A chemical equation is said to be balanced when the number of atoms of each element on the reactant side is equal to the number of atoms of those elements on the product side.
The process of photosynthesis involves carbon dioxide and water, which reacted together to form glucose and oxygen. The balanced equation for photosynthesis is given below:
6H2O + 6CO2 = C6H12O6 + 6O2.
Looking at this chemical equation, you will discover that: there are 12 atom of hydrogen, 18 atoms of oxygen and 6 atoms of carbon on both sides of the equation.