Carbon

Carbon is the chemical element with symbol C and atomic number 6. It has an atomic mass of

 12.0107, which means that each carbon atom has a mass of about 12 atomic mass units. Carbon is a

 nonmetal, meaning that it does not react with water or dissolve in acids.[1] The air we breathe out

 contains about 4% carbon dioxide by weight. The United States Environmental Protection Agency

 estimates that human activity including the burning of fossil fuels, agriculture, and deforestation

 has resulted in over 550 billion metric tons of carbon being released as carbon dioxide into the

 atmosphere since the mid-1850s.[2] Carbon is a necessary part of life on Earth. It exists in all living

things. The average adult human body contains about 18 to 20 pounds (8 to 9 kilograms) of carbon.

[1] Carbon is also present in all organic compounds in trace amounts (less than 0.04%).