[1] For example, in the reaction of aqueous solutions of sodium carbonate and copper(II) sulfate: The Na+ and SO2−4 ions are spectator ions since they remain unchanged on both sides of the equation.
They simply "watch" the other ions react and does not participate in any reaction, hence the name.
[1] They are present in total ionic equations to balance the charges of the ions.
[1] So, the net ionic equation only shows the ions which reacted to produce a precipitate.
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