Final answer:
Spectator ions are chemically inert ions in a chemical reaction that remain unchanged and are not included in the net ionic equation, demonstrating only the reactive parts of the reaction.
Step-by-step explanation:
When certain ions within a reaction are termed chemically inert, they do not take part in the chemical change. These ions are known as spectator ions because they remain in the solution unchanged before and after the reaction. An example of this occurs when aqueous solutions of CaCl2 and AgNO3 are mixed. In this reaction, the Ag+ (aq) and Cl− (aq) ions combine to form a precipitate of AgCl (solid), while the Ca2+ (aq) and NO3− (aq) ions do not react and are thus spectator ions. When writing the net ionic equation, these spectator ions are not included, as the equation represents only the ions and compounds that actively participate in the reaction.