Answer:
K⁺ and NO₃⁻ are the spectator ions.
Explanation:
First, we will consider the molecular equation because is the easiest to balance.
K₂CrO₄(aq) + Ba(NO₃)₂(aq) → BaCrO₄(s) + 2 KNO₃(aq)
Then, we will write the full ionic equation, which includes all the ions and the molecular species.
2 K⁺(aq) + CrO₄²⁻(aq) + Ba²⁺(aq) + 2 NO₃⁻(aq) → BaCrO₄(s) + 2 K⁺(aq) + 2 NO₃⁻(aq)
Finally, we will write the net ionic equation, which includes only the ions that participate in the reaction and the molecular species. The missing ions are the spectator ones.
CrO₄²⁻(aq) + Ba²⁺(aq) → BaCrO₄(s)