Periodic Table > Carbon
 

Glossary


Allotropes
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.

 

Glossary


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


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


Block
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.


Sublimation
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.


Isotopes
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 14  Melting point Sublimes at 3825°C, 6917°F, 4098 K 
Period Boiling point Sublimes at 3825°C, 6917°F, 4098 K 
Block Density (g cm−3) 3.513 (diamond); 2.2 (graphite) 
Atomic number Relative atomic mass 12.011  
State at 20°C Solid  Key isotopes 12C, 13C, 14
Electron configuration [He] 2s22p2  CAS number 7440-44-0 
ChemSpider ID 4575370 ChemSpider is a free chemical structure database
 

Glossary


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.


Appearance

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 three crowns represent the three major forms of the element in nature and carbon’s status as ‘King of the Elements’ in the periodic table.
Appearance
There are a number of pure forms of this element including graphite, diamond, fullerenes and graphene.

Diamond is a colourless, transparent, crystalline solid and the hardest known material. Graphite is black and shiny but soft. The nano-forms, fullerenes and graphene, appear as black or dark brown, soot-like powders.
Uses
Carbon is unique among the elements in its ability to form strongly bonded chains, sealed off by hydrogen atoms. These hydrocarbons, extracted naturally as fossil fuels (coal, oil and natural gas), are mostly used as fuels. A small but important fraction is used as a feedstock for the petrochemical industries producing polymers, fibres, paints, solvents and plastics etc.

Impure carbon in the form of charcoal (from wood) and coke (from coal) is used in metal smelting. It is particularly important in the iron and steel industries.

Graphite is used in pencils, to make brushes in electric motors and in furnace linings. Activated charcoal is used for purification and filtration. It is found in respirators and kitchen extractor hoods.

Carbon fibre is finding many uses as a very strong, yet lightweight, material. It is currently used in tennis rackets, skis, fishing rods, rockets and aeroplanes.

Industrial diamonds are used for cutting rocks and drilling. Diamond films are used to protect surfaces such as razor blades.

The more recent discovery of carbon nanotubes, other fullerenes and atom-thin sheets of graphene has revolutionised hardware developments in the electronics industry and in nanotechnology generally.

150 years ago the natural concentration of carbon dioxide in the Earth’s atmosphere was 280 ppm. In 2013, as a result of combusting fossil fuels with oxygen, there was 390 ppm. Atmospheric carbon dioxide allows visible light in but prevents some infrared escaping (the natural greenhouse effect). This keeps the Earth warm enough to sustain life. However, an enhanced greenhouse effect is underway, due to a human-induced rise in atmospheric carbon dioxide. This is affecting living things as our climate changes.
Biological role
Carbon is essential to life. This is because it is able to form a huge variety of chains of different lengths. It was once thought that the carbon-based molecules of life could only be obtained from living things. They were thought to contain a ‘spark of life’. However, in 1828, urea was synthesised from inorganic reagents and the branches of organic and inorganic chemistry were united.

Living things get almost all their carbon from carbon dioxide, either from the atmosphere or dissolved in water. Photosynthesis by green plants and photosynthetic plankton uses energy from the sun to split water into oxygen and hydrogen. The oxygen is released to the atmosphere, fresh water and seas, and the hydrogen joins with carbon dioxide to produce carbohydrates.

Some of the carbohydrates are used, along with nitrogen, phosphorus and other elements, to form the other monomer molecules of life. These include bases and sugars for RNA and DNA, and amino acids for proteins.

Living things that do not photosynthesise have to rely on consuming other living things for their source of carbon molecules. Their digestive systems break carbohydrates into monomers that they can use to build their own cellular structures. Respiration provides the energy needed for these reactions. In respiration oxygen rejoins carbohydrates, to form carbon dioxide and water again. The energy released in this reaction is made available for the cells.
Natural abundance
Carbon is found in the sun and other stars, formed from the debris of a previous supernova. It is built up by nuclear fusion in bigger stars.

It is present in the atmospheres of many planets, usually as carbon dioxide. On Earth, the concentration of carbon dioxide in the atmosphere is currently 390 ppm and rising.

Graphite is found naturally in many locations. Diamond is found in the form of microscopic crystals in some meteorites. Natural diamonds are found in the mineral kimberlite, sources of which are in Russia, Botswana, DR Congo, Canada and South Africa.

In combination, carbon is found in all living things. It is also found in fossilised remains in the form of hydrocarbons (natural gas, crude oil, oil shales, coal etc) and carbonates (chalk, limestone, dolomite etc).
 
Glossary

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) 1.70 Covalent radius (Å) 0.75
Electron affinity (kJ mol−1) 121.776 Electronegativity
(Pauling scale)
2.55
Ionisation energies
(kJ mol−1)
 
1st
1086.454
2nd
2352.631
3rd
4620.471
4th
6222.716
5th
37830.648
6th
47277.174
7th
-
8th
-
 
Glossary

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
C–C 345.6 general
C=C 610 general
C≡C 835.1 general
C–N 304.6 general
C=N 615 general
C≡N 889.5 general
C–F 485 CF4
C–Si 301 (CH3)4Si
C–Cl 339 general
C–Cl 327.2 CCl4
C–I 218 general
C–I 213 CH3I
C–Br 285 general
C–H 413 general
C–H 415.5 CH4
C–O 357.7 general
C=O 803 CO2
C=O 695 HCHO
C=O 736 aldehydes
C=O 749 ketones
C–O 335.6 CH3OH
 

Glossary

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.


Substitutability

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

 
Coal
Relative supply risk 4.5
Crustal abundance (ppm) 200
Recycling rate (%) Unknown
Substitutability Unknown
Production concentration (%) 46
Reserve distribution (%) 28
Top 3 producers
  • 1) China
  • 2) USA
  • 3) India
Top 3 reserve holders
  • 1) USA
  • 2) Russia
  • 3) China
Political stability of top producer 24.1
Political stability of top reserve holder 56.6
Diamond
Relative supply risk 6.2
Crustal abundance (ppm) 200
Recycling rate (%) Unknown
Substitutability Unknown
Production concentration (%) 27
Reserve distribution (%) 25
Top 3 producers
  • 1) Russia
  • 2) Botswana
  • 3) DRC
Top 3 reserve holders
  • 1) DRC
  • 2) Botswana
  • 3) Australia
Political stability of top producer 18.4
Political stability of top reserve holder 2.8
Graphite
Relative supply risk 8.1
Crustal abundance (ppm) 200
Recycling rate (%) Unknown
Substitutability Medium
Production concentration (%) 84
Reserve distribution (%) 71
Top 3 producers
  • 1) China
  • 2) India
  • 3) Brazil
Top 3 reserve holders
  • 1) China
  • 2) India
  • 3) Mexico
Political stability of top producer 24.1
Political stability of top reserve holder 24.1
 

Glossary


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.


Isotopes

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 4, 3, 2, 1, 0, -1, - 2, -3, -4
Isotopes Isotope Atomic mass Natural abundance (%) Half life Mode of decay
  12C 12.000 98.93
  13C 13.003 1.07
  14C 14.003 - 5715 y  β- 
 

Glossary


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)
709 (graphite) Young's modulus (GPa) Unknown
Shear modulus (GPa) Unknown Bulk modulus (GPa) 542 (diamond);33 (graphite)
Vapour pressure  
Temperature (K)
400 600 800 1000 1200 1400 1600 1800 2000 2200 2400
Pressure (Pa)
- - - - - - - - - - -
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History

Carbon occurs naturally as anthracite (a type of coal), graphite, and diamond. More readily available historically was soot or charcoal. Ultimately these various materials were recognised as forms of the same element. Not surprisingly, diamond posed the greatest difficulty of identification. Naturalist Giuseppe Averani and medic Cipriano Targioni of Florence were the first to discover that diamonds could be destroyed by heating. In 1694 they focussed sunlight on to a diamond using a large magnifying glass and the gem eventually disappeared. Pierre-Joseph Macquer and Godefroy de Villetaneuse repeated the experiment in 1771. Then, in 1796, the English chemist Smithson Tennant finally proved that diamond was just a form of carbon by showing that as it burned it formed only CO2.
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Podcasts

Listen to Carbon Podcast
Transcript :

Chemistry in its element: carbon


(Promo)

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 to the element that unites weddings, wars, conflicts and cremations and to explain how, here's Katherine Holt.

Katherine Holt

Any chemist could talk for days about carbon. It is after all an everyday, run-of-the-mill, found-in-pretty-much-everything, ubiquitous element for us carbon-based life forms. An entire branch of chemistry is devoted to its reactions.

In its elemental form it throws up some surprises in the contrasting and fascinating forms of its allotropes. It seems that every few years a new form of carbon comes into fashion - A few years ago carbon nanotubes were the new black (or should I say 'the new bucky-ball') - but graphene is oh-so-now!

But today I'm going to talk about the most glamorous form that carbon can take - diamond. For millennia diamond has been associated with wealth and riches, as it can be cut to form gemstones of high clarity, brilliance and permanence. Diamonds truly are forever! Unfortunately, diamond also has a dark side - the greed that diamond induces leads to the trade of so-called 'conflict diamonds' that support and fund civil wars.

Mans desire for diamond has led alchemists and chemists over many centuries to attempt to synthesise the material. After many fraudulous early claims diamond was finally synthesised artificially in the 1950s. Scientists took their inspiration from nature by noting the conditions under which diamond is formed naturally, deep under the earth's crust. They therefore used high temperatures (over 3000oC) and high pressures (>130 atms) to turn graphite into carbon. This was an impressive feat, but the extreme conditions required made it prohibitively expensive as a commercial process. Since then the process has been refined and the use of metal catalysts means that lower temperatures and pressures are required. Crystals of a few micron diameter can be formed in a few minutes, but a 2-carat gem quality crystal may takes several weeks.

These techniques mean its now possible to artificially synthesise gemstone quality diamonds which, without the help of specialist equipment, cannot be distinguished from natural diamond. It goes without saying that this could cause headaches among the companies that trade in natural diamond! It is possible to turn any carbon based material into a diamond - including hair and even cremating remains! Yes - you can turn your dearly departed pet into a diamond to keep forever if you want to! Artificial diamonds are chemically and physical identical to the natural stones and come without the ethical baggage. However, psychologically their remains a barrier - if he really loves you he'd buy you real diamond - wouldn't he?

From the perspective of a chemist, materials scientist or engineer we soon run out of superlatives while describing the amazing physical, electronic and chemical properties of diamond. It is the hardest material known to man and more or less inert - able to withstand the strongest and most corrosive of acids. It has the highest thermal conductivity of any material, so is excellent at dissipating heat. That is why diamonds are always cold to the touch. Having a wide band gap, it is the text book example of an insulating material and for the same reason has amazing transparency and optical properties over the widest range of wavelengths of any solid material.

You can see then why diamond is exciting to scientists. Its hardness and inert nature suggest applications as protective coatings against abrasion, chemical corrosion and radiation damage. Its high thermal conductivity and electrical insulation cry out for uses in high powered electronics. Its optical properties are ideal for windows and lenses and its biocompatibility could be exploited in coatings for implants.

These properties have been known for centuries - so why then is the use of diamond not more widespread? The reason is that natural diamond and diamonds formed by high pressure high temperature synthesis are of limited size - usually a few millimeters at most, and can only be cut and shaped along specific crystal faces. This prevents the use of diamond in most of the suggested applications.

However, about 20 years ago scientists discovered a new way to synthesise diamond this time under low pressure, high temperature conditions, using chemical vapour deposition. If one were to consider the thermodynamic stability of carbon, we would find that at room temperature and pressure the most stable form of carbon is actually graphite, not diamond. Strictly speaking, from a purely energetic or thermodynamic point of view, diamond should spontaneously turn into graphite under ambient conditions! Clearly this doesn't happen and that is because the energy required to break the strong bonds in diamond and rearrange them to form graphite requires a large input of energy and so the whole process is so slow that on the scale of millennia the reaction does not take place.

It is this metastability of diamond that is exploited in chemical vapour deposition. A gas mixture of 99 % hydrogen and 1 % of methane is used and some activation source like a hot filament employed to produce highly reactive hydrogen and methyl radicals. The carbon-based molecules then deposit on a surface to form a coating or thin film of diamond. Actually both graphite and diamond are initially formed, but under these highly reactive conditions, the graphitic deposits are etched off the surface, leaving only the diamond. The films are polycrystalline, consisting of crystallites in the micron size range so lack the clarity and brilliance of gemstone diamond. While they may not be as pretty, these diamond films can be deposited on a range of surfaces of different size and shapes and so hugely increase the potential applications of diamond. Challenges still remain to understand the complex chemistry of the intercrystalline boundaries and surface chemistry of the films and to learn how best to exploit them. This material will be keeping chemists, materials scientists, physicists and engineers busy for many years to come. However, at present we can all agree that there is more to diamond than just a pretty face!

Chris Smith

Katherine Holt extolling the virtues of the jewel in carbon's crown. Next week we're heading to the top of group one to hear the story of the metal that revolutionised the treatment of manic depression.

Matt Wilkinson

Its calming effect on the brain was first noted in 1949, by an Australian doctor, John Cade, of the Victoria Department of Mental Hygiene. He had injected guinea pigs with a 0.5% solution of lithium carbonate, and to his surprise these normally highly-strung animals became docile. Cade then gave his most mentally disturbed patient an injection of the same solution. The man responded so well that within days he was transferred to a normal hospital ward and was soon back at work.

Chris Smith

And it's still used today although despite 50 years of medical progress we still don't know how it works. That was Matt Wilkinson who will be here with the story of Lithium on next week's Chemistry in its Element, I do hope you can join us. I'm Chris Smith, thank you for listening and goodbye.

(Promo)

Chemistry in its element is brought to you by the Royal Society of Chemistry and produced by thenakedscientists.com. There's more information and other episodes of Chemistry in its element on our website at chemistryworld.org/elements.

(End promo)
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Resources

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In this experiment you will remove odjectionable tastes and odours from drinking water using carbon. Carbon that has undergone special treatment (sometimes called activated charcoal) has useful absorp...
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The discovery of buckminsterfullerene, the third allotrope of carbon.
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Two unnamed black solids are known to be either copper(II) oxide or carbon.  Devise three or more methods of labelling them correctly using chemicals and apparatus in the laboratory, test each method ...
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References

 
Visual Elements images and videos
© Murray Robertson 2011.

 

Data

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 3.0), 2010, National Institute of Standards and Technology, Gaithersburg, MD, accessed December 2014.
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

© John Emsley 2012.

 

Podcasts

Produced by The Naked Scientists.

 

Periodic Table of Videos

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