1) The question is incomplete. What is the compound which Fe(ClO4)2 reacts with?
It could be one of several salts.
2) Assuming it is Na2S the complete reaction is:
Fe(ClO4)2 (aq) + Na2S(aq) → FeS (s) + 2NaClO4 (aq)
So, the next steps how how to work this problem assuming that reaction.
3) Show the ionic compounds as separate ions.
Fe(2+) (aq) + 2 ClO4(-) (aq) + 2 Na(+) (aq) + S(2-) (aq) → FeS(s) + 2 Na(aq) + 2 ClO4(-) (aq)
That is the total ionic equation.
4) Cancel the ions that appear on both sides of the equation , Na(+) and ClO4(-).
Fe(2+) (aq) + S(2-) (aq) → FeS(s) <-------- this is the net ionic equation
What happens to sodium and perchlorate is that they do not participate in the reaction but remain dissolved which is called "spectator ions".
