Which element has atomic number 6?
Quick answer
Carbon (symbol C) is the element with atomic number 6, meaning every carbon atom has six protons in its nucleus. Carbon is the basis of all known life and forms more compounds than almost any other element. It comes in very different forms, from soft graphite to diamond, the hardest natural material.
Key facts
- Symbol
- C
- Atomic number
- 6
- Group
- Group 14 (nonmetal)
- Rank in the universe
- About the 4th most abundant element
What “atomic number” means
An element’s atomic number is the number of protons in each atom’s nucleus, and it defines the element. Change the number of protons and you get a different element. Most carbon atoms also have six neutrons; see who discovered the neutron.
Many forms of carbon
Pure carbon can arrange its atoms in different ways, called allotropes:
| Form | Structure | Properties |
|---|---|---|
| Diamond | 3D network of strong bonds | Hardest natural substance; see the hardest mineral |
| Graphite | Stacked flat sheets | Soft and slippery; used in pencils |
| Graphene | A single sheet one atom thick | Extremely strong and conductive; isolated in 2004 |
| Fullerenes | Hollow balls and tubes | “Buckyballs” shaped like soccer balls |
Why life is built on carbon
Carbon can form four bonds at once, linking with other carbon atoms into long chains and rings. This lets it build the huge, complex molecules life needs: DNA, proteins, sugars and fats; see what amino acids are. The chemistry of carbon compounds is called organic chemistry.
Carbon dating
A rare form, carbon-14, is radioactive and decays at a steady rate, with a half-life of about 5,730 years. Living things take in carbon-14 until they die. By measuring how much is left, scientists can date bones, wood and cloth up to about 50,000 years old. Willard Libby developed the method in the late 1940s.
Carbon in the air
Carbon dioxide (CO₂) makes up only about 0.04% of the air, but it traps heat and plays a key role in Earth’s climate. Plants absorb it to make food; animals breathe it out. It’s also the gas in fizzy drinks; see what makes soda fizzy.
Where it ranks
Carbon is forged inside stars and is roughly the fourth most abundant element in the universe; see the most abundant element in the universe.
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