Answer: There are 2 chlorine atoms on reactant side and two chlorine atoms on product side.
Step-by-step explanation:

The given balanced equation follows the law of conservation of mass, which states the mass on product side must be equal to the mass on reactant side.
This can happen only if the number of atoms are same on both sidesof the arrow. There are 2 chlorine atoms in
and 2 chlorine atoms in
