Final answer:
Ions that do not take part in the reaction and remain in solution are called a. spectator ions. The answer is option a, spectators. These ions are present in the net ionic equation but do not undergo a chemical change.
Step-by-step explanation:
Ions that are present in a solution in which a reaction is taking place but that do not participate in the reaction are called spectator ions.
The correct answer to fill in the blank is option (a) spectators.
Spectator ions are found in solution both before and after the reaction and do not undergo a chemical change during the reaction.
They can be observed in the reaction between sodium chloride and silver nitrate, where the sodium (Na+) and nitrate (NO3−) ions are spectators:
Na+ (aq) + Cl− (aq) + Ag+ (aq) + NO3− (aq) → Na+ (aq) + NO3 (aq) + AgCl (s)
Here, the net ionic equation would only include the ions that participate in the reaction: Ag+ (aq) + Cl− (aq) → AgCl (s), leaving out the spectator ions.