Carbon · element 6
Pencils, diamonds and every living cell, all built from the same four bonding electrons
Key facts
Carbon can be the softest smudge on a page or the hardest natural substance known. It can be jet black or perfectly clear, a conductor of electricity or an insulator. All of this depends on how carbon atoms arrange themselves, because carbon atoms can bond to each other in chains, rings, sheets and three-dimensional frameworks in a way no other element can match.
That flexibility is why carbon is the foundation of life. Every protein, sugar, fat and strand of DNA is built on a carbon skeleton. Roughly a fifth of a human body's mass is carbon. The element also underpins the modern world in less welcome ways, since coal, oil and natural gas are carbon-based fuels, and the carbon dioxide they release is warming the climate.
Where it is found
Carbon is not especially common in the Earth's crust, making up only around 0.02 per cent by mass, but it is everywhere that matters. It occurs in nature as two well-known pure forms, graphite and diamond. Vast amounts are locked in limestone and chalk as calcium carbonate, in fossil fuels, in soils and in the oceans as dissolved carbon dioxide.
Carbon is the fourth most abundant element in the universe by mass. It is manufactured inside stars when three helium nuclei fuse together, and it is scattered into space when those stars die. Carbon-rich dust grains, complex molecules and even tiny diamonds have been found in meteorites.
How it was discovered
Nobody discovered carbon in the usual sense. What took time was realising that these very different materials were the same element. In 1772 Antoine Lavoisier used a large lens to focus sunlight on a diamond and showed that it burned away to produce carbon dioxide, the same gas produced by burning charcoal.
In 1797 the English chemist Smithson Tennant confirmed that diamond and charcoal yielded equal amounts of the gas for equal weights, settling the matter. Lavoisier had already listed carbon as an element in 1789, taking the name from the Latin word carbo for charcoal. New pure forms have kept arriving: fullerenes in 1985, nanotubes in 1991 and graphene, a single sheet of graphite, in 2004.
What we use it for
Carbon steel, which is iron with a small amount of carbon dissolved in it, is the most widely used engineering material on Earth. Coke made from coal reduces iron ore to iron in blast furnaces. Graphite serves as pencil lead, as a lubricant, as electrodes in furnaces and as the negative electrode in most lithium-ion cells.
Diamonds cut, grind and drill as well as sparkle, and most industrial diamonds are now made synthetically. Carbon fibre, made by heating polymer threads until only carbon remains, gives aircraft, bicycles and racing cars strength at low weight. Carbon-14 dating lets archaeologists date wood, bone and cloth up to about fifty thousand years old.
Reading the numbers
Carbon has no simple melting or boiling point in the data, and that is not an omission. At normal pressure graphite does not melt at all. Heated to around 3600 degrees Celsius it turns straight into vapour, a process called sublimation. Density depends on the form: the table gives 1.82 grams per cubic centimetre, which describes amorphous carbon, while graphite is about 2.3 and diamond about 3.5, still less than half the density of iron.
The configuration [He] 2s2 2p2 gives carbon four outer electrons and four empty spaces in its outer shell. It is exactly halfway to a full shell, so it neither gives electrons away nor takes them. Instead it forms four strong covalent bonds, and it can bond to itself indefinitely. Its electronegativity of 2.55 is moderate, so carbon bonds comfortably with both hydrogen and oxygen. Carbon heads group 14 and sits in period 2, the first element with a half-filled outer shell.
Safety and the environment
Pure carbon is harmless to touch. The risks come from small particles and from its compounds. Coal dust and soot cause lung disease, and long exposure to fine particulate pollution is linked to heart and lung problems. Carbon monoxide, produced when carbon-based fuels burn with too little oxygen, is colourless, odourless and deadly, which is why homes with gas appliances need detectors.
Carbon dioxide is not toxic at everyday levels, but it is the main greenhouse gas driving climate change. Burning fossil fuels has raised its concentration in the atmosphere by about half since the industrial revolution. Understanding the carbon cycle, in which carbon moves between air, oceans, rocks and living things, is now one of the central tasks of science.
Did you know?
- Diamond and graphite are both pure carbon, yet one is the hardest natural material and the other is soft enough to write with.
- Graphene, a single layer of carbon atoms, earned Andre Geim and Konstantin Novoselov the Nobel Prize in Physics in 2010. They first peeled it from graphite with sticky tape.
- Carbon-14 has a half-life of about 5,730 years, which is what makes radiocarbon dating possible.
- Chemists know of many millions of carbon compounds, more than for all the other elements put together.
- About 18 per cent of your body mass is carbon, second only to oxygen.
- The football-shaped molecule C60, buckminsterfullerene, was discovered in 1985 and named after the architect Buckminster Fuller.
More in the non-metals
The nearest neighbours of carbon in the family, by atomic number.
See all 7 non-metals on one page, or browse all 118 elements.
Compare Carbon with another element
Each comparison has a side-by-side data table and a plain-English summary of the differences.
Frequently asked questions
Why is carbon so important for life?
Carbon atoms form four strong bonds and can link to each other in chains, rings and branches of any length. That lets them build the huge, varied molecules that living things need: proteins, DNA, sugars and fats. No other element can make such a range of stable structures.
Is diamond really made of carbon?
Yes. A diamond is pure carbon in which every atom is bonded to four neighbours in a rigid three-dimensional lattice. Heat one strongly enough in air and it burns away to carbon dioxide, exactly like charcoal.
Does carbon melt?
Not at ordinary pressure. Graphite heated to about 3600 degrees Celsius turns straight into a gas without passing through a liquid stage. Liquid carbon can only exist under very high pressure.
What is carbon dating?
Living things take in a tiny amount of radioactive carbon-14 from the air. When they die the intake stops and the carbon-14 decays at a known rate, halving every 5,730 years or so. Measuring how much is left tells scientists how long ago the organism died, back to about fifty thousand years.
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Written by Anthony. Updated September 2026. Numerical data from Periodic-Table-JSON (CC BY-SA), cross-checked against the Carbon reference article. Spotted an error? Tell us.