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Sulfur or sulphur (IPA: /ˈsʌlfə(ɹ)/, see spelling below) is the chemical element that has the symbol S and atomic number 16. It is an abundant, tasteless, odorless, multivalent non-metal. more...
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Sulfur, in its native form, is a yellow crystalline solid. In nature, it can be found as the pure element or as sulfide and sulfate minerals. It is an essential element for life and is found in two amino acids, cysteine and methionine. Its commercial uses are primarily in fertilizers, but it is also widely used in gunpowder, matches, insecticides and fungicides.
Notable characteristics
At room temperature, sulfur is a soft bright yellow solid. Elemental sulfur has only a faint odor similar to that of matches. The odor associated with rotten eggs is from hydrogen sulfide (H2S) and organic sulfur compounds. Sulfur burns with a blue flame that emits sulfur dioxide, notable for its peculiar suffocating odor. Sulfur is insoluble in water but soluble in carbon disulfide and to a lesser extent in other organic solvents such as benzene. Common oxidation states of sulfur include −2, +2, +4 and +6. Sulfur forms stable compounds with all elements except the noble gases.
Sulfur in the solid state ordinarily exists as cyclic crown-shaped S8 molecules. Sulfur has many allotropes besides S8. Removing one atom from the crown gives S7, which is responsible for sulfur's distinctive yellow color. Many other rings have been prepared, including S12 and S18. By contrast, its lighter neighbor oxygen only exists in two states of allotropic significance: O2 and O3. Selenium, the heavier analogue of sulfur can form rings but is more often found as a polymer chain.
The crystallography of sulfur is complex. Depending on the specific conditions, the sulfur allotropes form several distinct crystal structures, with rhombic and monoclinic S8 best known.
A noteworthy property of sulfur is that its viscosity in its molten state, unlike most other liquids, increases above temperatures of 200°C due to the formation of polymer chains. The molten sulfur also becomes dark red in colour above this temperature due to the presence of free valences on terminal atoms of the polymer chains. However, after a specific temperature is reached, the viscosity is reduced because there is enough energy to break the chains.
Amorphous or "plastic" sulfur can be produced through the rapid cooling of molten sulfur. X-ray crystallography studies show that the amorphous form may have a helical structure with eight atoms per turn. This form is metastable at room temperature and gradually reverts back to crystalline form. This process happens within a matter of hours to days but can be rapidly catalyzed.
Applications
Sulfur has many industrial uses. Through its major derivative, sulfuric acid (H2SO4), sulfur ranks as one of the more important industrial raw materials. It is of prime importance to every sector of the world's economies.
Read more at Wikipedia.org
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