Carbon atoms are the building blocks for carbon, which is the sixth most abundant element found in the universe. A carbon atom has six electrons, four of which are in the outer shell of the atom, its valence shell.
Carbon atoms have six protons in the nucleus and six electrons orbiting around the nucleus. When neutrons are added to a carbon atom, it results in the creation of a carbon isotope. For instance, a carbon atom with only six neutrons is called Carbon-12, whereas an atom with eight neutrons is called Carbon-14. The number at the end of each isotope name represents the atomic mass number found in the periodic table. Although each isotope has varying numbers of neutrons, there is no difference to the chemical reactions of the carbon atom.
Carbon compounds come in the form of diamonds, graphite, charcoal, carbon black and fullerene. Carbon also provides the framework for all tissues of plants and animals and is an important component in proteins such as hair, meat and silk. Carbon compounds containing boron and silicon are among the hardest substances known. On a standardized scale of hardness called the Mohs scale, where diamond is 10, silicon carbide (Carborundum) is 9.15 and boron carbide is 9.32.