Sulfur (also spelled sulphur in British English) 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 octatomic molecules with a 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 abundant 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". Today, 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.

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Atomic properties

Standard atomic weight32.06 ±0.02 [32.059 … 32.076]
Atomic mass32.0632 u

Atomic radii

Radius (empirical)100 pm
Radius (calculated)88 pm
Covalent radius105 ±3 pm
Van der Waals radius180 pm

Atomic shell

Electron configurationNe 3s2 3p4
Ionization energy(1st) 10.36001 eV
(2nd) 23.33788 eV
(3rd) 34.86 eV
(4th) 47.222 eV
(5th) 72.5945 eV
(6th) 88.0529 eV
Shell model

Physical properties

Density2.07 g·cm−3
Molar volume1.553·10-5 m3·mol−1


Melting point388.3 K
Boiling point717.8 K
Liquid range329.4 K
Critical point1,314 K @ 20.7 MPa
Transition temperature17 K


Melting enthalpy1.73 kJ·mol-1
Enthalpy of vaporization9.8 kJ·mol-1
Binding energy279 kJ·mol-1

Heat and conductivity

Specific heat capacity736 J·kg−1·K−1
Thermal conductivity0.205 W·m-1·K-1


Mohs hardness2

Elastic properties

Bulk modulus7.7 GPa

Electrical properties

Resistance1·1016 Ωm


Magnetic susceptibility-1.551·10-5 cm3·mol−1 (298 K)

Optical properties

Refractive index1.001

Chemical properties

Basicitystrongly acidic
Oxidation state±2 … +6
Standard potential-0.48 V (S + 2e- → S2-)


Pauling scale2.58
Sanderson scale2.96
Allred-Rochow scale2.44
Mulliken scale2.69
Allen scale2.589
Ghosh-Gupta scale6.837 eV
Boyd-Edgecombe scale2.64
Nagle scale2.49
Pearson absolute negativity6.22 eV

Other properties

Natural occurrenceprimordial
Crystal structureOrthorhombic
Goldschmidt Classificationchalcophile
Superconductorwith transition tempperature under special conditions
Price/kg0.0926 USD

Natural abundances

500,000 ppb ≈ 5.02·1015 M☉
400,000 ppb ≈ 7.95·1014 Mt
4.1·107 ppb ≈ 41 kg
Earth’s crust
420,000 ppb ≈ 1.16·107 Mt
928,000 ppb ≈ 1,270 Mt
Flowing water
4,000 ppb ≈ 64 Gt
Human body
2·106 ppb ≈ 140 g