Photosynthesis is the process of fixing atmospheric carbon dioxide by green plants (which contain chlorophyll), in the presence of sunlight, with elimination of oxygen and formation of variated organic compounds (carbohydrates, lipids, proteins).The general ecuation of photosynthesis can be written as:
6CO₂ + 6H₂O + sunlight -----> C₆H₁₂O₆ + 6O₂
Oxygen in normal conditions of pressure and temperature is written as O₂ which is also known as diatomic molecular oxygen, called dioxygen. The 2 of the general formula of O₂ is the oxygen index.