Some elements exist in several different structural forms, called allotropes. Each allotrope has different physical properties.

For more information on the Visual Elements image see the Uses and properties section below.



A vertical column in the periodic table. Members of a group typically have similar properties and electron configurations in their outer shell.

A horizontal row in the periodic table. The atomic number of each element increases by one, reading from left to right.

Elements are organised into blocks by the orbital type in which the outer electrons are found. These blocks are named for the characteristic spectra they produce: sharp (s), principal (p), diffuse (d), and fundamental (f).

Atomic number
The number of protons in an atom.

Electron configuration
The arrangements of electrons above the last (closed shell) noble gas.

Melting point
The temperature at which the solid–liquid phase change occurs.

Boiling point
The temperature at which the liquid–gas phase change occurs.

The transition of a substance directly from the solid to the gas phase without passing through a liquid phase.

Density (g cm−3)
Density is the mass of a substance that would fill 1 cm3 at room temperature.

Relative atomic mass
The mass of an atom relative to that of carbon-12. This is approximately the sum of the number of protons and neutrons in the nucleus. Where more than one isotope exists, the value given is the abundance weighted average.

Atoms of the same element with different numbers of neutrons.

CAS number
The Chemical Abstracts Service registry number is a unique identifier of a particular chemical, designed to prevent confusion arising from different languages and naming systems.

Fact box

Group 16  Melting point 115.21°C, 239.38°F, 388.36 K 
Period Boiling point 444.61°C, 832.3°F, 717.76 K 
Block Density (g cm−3) 2.07 
Atomic number 16  Relative atomic mass 32.06  
State at 20°C Solid  Key isotopes 32
Electron configuration [Ne] 3s23p4  CAS number 7704-34-9 
ChemSpider ID 4515054 ChemSpider is a free chemical structure database


Image explanation

Murray Robertson is the artist behind the images which make up Visual Elements. This is where the artist explains his interpretation of the element and the science behind the picture.


The description of the element in its natural form.

Biological role

The role of the element in humans, animals and plants.

Natural abundance

Where the element is most commonly found in nature, and how it is sourced commercially.

Uses and properties

Image explanation
The alchemical symbol for sulfur is shown against a ‘fire and brimstone’ background.
There are several allotropes of sulfur. The most common appears as yellow crystals or powder.
Sulfur is used in the vulcanisation of black rubber, as a fungicide and in black gunpowder. Most sulfur is, however, used in the production of sulfuric acid, which is perhaps the most important chemical manufactured by western civilisations. The most important of sulfuric acid’s many uses is in the manufacture of phosphoric acid, to make phosphates for fertilisers.

Mercaptans are a family of organosulfur compounds. Some are added to natural gas supplies because of their distinctive smell, so that gas leaks can be detected easily. Others are used in silver polish, and in the production of pesticides and herbicides.

Sulfites are used to bleach paper and as preservatives for many foodstuffs. Many surfactants and detergents are sulfate derivatives. Calcium sulfate (gypsum) is mined on the scale of 100 million tonnes each year for use in cement and plaster.
Biological role
Sulfur is essential to all living things. It is taken up as sulfate from the soil (or seawater) by plants and algae. It is used to make two of the essential amino acids needed to make proteins. It is also needed in some co-enzymes. The average human contains 140 grams and takes in about 1 gram a day, mainly in proteins.

Sulfur and sulfate are non-toxic. However, carbon disulfide, hydrogen sulfide and sulfur dioxide are all toxic. Hydrogen sulfide is particularly dangerous and can cause death by respiratory paralysis.

Sulfur dioxide is produced when coal and unpurified oil are burned. Sulfur dioxide in the atmosphere causes acid rain. This can cause lakes to die, partly by making toxic aluminium salts soluble, so that they are taken up by living things.
Natural abundance
Sulfur occurs naturally as the element, often in volcanic areas. This has traditionally been a major source for human use. It is also widely found in many minerals including iron pyrites, galena, gypsum and Epsom salts.

Elemental sulfur was once commercially recovered from wells by the Frasch process. This involved forcing super-heated steam into the underground deposits to melt the sulfur, so it could be pumped to the surface as a liquid.

Modern sulfur production is almost entirely from the various purification processes used to remove sulfur from natural gas, oil and tar sands. All living things contain sulfur and when fossilised (as in fossil fuels) the sulfur remains present. If unpurified fossil fuels are burnt, sulfur dioxide can enter the atmosphere, leading to acid rain.
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Sulfur is mentioned 15 times in the Bible, and was best known for destroying Sodom and Gomorrah. It was also known to the ancient Greeks, and burnt as a fumigant. Sulfur was mined near Mount Etna in Sicily and used for bleaching cloth and preserving wine, both of which involved burning it to form sulfur dioxide, and allowing this to be absorbed by wet clothes or the grape juice. For centuries, sulfur along with mercury and salt, was believed to be a component of all metals and formed the basis of alchemy whereby one metal could be transmuted into another.

Antoine Lavoisier thought that sulfur was an element, but in 1808 Humphry Davy said it contained hydrogen. However, his sample was impure and when Louis-Josef Gay-Lussac and Louis-Jacques Thénard proved it to be an element the following year, Davy eventually agreed.

Atomic radius, non-bonded
Half of the distance between two unbonded atoms of the same element when the electrostatic forces are balanced. These values were determined using several different methods.

Covalent radius
Half of the distance between two atoms within a single covalent bond. Values are given for typical oxidation number and coordination.

Electron affinity
The energy released when an electron is added to the neutral atom and a negative ion is formed.

Electronegativity (Pauling scale)
The tendency of an atom to attract electrons towards itself, expressed on a relative scale.

First ionisation energy
The minimum energy required to remove an electron from a neutral atom in its ground state.

Atomic data

Atomic radius, non-bonded (Å) 1.80 Covalent radius (Å) 1.04
Electron affinity (kJ mol−1) 200.41 Electronegativity
(Pauling scale)
Ionisation energies
(kJ mol−1)

Bond enthalpy (kJ mol−1)
A measure of how much energy is needed to break all of the bonds of the same type in one mole of gaseous molecules.

Bond enthalpies

Covalent bond Enthalpy (kJ mol−1) Found in
S–S 226 S8
S=S 351 S2
H–S 347 H2S
O=S 435 SO3


Common oxidation states

The oxidation state of an atom is a measure of the degree of oxidation of an atom. It is defined as being the charge that an atom would have if all bonds were ionic. Uncombined elements have an oxidation state of 0. The sum of the oxidation states within a compound or ion must equal the overall charge.


Atoms of the same element with different numbers of neutrons.

Key for isotopes

Half life
  y years
  d days
  h hours
  m minutes
  s seconds
Mode of decay
  α alpha particle emission
  β negative beta (electron) emission
  β+ positron emission
  EC orbital electron capture
  sf spontaneous fission
  ββ double beta emission
  ECEC double orbital electron capture

Oxidation states and isotopes

Common oxidation states 6, 4, 2, -2
Isotopes Isotope Atomic mass Natural abundance (%) Half life Mode of decay
  32S 31.972 94.99
  33S 32.971 0.75
  34S 33.968 4.25
  36S 35.967 0.01


Data for this section been provided by the British Geological Survey.

Relative supply risk

An integrated supply risk index from 1 (very low risk) to 10 (very high risk). This is calculated by combining the scores for crustal abundance, reserve distribution, production concentration, substitutability, recycling rate and political stability scores.

Crustal abundance (ppm)

The number of atoms of the element per 1 million atoms of the Earth’s crust.

Recycling rate

The percentage of a commodity which is recycled. A higher recycling rate may reduce risk to supply.


The availability of suitable substitutes for a given commodity.
High = substitution not possible or very difficult.
Medium = substitution is possible but there may be an economic and/or performance impact
Low = substitution is possible with little or no economic and/or performance impact

Production concentration

The percentage of an element produced in the top producing country. The higher the value, the larger risk there is to supply.

Reserve distribution

The percentage of the world reserves located in the country with the largest reserves. The higher the value, the larger risk there is to supply.

Political stability of top producer

A percentile rank for the political stability of the top producing country, derived from World Bank governance indicators.

Political stability of top reserve holder

A percentile rank for the political stability of the country with the largest reserves, derived from World Bank governance indicators.

Supply risk

Relative supply risk 3.5
Crustal abundance (ppm) 404
Recycling rate (%) Unknown
Substitutability Unknown
Production concentration (%) 17.4
Reserve distribution (%) Unknown
Top 3 producers
  • 1) China
  • 2) USA
  • 3) Canada
Top 3 reserve holders
  • Unknown
Political stability of top producer 24.1
Political stability of top reserve holder Unknown


Specific heat capacity (J kg−1 K−1)

Specific heat capacity is the amount of energy needed to change the temperature of a kilogram of a substance by 1 K.

Young's modulus

A measure of the stiffness of a substance. It provides a measure of how difficult it is to extend a material, with a value given by the ratio of tensile strength to tensile strain.

Shear modulus

A measure of how difficult it is to deform a material. It is given by the ratio of the shear stress to the shear strain.

Bulk modulus

A measure of how difficult it is to compress a substance. It is given by the ratio of the pressure on a body to the fractional decrease in volume.

Vapour pressure

A measure of the propensity of a substance to evaporate. It is defined as the equilibrium pressure exerted by the gas produced above a substance in a closed system.

Pressure and temperature data – advanced

Specific heat capacity
(J kg−1 K−1)
708 Young's modulus (GPa) Unknown
Shear modulus (GPa) Unknown Bulk modulus (GPa) 7.7
Vapour pressure  
Temperature (K)
400 600 800 1000 1200 1400 1600 1800 2000 2200 2400
Pressure (Pa)
- - - - - - - - - - -
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Listen to Sulfur Podcast
Transcript :

Chemistry in its element: sulfur


You're listening to Chemistry in its element brought to you by Chemistry World, the magazine of the Royal Society of Chemistry.

(End promo)

Chris Smith

Hello, this week stinky sediments, skunks and the smell of hell. Well they all begin with the letter S, and so does this week's element. Here's Steve Mylon.

Steve Mylon

"How did it smell?" That was the only question I needed to ask a geologist colleague of mine about the sediment she was trying to understand. The smell of the sediment tells a great deal about the underlying chemistry. Thick black anoxic sediments can be accompanied by a putrid smell which is unique to reduced sulfur.

Maybe this is why sulfur has such a bad reputation. My son wouldn't eat eggs for 6 months when he got a smell of his first rotten one. In the bible it seems that whenever something bad happens or is about to happen burning sulfur is in the picture:

For example,

In Genesis we hear, "the lord rained down burning sulfur on Sodom and Gomorrah"

And in Revelation we read that the sinners will find their place in a fiery lake of burning sulfur."

The odd thing is that in both cases we shouldn't expect anything smelly to be produced. When sulfur burns in air, it generally forms sulfur dioxide or sulfur trioxide, the latter of which lacks any smell [amended from the podcast audio file, which states that sulfur dioxide does not smell]. These compounds can further oxidize and rain out as sulfuric or sulfurous acid. This is the mechanism for acid rain which has reeked havoc on the forests of the northeastern United States as sulfur rich coals are burned to generate electricity in midwestern states and carried east by prevailing winds where sulfuric acid is rained out causing all sorts of ecological problems.

Additionally, the combination of burning coal and fog creates smog in many industrial cities causing respiratory problems among the locals. Here too, sulfur dioxide and sulfuric acid are implicated as the culprits. But again, there is no smell associated with this form of sulfur.

So if hell or the devil is said have the 'smell of sulfur', maybe that's not so bad.

But reduce sulfur by giving it a couple of electrons, and its smell is unmistakable. The requirement of sulfur reduction to sulfide has clearly been lost in translation .

Hell that smells like hydrogen sulfide or any number of organic-sulfur compound will not be a nice place at all. The organic sulfide compounds known as thiols or mercaptans smell so bad, that they are commonly added to odorless natural gas in very small quantities in order to serve as a 'smell alarm' should there be leak in a natural gas line. Skunks take advantage of the foul smell of butyl seleno-mercaptan as a means of defending themselves against their enemies. And for me, personally, the worst chemistry of all occurs when reduced sulfur imparts a bad (skunky) taste in bottles of wine or beer. -bound to ruin a nice night out on the town or an afternoon at the local pub.

So, where does the "smell of hell" come from in anoxic sediments. Interestingly, some bacteria have evolved to make use of oxidized sulfur , sulfate, as an electron acceptor during respiration. In a similar manner to the way humans reduce elemental oxygen to water, these bacteria reduce sulfate to hydrogen sulfide- They clearly don't mind the smell.

Smell is not the only interesting chemistry that accompanies reduced sulfur. The deep black associated with anoxic sediments results from the low solubility of most metal sulfides. Sulfate reduction to sulfide generally accompanies the precipitation of pyrite (iron sulfide), cinnabar (mercury sulfide), galena (lead sulfide) and many more minerals. These metal sulfides have become an important industrial source for many of these important metals.

Industry is one place you are almost certain to find sulfur or more importantly sulfuric acid which is used in processes ranging from fertilizer production to oil refining. In fact sulfuric acid ranks as the most highly produced chemical in the industrialized world. Imagine that, the element with such a hellish reputation has become one of the most important.

And some even suggest that sulfur could save the planet. The biogenic compound dimethylsulfide (DMS) is produced from the cleavage of dimethylsufonoprioponate, an osmotic regulatory compound produced by plankton in the ocean. The volatility and low solubility of DMS results in some 20 Tg (10^12) of sulfur emitted to the atmosphere annually. DMS is oxidized to SO2 and finally to sulfuric acid particles which can act as cloud condensation nuclei forming clouds which have a net cooling effect to the planet.

Imagine warmer temperatures followed by greater biological activity resulting in more DMS to the atmosphere. The resulting cloud formation might work to cool a warming planet. It's almost like the plankton are opening an umbrella made up-in part- of sulfur. From a symbol of damnation to savior...what a turn around!!.

Chris Smith

Steve Mylon sniffing out the stinky story of Sulfur. Thankfully next week's element is a lot less odiforous.

John Emsley

The story of its discovery started when Rayleigh found that the nitrogen extracted from the air had a higher density than that made by decomposing ammonia. The difference was small but real. Ramsay wrote to Rayleigh suggesting that he should look for a heavier gas in the nitrogen got from air, while Rayleigh should look for a lighter gas in that from ammonia. Ramsay removed all the nitrogen from his sample by repeatedly passing it over heated magnesium. He was left with one percent which would not react and found it was denser than nitrogen. Its atomic spectrum showed new red and green lines, confirming it a new element.

Chris Smith

And that new element was Argon nicknamed the lazy element because originally scientists thought that it wouldn't react with anything. Now we know that's not true and John Emsley will be here to unlock Argon secrets on next week's Chemistry in its Element, I hope you can join us. I'm Chris Smith, thank you for listening and goodbye.


Chemistry in its element is brought to you by the Royal Society of Chemistry and produced by There's more information and other episodes of Chemistry in its element on our website at

(End promo)
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Visual Elements images and videos
© Murray Robertson 1998-2017.



W. M. Haynes, ed., CRC Handbook of Chemistry and Physics, CRC Press/Taylor and Francis, Boca Raton, FL, 95th Edition, Internet Version 2015, accessed December 2014.
Tables of Physical & Chemical Constants, Kaye & Laby Online, 16th edition, 1995. Version 1.0 (2005), accessed December 2014.
J. S. Coursey, D. J. Schwab, J. J. Tsai, and R. A. Dragoset, Atomic Weights and Isotopic Compositions (version 4.1), 2015, National Institute of Standards and Technology, Gaithersburg, MD, accessed November 2016.
T. L. Cottrell, The Strengths of Chemical Bonds, Butterworth, London, 1954.


Uses and properties

John Emsley, Nature’s Building Blocks: An A-Z Guide to the Elements, Oxford University Press, New York, 2nd Edition, 2011.
Thomas Jefferson National Accelerator Facility - Office of Science Education, It’s Elemental - The Periodic Table of Elements, accessed December 2014.
Periodic Table of Videos, accessed December 2014.


Supply risk data

Derived in part from material provided by the British Geological Survey © NERC.


History text

Elements 1-112, 114, 116 and 117 © John Emsley 2012. Elements 113, 115, 117 and 118 © Royal Society of Chemistry 2017.



Produced by The Naked Scientists.


Periodic Table of Videos

Created by video journalist Brady Haran working with chemists at The University of Nottingham.