If the numbers of each type of atom are different on the two sides of a chemical equation, then the equation is unbalanced, and it cannot correctly describe what happens during the reaction. In this reaction, and in most chemical reactions, bonds are broken in the reactants (here, Cr–O and N–H bonds), and new bonds are formed to create the products (here, O–H and N≡N bonds). A chemical reaction represents a change in the distribution of atoms, but not in the number of atoms. What is different on each side of the equation is how the atoms are arranged to make molecules or ions.
