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 12  Melting point −38.829°C, −37.892°F, 234.321 K 
Period Boiling point 356.619°C, 673.914°F, 629.769 K 
Block Density (g cm−3) 13.5336 
Atomic number 80  Relative atomic mass 200.592  
State at 20°C Liquid  Key isotopes 202Hg 
Electron configuration [Xe] 4f145d106s2  CAS number 7439-97-6 
ChemSpider ID 22373 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 image is of a traditional alchemical symbol for mercury. This is also an astrological symbol for the planet Mercury. The dragon or serpent in the background comes from early alchemical drawings and is often associated with the element.
A liquid, silvery metal.
Mercury has fascinated people for millennia, as a heavy liquid metal. However, because of its toxicity, many uses of mercury are being phased out or are under review.

It is now mainly used in the chemical industry as catalysts. It is also used in some electrical switches and rectifiers.

Previously its major use was in the manufacture of sodium hydroxide and chlorine by electrolysis of brine. These plants will all be phased out by 2020. It was also commonly used in batteries, fluorescent lights, felt production, thermometers and barometers. Again, these uses have been phased out.

Mercury easily forms alloys, called amalgams, with other metals such as gold, silver and tin. The ease with which it amalgamates with gold made it useful in recovering gold from its ores. Mercury amalgams were also used in dental fillings.

Mercuric sulfide (vermilion) is a high-grade, bright-red paint pigment, but is very toxic so is now only used with great care.
Biological role
Mercury has no known biological role, but is present in every living thing and widespread in the environment. Every mouthful of food we eat contains a little mercury.

Our daily intake is less than 0.01 milligrams (about 0.3 grams in a lifetime), and this we can cope with easily. However, in much higher doses it is toxic and one form of mercury – methylmercury – is particularly dangerous. It can accumulate in the flesh of fish and be eaten by people, making them ill.
Natural abundance
Mercury rarely occurs uncombined in nature, but can be found as droplets in cinnabar (mercury sulfide) ores. China and Kyrgyzstan are the main producers of mercury. The metal is obtained by heating cinnabar in a current of air and condensing the vapour.
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Cinnabar (aka vermilion, mercury sulfide, HgS), was used as a bright red pigment by the Palaeolithic painters of 30,000 years ago to decorate caves in Spain and France. Cinnabar would yield up its mercury simply on heating in a crucible, and the metal fascinated people because it was a liquid that would dissolve gold. The ancients used in on a large scale to extract alluvial gold from the sediment of rivers. The mercury dissolved the gold which could be reclaimed by distilling off the mercury.

The Almadén deposit in Spain provided Europe with its mercury. In the Americas, it was the Spanish conquerors who exploited the large deposits of cinnabar at Huancavelica in order to extract gold. In 1848 the miners of the Californian Gold Rush used mercury from the New Almaden Mines of California.

Although highly toxic, mercury had many uses, as in thermometers, but these are now strictly curtained.

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) 2.23 Covalent radius (Å) 1.32
Electron affinity (kJ mol−1) Not stable Electronegativity
(Pauling scale)
Ionisation energies
(kJ mol−1)


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 2, 1
Isotopes Isotope Atomic mass Natural abundance (%) Half life Mode of decay
  196Hg 195.966 0.15 > 2.5 x 1018 α 
  198Hg 197.967 9.97
  199Hg 198.968 16.87
  200Hg 199.968 23.1
  201Hg 200.970 13.18
  202Hg 201.971 29.86
  204Hg 203.973 6.87


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 8.6
Crustal abundance (ppm) 0.03
Recycling rate (%) <10
Substitutability Unknown
Production concentration (%) 74
Reserve distribution (%) 29
Top 3 producers
  • 1) China
  • 2) Kyrgzstan
  • 3) Chile
Top 3 reserve holders
  • 1) Mexico
  • 2) China
  • 3) Kyrgzstan
Political stability of top producer 24.1
Political stability of top reserve holder 22.6


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)
140 Young's modulus (GPa) Unknown
Shear modulus (GPa) Unknown Bulk modulus (GPa) 25
Vapour pressure  
Temperature (K)
400 600 800 1000 1200 1400 1600 1800 2000 2200 2400
Pressure (Pa)
140 - - - - - - - - - -
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Listen to Mercury Podcast
Transcript :

Chemistry in its element: mercury


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, we're exploring the link between mad hatters, mascara, the emperors of China and fishing floats; a strange combination you might say, but probably not as strange as this!

Fred Campbell

Could a man walk across a swimming pool filled with mercury? Don't ask me how the conversation had reached this point, but being surrounded by friends, who would, it is fair to say, describe themselves as science illiterate, I knew it was up to me, the token scientist around the table, to give the definitive answer. "No." I confidently said, adding rather smugly, "it is nowhere near dense enough." The next morning I was rudely awakened by my ringing mobile; I was wrong! Elemental mercury, a liquid at room temperature, is 13 times denser than water. Enough it turns out to support a man of average build and yes, if you type man sitting on mercury into Google, you'll quickly find a 1972 photograph, published in National Geographic of a man suited and booted, sat unaided, albeit a little nervously, on top of a tank of rippling mercury. I've been unequivocally proved wrong, but within a fraction of a second, this feeling had been transformed to sheer amazement. Amazement not just at the fact that mercury was so dense it could support a man, but more pressingly that the man in question was very likely giving himself a lethal dose of mercury poisoning in one fatal pose. Surely even in 1972, this kind of activity was seen as an exceptionally bad idea. This of course was not the first time that man has been lowered in by mercury.

With its Greek name, hydrargyrum, literally meaning liquid silver it's perhaps unsurprising that for the last three millennia, civilizations have been transfixed, believing mercury held wondrous physical and spiritual properties, but often those who dabbled reached an unpleasant and mercurial end. The Romans were renowned for using it in cosmetics, often disfiguring their faces in the process. The Egyptians were buried with it to illustrate their civilizations' mining prowess and the ancient Chinese drank lethal Mercury cocktails seeking eternal life and well-being. In deed, Chinese first emperor, Qin Shi Huang is said to have believed so strongly in the magical properties of Mercury that he died seeking immortality by coughing out Mercury and powdered jade, pick-me-up. His tomb yet to be fully unearthed is thought to be surrounded by great rivers of the element and guarded by the 8000 soldiers of the terracotta army.

Skipping forward to the 18th Century and for the first time, psychological illnesses were attributed to mercury exposure. The madness of many millionaires was blamed on the extensive use of mercuric nitrate in the hat industry and the phrase mad as a hatter was coined. The link almost certainly inspired Lewis Carroll to dream up the Mad Hatter, although much debate hangs over whether he is in fact displaying the symptoms of mercury poisoning. From this point on, the hazards of mercury were well documented; but despite its toxicity, it continued to find many uses in everyday applications throughout the last century. To forego reeling off a huge list of weird and wonderful uses for mercury, I would just briefly mention my personal favourite, fishing floats, used to maintain in an regular wobble on the water surface, the mercury float proves so alluring to fish that even now after its use has been globally banned, there is active research to find a replacement to do an equal job. It can still be found swirling around in dentistry, where it is used in amalgam fillings and it remains an important ingredient of many mascaras. But both these sources of mercury are currently under threat. Even the humble thermometer is gradually being phased out to be replaced by alcohol filled digital or thermistor-based instruments.

On one hand, it saddens me to think that mercury will eventually be an elemental artefact sitting hopelessly between gold and thallium in the periodic table, but on the other, it constantly reminds me of the dangers that hide behind the façade of its beautiful silver lustre. As for the man sitting on the vat of mercury, unfortunately I'm still waiting to hear back from National Geographic, for his sake though, we can only hope that he is living a long and healthy life and has not joined the long list of mercury's many victims.

Chris Smith

Chemistry World's Fred Campbell on the uses and abuses of element number 80, Quick silver, otherwise known as mercury. Here's a taste of what to look forward to next time.

Adina Payton

The first thing most people think about when this element is mentioned is barium enema or barium swallow, sickly memories often surface off the radiology clinic, where the nice nurse asked you, 'what flavour would you like, strawberry or banana'.

Chris Smith

A hard act to swallow, you could say, but thankfully a very digestible account of barium. That's coming up with Adina Payton on next week's Chemistry in its element. 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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Description :
C5e Demonstrate that dissolving, mixing and change of state are reversible.
Description :
Education in Chemistry
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The reaction between aluminium and iodine is catalysed by water. This is a spectacular demonstration as clouds of purple iodine vapour are produced.
Description :
FunKids radio, in collaboration with the RSC, has produced a set of short chemistry snippets introducing children to chemistry- the what, why and how.
Description :
This resource is designed to provide strategies for dealing with some of the misconceptions that students have in the form of ready-to-use classroom resources.
Description :
Find out more about the career of Christopher Page, a scientific associate in nuclear magnetic resonance spectroscopy. 

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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.


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