The question requires us to comment on what happens to the atoms in a chemical reaction considering the Law of Conservation of Mass.
The Law of Conservation of Mass states that mass is neither created nor destroyed in a chemical reaction. In other words, although the atoms in the reactants rearrange in order to form the products, the mass of both products and reactants must be the same.
Therefore, we can say that, considering the Law of Conservation of Mass, the atoms at the start of a chemical reaction are rearranged compared to the atoms at the end of the reaction, but the mass of reactants and products do not change.