So, if we have calcium carbonate and we heat it, it breaks down to produce calcium oxide and carbon dioxide. Gethin: OK, I know you're poised with your pen and your flip chart. But, before that ...

The atoms in the reactants are: 1 calcium atom, 2 chlorine atoms, 2 sodium atoms, 2 hydrogen atoms, 2 carbon atoms, and 6 oxygen atoms The atoms in the products are: 1 calcium atom, 2 chlorine atoms, ...