Sulfur
[Ne] 3s² 3p⁴ · 2 · 8 · 6
A bright yellow nonmetal known since antiquity as brimstone. Sulfur forms more allotropes than any other element, and the sulfuric acid made from it is the largest-tonnage chemical in the world.
3D model
Bohr model: nucleus and electron shells from the real configuration. Valence electrons are highlighted.
Drag to rotate, scroll to zoom
Atomic properties
- Atomic number
- 16
- Atomic mass
- 32.06 а.е.м.
- Electron configuration
- [Ne] 3s² 3p⁴
- Electrons per shell
- 2 · 8 · 6
- Block
- p-block
- Group
- Chalcogens
- Period
- 3
- Electronegativity (Pauling)
- 2.58
- Electronegativity (Allen)
- 2.59
- Atomic radius
- 88 pm
- Covalent radius
- 105 pm
- Van der Waals radius
- 180 pm
- Ionisation energy 1
- 999.6 kJ/mol
- Ionisation energy 2
- 2 252 kJ/mol
- Ionisation energy 3
- 3 357 kJ/mol
- Ionisation energy 4
- 4 556 kJ/mol
- Ionisation energy 5
- 7 004.3 kJ/mol
- Electron affinity
- 200.4 kJ/mol
- Common oxidation states
- -2, +4, +6
- Oxidation states
- -2, -1, +1, +2, +3, +4, +5, +6
Physical properties
- State at 25 °C
- solid
- Density
- 2.07 g/cm³
- Melting point
- 388.36 K · 115.2 °C
- Boiling point
- 717.8 K · 444.7 °C
- Speed of sound
- no data
Thermal properties
- Heat of fusion
- 1.727 kJ/mol
- Heat of vaporisation
- 45 kJ/mol
- Specific heat capacity
- 0.71 J/(g·K)
- Thermal conductivity
- 0.205 W/(m·K)
Mechanical properties
- Young's modulus
- no data
- Shear modulus
- no data
- Bulk modulus
- 7.7 GPa
- Poisson ratio
- no data
- Mohs hardness
- 2
- Brinell hardness
- no data
Electrical and magnetic properties
- Electrical resistivity
- 2·10¹⁵ nΩ·m
- Magnetic ordering
- diamagnetic
- Curie point
- no data
- Néel point
- no data
- Superconducting point
- no data
Crystal structure
- Crystal structure
- orthorhombic
- Lattice constants
- a = 1 043.7 pm · b = 1 284.5 pm · c = 2 436.9 pm
Abundance
- In the crust
- 350 mg/kg
- In the ocean
- 905 mg/L
- In the universe
- 500 000 mg/kg
- In the human body
- 2 000 mg/kg
Isotopes
| Isotope | Abundance | Half-life | Decay mode |
|---|---|---|---|
| 32S | 94.99 % | stable | — |
| 33S | 0.75 % | stable | — |
| 34S | 4.25 % | stable | — |
| 36S | 0.01 % | stable | — |
The sulfur-34 to sulfur-32 ratio in sedimentary rock records the activity of sulfate-reducing bacteria and serves as a marker of early life.
Discovery
- Year of discovery
- known since antiquity
- Discovered by
- known since antiquity
- Where
- no data
- Origin of the name
- from Sanskrit sulvere and Latin sulphurium
History
Sulfur was used for fumigation and medicine long before written history, and appears in the Bible and in Chinese texts. Lavoisier proved in 1777 that it is an element rather than a compound.
Where it occurs
350 mg/kg of the crust, found native around volcanoes and bound as sulfides and sulfates. In the ocean sulfate is the second most abundant anion after chloride.
How it is produced
Almost all sulfur today is a by-product of desulfurising oil and gas by the Claus process. Frasch mining of native sulfur has essentially ceased.
Role in living things
Sulfur is in the amino acids cysteine and methionine, and the disulfide bridges between them set a protein's tertiary structure. They are what make hair and nails tough.
Safety
Sulfur itself is of low toxicity. Its compounds are not: hydrogen sulfide paralyses the sense of smell and kills faster than hydrogen cyanide, and sulfur dioxide produces acid rain.
Uses
- Sulfuric acid: fertiliser, metallurgy, refining — over 250 million tonnes a year
- Vulcanising rubber: sulfur cross-links the polymer chains and turns a sticky mass into rubber
- Fungicides and crop protection
- Black powder and pyrotechnics
- Sulfite pulping of wood
Curiosities
- The rotten-egg smell is hydrogen sulfide, not sulfur; sulfur itself barely smells at all.
- Sulfur has more than thirty allotropes, a record among the elements.
- Molten sulfur darkens and thickens on heating, then thins again — a rare viscosity anomaly.
- A country's sulfuric acid output was long taken as a measure of its industrial development.