Carbon is a chemical element with symbol of C and the atomic number of 6. It is a nonmetallic and tetravalent atom, that has 4 electrons and it belongs to group 14 of the periodic table and there are available isotopes of carbon. While carbon-13 and carbon-12 are stable, carbon-14 is proven to be a radionuclide, and it decays with a half-life of 5,730 years, and it has been known since antiquity. The most familiar forms of carbon compounds include CO2, graphite, and diamond. It is an abundant element in the human body, after oxygen inside an human body. There are also allotropes of carbon, and diamond is one example of an allotropes, and carbon nanotubes and graphene have the highest thermal conductivity in the periodic table. All carbon allotropes are the most thermodynamically stable at standard pressure, and temperature.