96 °C (204.8 °F), the α-allotrope changes into the β-allotrope. If enough time is allowed for this transition to occur completely, further heating causes melting to occur at 118.9 °C (246 °F); but if the α-form is heated so rapidly that the transformation to β-form does not have time to occur, the α-form melts at 112.8 °C (235 °F).

Just above its melting point, sulfur is a yellow, transparent, mobile liquid. Upon further heating, the viscosity of the liquid decreases gradually to a minimum at about 157 °C (314.6 °F), but then rapidly increases, reaching a maximum value at about 187 °C (368.6 °F); between this temperature and the boiling point of 444.6 °C (832.3 °F), the viscosity decreases. The colour also changes, deepening from yellow through dark red, and, finally, to black at about 250 °C (482 °F). The variations in both colour and viscosity are considered to result from changes in the molecular structure. A decrease in viscosity as temperature increases is typical of liquids, but the increase in the viscosity of sulfur above 157 °C probably is caused by rupturing of the eight-membered rings of sulfur atoms to form reactive S8 units that join together in long chains containing many thousands of atoms. The liquid then assumes the high viscosity characteristic of such structures. At a sufficiently high temperature, all of the cyclic molecules are broken, and the length of the chains reaches a maximum. Beyond that temperature, the chains break down into small fragments. Upon vaporization, cyclic molecules (S8 and S6) are formed again; at about 900 °C (1,652 °F), S2 is the predominant form; finally, monatomic sulfur is formed at temperatures above 1,800 °C (3,272 °F).

Additional Information:

Appearance

There are several allotropes of sulfur. The most common appears as yellow crystals or powder.

Uses

Sulfur is used in the vulcanisation of black rubber, as a fungicide and in black gunpowder. Most sulfur is, however, used in the production of sulfuric acid, which is perhaps the most important chemical manufactured by western civilisations. The most important of sulfuric acid’s many uses is in the manufacture of phosphoric acid, to make phosphates for fertilisers.

Mercaptans are a family of organosulfur compounds. Some are added to natural gas supplies because of their distinctive smell, so that gas leaks can be detected easily. Others are used in silver polish, and in the production of pesticides and herbicides.

Sulfites are used to bleach paper and as preservatives for many foodstuffs. Many surfactants and detergents are sulfate derivatives. Calcium sulfate (gypsum) is mined on the scale of 100 million tonnes each year for use in cement and plaster.

Biological role

Sulfur is essential to all living things. It is taken up as sulfate from the soil (or seawater) by plants and algae. It is used to make two of the essential amino acids needed to make proteins. It is also needed in some co-enzymes. The average human contains 140 grams and takes in about 1 gram a day, mainly in proteins.

Sulfur and sulfate are non-toxic. However, carbon disulfide, hydrogen sulfide and sulfur dioxide are all toxic. Hydrogen sulfide is particularly dangerous and can cause death by respiratory paralysis.

Sulfur dioxide is produced when coal and unpurified oil are burned. Sulfur dioxide in the atmosphere causes acid rain. This can cause lakes to die, partly by making toxic aluminium salts soluble, so that they are taken up by living things.

Natural abundance

Sulfur occurs naturally as the element, often in volcanic areas. This has traditionally been a major source for human use. It is also widely found in many minerals including iron pyrites, galena, gypsum and Epsom salts.

Elemental sulfur was once commercially recovered from wells by the Frasch process. This involved forcing super-heated steam into the underground deposits to melt the sulfur, so it could be pumped to the surface as a liquid.

Modern sulfur production is almost entirely from the various purification processes used to remove sulfur from natural gas, oil and tar sands. All living things contain sulfur and when fossilised (as in fossil fuels) the sulfur remains present. If unpurified fossil fuels are burnt, sulfur dioxide can enter the atmosphere, leading to acid rain.

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