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Sulfur (S)

Sulfur (symbol S) is the chemical element with atomic number 16: a nonmetal, solid at 0 °C, with an atomic mass of 32.06 u. Known since antiquity.

Sulfur is a bright yellow solid known since antiquity, associated with volcanoes and, in tradition, with hell. The rotten-egg smell blamed on it actually comes from its compounds, such as hydrogen sulfide. Turned into sulfuric acid, the most-produced chemical in the world, it goes into fertilizers, batteries and countless processes. It is also present in our proteins and our hair.

Key facts

Atomic number
16
Symbol
S
French name
Soufre
Atomic mass
32.06 u
Molar mass
32.06 g/mol
Family
Nonmetals
Position
period 3, group 16, p-block
State at 0 °C
Solid
Melting point
115.2 °C
Boiling point
444.7 °C
Density
2.07 g/cm³
Electronegativity (Pauling)
2.58
First ionization energy
1,000 kJ/mol
Atomic radius
100 pm
Electron configuration
[Ne] 3s² 3p⁴
Abundance in Earth's crust
350 ppm (16th most abundant element)
Indicative price
0.09 $/kg (order of magnitude)
Radioactive
no
Discovery
Antiquity

Origin of the name

From the Latin sulfur.

What does sulfur look like?

Bright lemon-yellow crystals or powder, odorless when pure. When melted, it becomes an orange and then dark red liquid, and it burns with a blue flame.

Where is sulfur found?

About 0.04% of Earth's crust. It occurs in native form around volcanoes, and above all combined in metal sulfides, gypsum, oil and natural gas. The human body contains about 140 g.

Natural sources

  • Native sulfur
  • Pyrite
  • Gypsum
  • Galena
  • Sphalerite

How is sulfur produced?

Today, most sulfur (about 80 million tonnes a year) is recovered when oil and natural gas are desulfurized. In the past, it was extracted from underground deposits by melting it with superheated water (Frasch process). It is then burned to make about 250 million tonnes of sulfuric acid a year.

Top producers

  • China
  • United States
  • Russia
  • Saudi Arabia
  • United Arab Emirates

What is sulfur used for?

  • Sulfuric acid for phosphate fertilizers.
  • Vulcanizing tire rubber.
  • Fungicide treatment for grapevines.
  • Electrolyte in lead-acid batteries.
  • Preserving wine (sulfites) and dried fruit.

In everyday life

  • Your car's tires
  • The car battery
  • The “contains sulfites” label on a wine bottle
  • The smell of a match being struck

Role in living things

Essential: it is part of two amino acids (cysteine and methionine). Disulfide bridges, bonds between two sulfur atoms, give proteins their shape and hair and nails their strength. The smell of eggs, garlic and onions comes from sulfur compounds.

Hazards of sulfur

Pure sulfur is of low toxicity, but its dust can explode. Hydrogen sulfide (H₂S) is a deadly gas that, at high concentrations, knocks out the sense of smell before it kills. Sulfur dioxide from burning coal causes acid rain.

Cosmic origin

  • Supernovae: Forged in the cores of massive stars, then scattered when they explode.
  • White dwarfs: Produced by the thermonuclear explosion of a white dwarf (type Ia supernova).

History of sulfur

Known since prehistory, it is mentioned in the Bible and in Homer as a means of purifying homes. The Chinese used it in black powder as early as the 9th century. It was Lavoisier who, in 1777, established that it is an element and not a compound.

Did you know?

  • Io, one of Jupiter's moons, is covered in volcanoes that spew sulfur, giving it yellow and orange hues.
  • Charles Goodyear discovered vulcanization around 1839 by heating rubber mixed with sulfur.
  • The sulfur in overcooked hard-boiled eggs forms a greenish ring around the yolk (iron sulfide).

Isotopes of sulfur

Four stable isotopes, with sulfur-32 far in the lead. Radioactive sulfur-35 helped prove in 1952 that DNA, not protein, carries heredity.

  • sulfur-32: 94.99% of natural sulfur, stable
  • sulfur-33: 0.75% of natural sulfur, stable
  • sulfur-34: 4.25% of natural sulfur, stable. Shifts in its share reveal bacterial activity and the history of Earth's atmosphere.
  • sulfur-35: radioactive, half-life 87.4 days. Protein label (the Hershey–Chase experiment, 1952).
  • sulfur-36: 0.01% of natural sulfur, stable

Common compounds

Gypsum (plaster) (CaSO₄·2H₂O) · Pyrite (FeS₂) · Sulfur dioxide (SO₂) · Galena (PbS) · Cinnabar (HgS) · Sulfuric acid (H₂SO₄) · Sulfur hexafluoride (SF₆)

Related elements

Same family (nonmetals): Hydrogen (H), Carbon (C), Nitrogen (N), Oxygen (O), Phosphorus (P), Selenium (Se).

Same column (group 16): Oxygen (O), Selenium (Se), Tellurium (Te), Polonium (Po), Livermorium (Lv).