16 S Sulfur 32.06
Nonmetal p-block Period 3 Group 16

Sulfur

S · Element 16 · Chalcogens

Yellow, brittle, and responsible for the smell of struck matches, rotten eggs and volcanic vents.

STATE AT 20°C Solid
ATOMIC MASS 32.06 u
ELECTRON CONFIGURATION [Ne] 3s² 3p⁴

Structure

The sulfur atom

Not a diagram of dots on rings — a Monte-Carlo sample of the actual probability density |ψ|² for each occupied subshell. Drag to rotate. Blue and violet mark opposite signs of the wavefunction, which is what makes bonding possible.

Orbital cloud

Measured values

Property sheet

Every bar shows where sulfur sits among all 118 elements for that property.

Physical

Density 2.067 g/cm³ 18%
Melting point 388.4 K 22%
Boiling point 717.8 K 18%
Specific heat 0.71 J/g·K
Thermal conductivity 0.21 W/m·K 14%

Atomic

Atomic radius 105 pm 9%
Covalent radius 105 pm
Van der Waals radius 180 pm

Electronic

Electronegativity 2.58 92%
Ionisation energy 999.6 kJ/mol 85%
Electron affinity 200.7 kJ/mol 92%

Occurrence

Abundance in crust 350 mg/kg 86%

Identity

SymbolS
Atomic number16
Atomic mass32.06 u
CategoryNonmetal
Blockp
Crystal structureorthorhombic
Oxidation states-2, -1, +1, +2, +3, +4, +5, +6
DiscoveredPrehistoric
Discovered byKnown since antiquity

Sources: IUPAC 2021 standard atomic weights · CRC Handbook of Chemistry and Physics · NIST. Values marked ~ are predicted rather than measured.

Size, to scale

How big is a sulfur atom?

Radius 105 pm — that is 0.105 nm, so about 4762 million of them side by side would span a millimetre.

Thermal range

Solid, liquid, gas — and when

Sulfur is liquid over a 329 K window, from 388 K to 718 K.

Where it sits

Position in the table

Sulfur sits in period 3, group 16. Everything in group 16 shares the same outer-electron count, which is why they behave so similarly.

OTHER NONMETALS

All nonmetals

The story

What sulfur is, and how we found it

Yellow solid with distinctive smell. Essential for proteins.

The discovery of sulfur

The Discovery and History of Sulfur

Ancient Knowledge and Early Uses

Sulfur holds the distinction of being one of the few elements known to ancient civilizations in its pure form. Chinese alchemists around 500 BCE called it "liu huang" (flowing yellow) and used it in early gunpowder formulations. The ancient Egyptians employed sulfur for mummification and medicine, while Greek philosopher Pliny the Elder (23-79 CE) documented its use for fumigation and medicinal purposes in his "Natural History."

The element's name derives from the Latin "sulfurium," related to "sulfur" meaning "to burn." Ancient Romans knew it as "sulphur" and associated it with volcanic activity, particularly around Mount Vesuvius and the volcanic islands of Sicily.

Medieval Islamic Contributions

Jabir ibn Hayyan (721-815 CE), the father of chemistry, identified sulfur as one of the fundamental principles of matter in his sulfur-mercury theory. This Persian polymath proposed that all metals contained varying proportions of sulfur and mercury, a theory that dominated alchemical thinking for centuries. His work "Kitab al-Khawass al-kabir" described sulfur's properties and purification methods.

Antoine Lavoisier's significant Classification

The modern understanding of sulfur began with Antoine Laurent Lavoisier (1743-1794), who definitively proved sulfur was an element in his groundbreaking 1777 experiments. Working in his laboratory at the Paris Arsenal, Lavoisier demonstrated that sulfur could not be decomposed into simpler substances and included it in his famous 1789 list of 33 elements in "Traité Élémentaire de Chimie."

Lavoisier's student Joseph Louis Gay-Lussac (1778-1850) and colleague Louis Jacques Thénard (1777-1857) further confirmed sulfur's elemental nature in 1809 by showing that hydrogen sulfide contained only hydrogen and sulfur, with no hidden components.

Industrial Revolution and the Contact Process

The industrial significance of sulfur exploded during the 19th century. Peregrine Phillips, a British vinegar manufacturer, patented the Contact Process for sulfuric acid production on October 15, 1831. His method used platinum catalysts to efficiently convert sulfur dioxide to sulfur trioxide, revolutionizing chemical manufacturing.

Nicolas Leblanc (1742-1806) had earlier developed the Leblanc process in 1791, which required enormous quantities of sulfuric acid for sodium carbonate production, driving demand for sulfur worldwide.

The Frasch Process Revolution

German-American chemist Herman Frasch (1851-1914) solved the challenge of extracting sulfur from underground deposits with his ingenious process patented in 1894. Working for Union Sulfur Company in Louisiana, Frasch developed a method using superheated water (160°C) to melt underground sulfur and compressed air to force it to the surface.

On December 26, 1894, at Sulphur Mine, Louisiana, the first Frasch well produced molten sulfur, transforming the global sulfur industry. By 1900, American sulfur production had increased 100-fold, making the United States the world's leading sulfur producer.

Modern Sulfur Science

Eilhard Mitscherlich (1794-1863) discovered sulfur's allotropic forms in 1823, identifying rhombic and monoclinic crystals. Swedish chemist Jöns Jacob Berzelius (1779-1848) determined sulfur's atomic weight as 32.07 in 1818, remarkably close to today's accepted value of 32.065.

The 20th century brought understanding of sulfur's role in biochemistry, with Frederick Gowland Hopkins discovering the sulfur-containing amino acids cysteine and methionine, earning him the 1929 Nobel Prize in Physiology.

Applications

What sulfur is used for

Industrial Applications of Sulfur

Sulfuric Acid Production (85% of sulfur use)

Sulfur is primarily converted to sulfuric acid (H₂SO₄) through the Contact Process, invented by Peregrine Phillips in 1831. This three-stage process involves:

  • Stage 1: Sulfur burning in air to form sulfur dioxide (S + O₂ → SO₂)
  • Stage 2: Catalytic oxidation using vanadium pentoxide at 450°C (2SO₂ + O₂ → 2SO₃)
  • Stage 3: Absorption in concentrated sulfuric acid to prevent acid mist formation

Modern plants produce up to 3,000 tons per day, with 99.5% conversion efficiency. The largest producers include Mosaic Company (Florida) and Nutrien (Canada).

Fertilizer Manufacturing

Sulfuric acid is essential for producing phosphate fertilizers like superphosphate and triple superphosphate. The reaction Ca₃(PO₄)₂ + 2H₂SO₄ → Ca(H₂PO₄)₂ + 2CaSO₄ creates water-soluble phosphorus. Cargill and CF Industries operate massive sulfur-to-fertilizer facilities across the American Midwest.

Petroleum Refining

Sulfuric acid removes impurities in petroleum refining through alkylation processes. ExxonMobil and Chevron use 40-60% sulfuric acid to catalyze the combination of isobutane with alkenes, producing high-octane gasoline components. A single refinery consumes 200-500 tons of sulfuric acid daily.

Metal Processing and Mining

Sulfuric acid leaches copper from low-grade ores through heap leaching. At Freeport-McMoRan's Arizona operations, crushed ore is irrigated with dilute sulfuric acid (pH 1.5-2.0), dissolving copper as copper sulfate. This process recovers 60-90% of copper from ores containing only 0.4-0.8% copper.

Chemical Manufacturing

Sulfur compounds are crucial intermediates:

  • Sulfur dioxide (SO₂): Food preservative (E220) and wine antiseptic
  • Carbon disulfide (CS₂): Viscose rayon production at Lenzing AG facilities
  • Hydrogen sulfide (H₂S): Source for pure sulfur via Claus process in oil refineries
  • Sulfur chlorides: Rubber vulcanization accelerators

Rubber Vulcanization

Charles Goodyear's 1839 discovery uses elemental sulfur to cross-link rubber polymers. Modern tire manufacturing at Bridgestone and Michelin uses 1-3% sulfur by weight, creating disulfide bonds between polymer chains. This process transforms soft rubber into durable, elastic material resistant to temperature extremes.

Everyday Applications of Sulfur

Agricultural Products

  • Garden sulfur powder - Soil pH reduction for acid-loving plants like blueberries and azaleas
  • Sulfate fertilizers - Ammonium sulfate (21-0-0-24S) from manufacturers like Simplot
  • Fungicide sprays - Organic sulfur dusts for powdery mildew control on grapes and roses
  • Livestock supplements - Sulfur blocks for cattle to prevent mineral deficiency

Personal Care and Health

  • Acne treatments - Sulfur soaps and creams (brands: De La Cruz, Grisi)
  • Dandruff shampoos - Selenium sulfide in Head & Shoulders Clinical Strength
  • Arthritis medications - MSM (methylsulfonylmethane) supplements
  • Skin conditions - Sulfur ointments for seborrheic dermatitis and rosacea

Food and Beverages

  • Wine preservation - Sulfur dioxide (SO₂) prevents oxidation and bacterial growth
  • Dried fruits - Sulfites in apricots, raisins maintain color and freshness
  • Food processing - Potassium metabisulfite as antimicrobial agent
  • Beer brewing - Sulfur compounds create Campden tablets for sanitization

Household and Industrial

  • Matches - Sulfur in strike-anywhere match heads and safety match strips
  • Gunpowder - Traditional black powder (75% saltpeter, 15% charcoal, 10% sulfur)
  • Paper production - Sulfite pulping process at International Paper mills
  • Photography - Silver sulfide toners for artistic black and white prints
  • Concrete - Sulfur concrete for chemical-resistant construction applications

Automotive and Transportation

  • Tire manufacturing - Vulcanization agent in all rubber tires
  • Battery acid - Sulfuric acid electrolyte in lead-acid car batteries
  • Fuel additives - Organo-sulfur compounds improve fuel stability
  • Brake fluid - Sulfur compounds in DOT 3 and DOT 4 formulations

Where it comes from

Natural occurrence

350 mg/kg of Earth's crust · more abundant than 86% of elements

Natural Occurrence of Sulfur

Terrestrial Abundance

Sulfur ranks as the 10th most abundant element in the Earth's crust at 260 ppm, and the 5th most abundant in the human body. The element concentrates in specific geological environments due to its unique chemical properties and biological cycling.

Elemental Sulfur Deposits

Pure sulfur crystals form through several geological processes:

  • Volcanic regions: Mount Vesuvius (Italy), Kawah Ijen (Indonesia), and Yellowstone (USA) contain native sulfur from hydrogen sulfide oxidation
  • Salt domes: Texas and Louisiana Gulf Coast feature massive sulfur deposits up to 150 meters thick, formed by bacterial reduction of gypsum
  • Hot springs: Sulfur precipitates when hydrogen sulfide-rich water contacts oxygen at Rotorua (New Zealand) and Mammoth Hot Springs

Sulfur Minerals

Over 200 sulfur-bearing minerals exist in nature:

  • Pyrite (FeS₂): "Fool's gold" - most common sulfur mineral, found worldwide
  • Galena (PbS): Primary lead ore, major deposits in Missouri, Australia, Peru
  • Sphalerite (ZnS): Principal zinc ore, abundant in Mississippi Valley-type deposits
  • Chalcopyrite (CuFeS₂): Most important copper ore, found in porphyry deposits
  • Gypsum (CaSO₄·2H₂O): Evaporite mineral forming massive beds in sedimentary rocks
  • Anhydrite (CaSO₄): Forms when gypsum dehydrates at depth

Biological Sulfur Cycle

Sulfur undergoes complex transformations through biological processes:

  • Marine environments: Phytoplankton produce dimethyl sulfide (DMS), affecting cloud formation and climate
  • Soil ecosystems: Sulfur-reducing bacteria convert sulfates to hydrogen sulfide in anaerobic conditions
  • Hot springs bacteria: Thermophilic organisms like Sulfolobus oxidize sulfur at temperatures exceeding 80°C
  • Plant metabolism: Cruciferous vegetables (broccoli, garlic) concentrate organosulfur compounds

Cosmic and Stellar Origins

Sulfur forms through silicon burning in massive stars (>8 solar masses) at temperatures exceeding 3 billion Kelvin. The process: ²⁸Si + ⁴He → ³²S occurs during the final stages of stellar evolution. Sulfur-16 has a "magic number" of protons, making it unusually stable. Meteorites contain sulfur as troilite (FeS) and oldhamite (CaS), providing evidence of early solar system chemistry.

Ocean Chemistry

Seawater contains approximately 905 ppm sulfur as sulfate ions (SO₄²⁻), making it the second most abundant anion after chloride. Mid-ocean ridge hydrothermal vents deposit sulfur minerals from reaction of hot volcanic fluids with cold seawater, creating "black smoker" chimneys rich in copper, zinc, and lead sulfides.

Handling

Safety

Sulfur Safety Information

Toxicity and Health Hazards

Elemental sulfur has remarkably low toxicity with an oral LD50 of >5,000 mg/kg in rats, making it practically low-toxicity. However, sulfur compounds pose significant hazards:

  • Hydrogen sulfide (H₂S): Extremely toxic gas, fatal at 500-1000 ppm within minutes
  • Sulfur dioxide (SO₂): Respiratory irritant, OSHA limit 5 ppm (8-hour TWA)
  • Carbon disulfide (CS₂): Neurotoxin affecting central nervous system, OSHA limit 20 ppm

OSHA Regulations and Exposure Limits

  • Elemental sulfur dust: 15 mg/m³ total dust, 5 mg/m³ respirable fraction
  • Sulfuric acid: 1 mg/m³ (8-hour TWA), immediate danger level 15 mg/m³
  • Hydrogen sulfide: 10 ppm ceiling limit, 50 ppm maximum peak for 10 minutes

Personal Protective Equipment (PPE)

  • Respiratory protection: N95 masks for sulfur dust, supplied air for H₂S environments
  • Eye protection: Safety goggles when handling sulfur compounds
  • Skin protection: Nitrile gloves, chemical-resistant clothing for acids
  • Foot protection: Chemical-resistant boots in industrial settings

Safe Handling and Storage

Elemental sulfur: Store in cool, dry areas away from oxidizers. Sulfur dust can create explosion hazards - maintain humidity above 65% and use anti-static equipment. Ground all containers and avoid friction-generating activities.

Sulfuric acid: Store in double-walled containers, maintain temperature below 40°C. Always add acid to water, never water to acid. Provide emergency eyewash stations within 25 feet of storage areas.

Emergency Procedures

  • Skin contact with sulfuric acid: Flush immediately with water for 15+ minutes, remove contaminated clothing
  • Eye exposure: Rinse with water for 15+ minutes, seek immediate medical attention
  • Hydrogen sulfide exposure: Move to fresh air immediately, provide oxygen if available, call emergency services
  • Ingestion: Do not induce vomiting for acids, give water if conscious, seek medical attention

Fire and Explosion Hazards

Sulfur burns at 248°C producing toxic sulfur dioxide. Sulfur dust can form explosive mixtures in air (35-1400 g/m³). Use water spray to cool burning sulfur, never use CO₂ or dry chemical extinguishers on large sulfur fires.

Quick answers

Sulfur: common questions

What is Sulfur?

Sulfur (symbol S) is element 16 on the periodic table, a nonmetal in period 3, group 16. Yellow, brittle, and responsible for the smell of struck matches, rotten eggs and volcanic vents. At room temperature it is a solid.

What is the electron configuration of Sulfur?

Sulfur's ground-state electron configuration is [Ne] 3s² 3p⁴, giving 3 occupied shells holding 2, 8, 6 electrons respectively. Its outer shell holds 6 electrons, which is what sets its bonding behaviour.

What are the melting and boiling points of Sulfur?

Sulfur melts at 388.4 K (115.2 °C) and boils at 717.8 K (444.7 °C).

What is the atomic mass of Sulfur?

The standard atomic weight of Sulfur is 32.06 u. That is a weighted average across its naturally occurring isotopes, which is why it is rarely a whole number.

How dense is Sulfur?

Sulfur has a density of 2.067 g/cm³. Water is 1.0 g/cm³, so a block of sulfur is about 2.1× heavier.

What is the electronegativity of Sulfur?

Sulfur has a Pauling electronegativity of 2.58. The scale runs from 0.70 (francium, the least greedy for electrons) to 3.98 (fluorine, the most). Values in this middle band tend to form covalent rather than strongly ionic bonds.

Who discovered Sulfur, and when?

Sulfur has been known since antiquity — it occurs in a form usable without smelting, so no single person can be credited with its discovery. The name comes from sanskrit sulvere, via Latin sulphurium.

How common is Sulfur on Earth?

Sulfur makes up about 350 mg/kg of the Earth's crust — common enough to be mined at scale.