Carbon
Carbon is the sixth element on the periodic table, having six protons in its nucleus. The most common number of neutrons in its nucleus is also six and the Carbon-12 isotope is the basis for atomic weights, with the mass of the proton being defined as 1/12 of the mass of the Carbon nucleus.
The next most common isotope is Carbon-14 with 8 neutrons in the nucleus. C-14 is the isotope famous for its use in carbon radiometric dating techniques.
Carbon has two elemental forms, the more common of which is black graphite. Less common but probably far more well known is diamond.
Carbon can form up to four covalent bonds with other elements. This property makes it highly suited for building long chains of atoms together. It is these chains that form the building blocks of life, primarily carbohydrates, lipids, proteins, nucleic acids and so forth.
Atomic mass: 12.0107 g/mol
Chemical symbol: C