What Type of Bonds Does Carbon Form?

The Chemical Bonds Formed by Carbon

Carbon almost always forms covalent bonds, but an ionic bond is possible if the other atom has an electronegativity different from that of carbon.
Carbon almost always forms covalent bonds, but an ionic bond is possible if the other atom has an electronegativity different from that of carbon. PASIEKA / Getty Images

Carbon and its bonds are key to organic chemistry and biochemistry as well as general chemistry. Here's a look at the most common type of bond formed by carbon as well as the other chemical bonds it can also form.

Key Takeaways: Carbon Bonds

  • Carbon most often forms a covalent bond with other atoms. If the bond is with another carbon atom, it is a pure covalent bond. If it is with another atom, a polar covalent bond is formed.
  • The most common oxidation state of carbon is +4 or -4.
  • Less commonly, carbon forms ionic bonds with other atoms. This occurs when there is a large electronegativity difference between carbon and the other atom.

Carbon Forms Covalent Bonds

The most common type of bond formed by carbon is a covalent bond. In most cases, carbon shares electrons with other atoms (usual valence of 4). This is because carbon typically bonds with elements which have a similar electronegativity. Examples of covalent bonds formed by carbon include carbon-carbon, carbon-hydrogen, and carbon-oxygen bonds. Examples of compounds containing these bonds include methane, water, and carbon dioxide.

However, there are different levels of covalent bonding. Carbon can form nonpolar covalent (pure covalent) bonds when it bonds to itself, as in graphene and diamond. Carbon forms polar covalent bonds with elements that have a slightly different electronegativity. The carbon-oxygen bond is a polar covalent bond. It is still a covalent bond, but the electrons aren't shared equally between the atoms. If you are given a test question asking which type of bond carbon forms, the answer is a covalent bond.

Less Common Bonds with Carbon

However, there are less common cases in which carbon forms other types of chemical bonds. For example, the bond between calcium and carbon in calcium carbide, CaC2, is an ionic bond. Calcium and carbon have different electronegativities from each other.

Texas Carbon

While carbon typically has an oxidation state of +4 or -4, there are instances when a valence other than 4 occurs. An example is "Texas carbon," which forms 5 bonds, usually with hydrogen.