Sulfur · element 16
The yellow element behind rotten-egg smells, match heads and almost every acid factory on Earth
Key facts
Sulfur is one of the few elements you can pick up straight out of the ground and recognise. Around volcanic vents it forms bright yellow crusts, and a lump of it burns with a blue flame and a sharp, choking smell. People have known it for thousands of years, long before anyone had the idea of a chemical element.
Today it is far less visible but far more important. Most of the sulfur produced each year is turned into sulfuric acid, which is made in such huge quantities that a country's output of it is sometimes used as a rough measure of how much manufacturing it does.
Where it is found
Pure sulfur occurs naturally in volcanic regions and in salt domes, where bacteria and hot water have stripped it out of other minerals over long periods. Sicily was the world's main supplier for much of the nineteenth century. In the twentieth century the Frasch process, which pumps superheated water underground to melt the sulfur and force it to the surface, opened up large deposits along the Gulf of Mexico.
Most sulfur today does not come from mines at all. It is removed from crude oil and natural gas at refineries, because sulfur compounds would otherwise poison catalysts and produce acid rain when the fuel is burned. This recovered sulfur now supplies the bulk of the world market. Sulfur is also locked into minerals such as pyrite (iron sulfide), gypsum (calcium sulfate) and galena (lead sulfide). In your own body it is part of two amino acids that help hold proteins in shape.
How it was discovered
Nobody discovered sulfur in the modern sense. It appears in ancient Chinese, Indian and Egyptian records, and it is the brimstone of the Bible. Chinese alchemists mixed it with charcoal and saltpetre to make early gunpowder. For centuries it was treated as a principle of combustibility rather than a substance in its own right. Antoine Lavoisier listed it as an element in 1777, and its atomic weight was pinned down during the nineteenth century as chemistry became a quantitative science.
What we use it for
Sulfuric acid is the giant. It is used to make phosphate fertilisers, to process metal ores, to refine petroleum, to make detergents and pigments, and as the electrolyte in car batteries. Sulfur itself vulcanises rubber, a process discovered by Charles Goodyear in which sulfur atoms form bridges between long rubber molecules and turn a soft, sticky material into something tough enough for tyres.
Sulfur compounds also give us matches, fungicides for vineyards, and the sulfites that preserve dried fruit and wine. Sulfur dioxide bleaches paper pulp. In medicine, the sulfonamide drugs were the first widely used antibacterials, and many modern medicines still carry sulfur atoms in their structures.
Reading the numbers
Sulfur melts at about 115 °C, roughly the temperature of a domestic oven on a low setting, and boils at about 445 °C. That low melting point is what makes the Frasch process possible. Its density is 2.07 g/cm³, about twice that of water but only a quarter of iron, so a lump feels light for a mineral. The electron configuration [Ne] 3s2 3p4 shows six outer electrons, two short of a full shell. Like oxygen directly above it in group 16, sulfur tends to gain two electrons or form two bonds, giving sulfides and the S2- ion. Unlike oxygen, its larger atoms can link into chains and rings, which is why ordinary solid sulfur is built from crown-shaped rings of eight atoms and why it has so many different solid forms. Its electronegativity of 2.58 is high for period 3 but well below chlorine next door, so its bonds to metals are less ionic than chlorine's.
Safety and the environment
Pure sulfur is not very toxic and is used in skin creams. The problems come from its compounds. Burning sulfur produces sulfur dioxide, which irritates the lungs and reacts in the air to form sulfuric acid, the main cause of the acid rain that damaged forests and lakes in Europe and North America in the twentieth century. Regulations forcing power stations and ships to strip sulfur from fuel have sharply reduced this. Hydrogen sulfide, the rotten-egg gas from sewers and some volcanoes, is dangerously toxic at high concentrations, and worse, it deadens the sense of smell so a victim may stop noticing it.
Did you know?
- Sulfur has more solid forms, or allotropes, than any other element; the familiar yellow crystals are made of rings of eight atoms.
- When molten sulfur is heated further it becomes darker and thicker instead of thinner, because the rings break open and tangle into long chains.
- Sulfur burns with a blue flame, which is why brimstone became so closely linked with fire in old writings.
- Jupiter's moon Io is painted yellow, orange and white largely by sulfur and sulfur dioxide frost from its hundreds of active volcanoes.
- Garlic, onions, skunk spray and rotten eggs all get their smell from sulfur compounds, yet pure sulfur itself has almost no odour.
- IUPAC adopted the spelling sulfur in 1990, though sulfur remains common in British writing.
More in the non-metals
Column-mates come first, since elements in one column have outer electrons arranged in a similar way and tend to behave alike; the rest are the nearest neighbours in the family.
See all 7 non-metals on one page, or browse all 118 elements.
Compare Sulfur with another element
Each comparison has a side-by-side data table and a plain-English summary of the differences.
Frequently asked questions
Why does sulfur smell of rotten eggs?
It does not. Pure sulfur is almost odourless. The rotten-egg smell comes from hydrogen sulfide, a gas made when sulfur compounds decay without oxygen, and the sharp smell of a struck match is sulfur dioxide.
Is sulfur a metal?
No. Sulfur is a non-metal in group 16, below oxygen. It is a brittle yellow solid that does not conduct electricity and gains electrons in reactions rather than losing them.
Why is sulfur yellow?
The eight-atom rings in solid sulfur absorb violet and blue light and reflect the rest, which our eyes see as yellow. When sulfur is melted or heated the rings break and the colour shifts to orange, red and eventually almost black.
Is sulfur dangerous to touch?
Solid sulfur is safe to handle and is used in some skin treatments. The hazards are its compounds, especially sulfur dioxide from burning it and hydrogen sulfide, both of which harm the lungs.
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Written by Anthony. Updated September 2026. Numerical data from Periodic-Table-JSON (CC BY-SA), cross-checked against the Sulfur reference article. Spotted an error? Tell us.