Carbon dioxide

Carbon dioxide is one of the oxides of carbon, containing one carbon and two oxygens. Carbon dioxide occurs naturally in the atmosphere at approximately 412 parts per million.

Solid CO2 is known as "Dry Ice."

It is an essential component of photosynthesis, and thus vital for plants (6 CO2 + 6 H2O -> C6H12O6 + 6 O2)

It is also the output of cellular respiration (C6H12O6 + 6 O2 -> 6 CO2 + 6 H2O)

CO2 is denser than air and is one of the results of burning hydrocarbons.