Answer:
I am carbon atom denoted by a symbol C and my atomic number is 6. I am the member of group 14 in the periodic table. I am tetravalent having 4 electrons to form covalent chemical bond with other atoms. I live in air along with two molecules of oxygen as carbon dioxide(CO₂).
Fixation: algea and terrestrial green plants take me as carbon dioxide from the external environment and convert me into polysacchride as their food in the process of photosynthesis.
Respiration: the consumers obtain the food prepared by the plants and obtain energy from it and again release me in the form of carbon dioxide.
Decomposition: in the decomposition process the animal, plant and human dead and decaying waste is converted from highly complex molecules to less complex molecules, i get produced along with two oxygen molecules (CO₂) in this process.
Fossil fuels: burning of fossil fuels like coal and petroleum leads to again my release as CO₂.