What is the atomic number of carbon?

The atomic number of carbon is 6. Every carbon atom has six protons in its nucleus, and that proton count is what defines the element carbon.

A neutral carbon atom also has six electrons, arranged in two electron shells: two in the first shell and four in the second. Carbon's four outer-shell electrons allow it to form stable bonds with many elements, including other carbon atoms. This bonding flexibility makes carbon the structural basis of organic chemistry and of all known biological molecules.

The number 12 is a common distractor because carbon-12 is the most abundant naturally occurring isotope of carbon. The 12 refers to its mass number—the six protons plus six neutrons—not its atomic number. Carbon also occurs naturally as carbon-13 and radioactive carbon-14.

Carbon occupies position 6 on the periodic table, between boron and nitrogen. Its symbol is C, and it is a nonmetal found in forms ranging from diamond and graphite to carbon dioxide, fuels, sugars, proteins, and DNA.