During a chemical reaction, atoms react with each other to form new products. Atomic bonds in reactants are broken and new ones are formed for creating new products.
If atoms from two different elements react with each other, a compound is formed. During such a reaction, electrons from atoms might be shared or transferred to form new chemical bonds. For example, sulfur reacts with iron when heated together to form iron sulfide, a compound.
Atoms that react with each other in a chemical reaction are called reactants. The atoms that are produced in the reaction are called products. There are no new atoms that are created or destroyed during a chemical reaction. The atoms that are in the products come from the reactants.