sulfur

sulfur
Number	16
Name	sulfur
Pronunciation	ˈ, s, ʌ, l, f, ər SUL, fər
Standard atomic weight	32.06
Category	polyatomic nonmetal
Group	16
Electron configuration	[Ne] 3s2 3p4
Electrons per shell	2, 8, 6
Phase	solid
Density gpcm3	(alpha) 2.07, (beta) 1.96
Melting point K	388.36
Boiling point K	717.8
Triple point K	368.7
Triple point kpa	0.2
Critical point K	1314
Critical point mpa	20.7
Heat fusion	(monoclinic) 1.727
Heat vaporization	(monoclinic) 45
Molar heat capacity	22.75
Vapor pressure 1	375
Vapor pressure 10	408
Vapor pressure 100	449
Vapor pressure 1k	508
Vapor pressure 10k	591
Vapor pressure 100k	717
Oxidation states	−2, −1, 0, +1, +2, +3, +4, +5, +6
Electronegativity	2.58
Ionization energies1	999.6
Ionization energies2	2252
Ionization energies3	3357
Ionization energies4	4556
Ionization energies5	7004.3
Ionization energies6	8495.8
Atomic radius	100
Covalent radius	105±3
Van der Waals radius	180
Crystal structure	orthorhombic
Thermal conductivity	0.205
Magnetic ordering	diamagnetic
CAS number	7704-34-9

sulfur. It is a multivalent, abundant nonmetal found in Group 16 of the periodic table, characterized by its bright yellow color in its most common form. Known since antiquity, it is an essential element for all life and is a key component in many industrial and chemical processes. Its chemical symbol is S, and its atomic number is 16.

Properties

At room temperature, sulfur is a brittle solid that exists in several allotropic forms, with orthorhombic α-sulfur being the most stable. When heated, it melts into a mobile, amber-colored liquid that becomes viscous and dark red at higher temperatures due to the formation of polymeric chains. It is a poor conductor of electricity and heat, and it burns with a characteristic blue flame to form sulfur dioxide, a pungent gas. Notable physical characteristics include its low melting point and its insolubility in water but solubility in carbon disulfide.

Occurrence and production

Sulfur occurs natively in volcanic regions such as Sicily, Indonesia, and Japan, and in extensive underground deposits formed by anaerobic bacteria, like those in the Gulf of Mexico. Major production comes from the Frasch process, which uses superheated water to extract it from salt domes, particularly in the United States. It is also recovered as a byproduct from the purification of natural gas and petroleum at facilities like those in Alberta and the Middle East, and from metal sulfide ores such as pyrite and chalcopyrite during smelting operations.

Compounds

Sulfur forms a vast array of compounds, most notably hydrogen sulfide, a toxic gas with a rotten egg odor, and sulfur dioxide, a major air pollutant and precursor to acid rain. Important classes include sulfuric acid, a cornerstone of the chemical industry produced via the Contact process, and various sulfate salts like gypsum and Epsom salts. In organic chemistry, it is found in compounds such as the amino acids cysteine and methionine, and in functional groups like thiols and disulfide bonds critical to protein structure.

Applications

The primary use of sulfur is in the production of sulfuric acid, vital for manufacturing fertilizers like ammonium sulfate and superphosphate, and for processing minerals like copper and zinc. It is a key component in vulcanization, a process discovered by Charles Goodyear that strengthens rubber. Other applications include its use in fungicides, insecticides, and matches, in the production of sulfite pulp for paper, and in gunpowder and fireworks.

Biological role

Sulfur is an essential element for all living cells, being a component of the amino acids cysteine and methionine, and thus of many proteins and enzymes. It is crucial in coenzymes like coenzyme A and biotin, and in the antioxidant glutathione. Disulfide bonds between cysteine residues provide structural stability in proteins, such as those found in keratin in hair and feathers. Certain archaea and bacteria in environments like hydrothermal vents utilize sulfur compounds in their metabolism.

History

Known in ancient times, sulfur is referred to in the Bible as brimstone and was used by cultures such as the Egyptians for fumigation and in Greek fire. Alchemists considered it one of the three principle substances. Its elemental nature was recognized by Antoine Lavoisier in the late 18th century. The development of the Frasch process by Herman Frasch in the 1890s revolutionized its mining, and its critical role in industrial chemistry was cemented with the large-scale production of sulfuric acid during the Industrial Revolution.

Category:Chemical elements Category:Nonmetals