7. ____ pb(clo₂)₄ + ____ zn(so₄) → ____ pb(so₄)₂ + ____ zn(clo₂)₂

Explanation:

Step1: Balance lead (Pb) atoms

The number of Pb atoms on both sides is already 1, so no coefficient adjustment is needed for Pb - containing compounds for now.

Step2: Balance sulfate ($SO_4^{2 - }$) groups

There are 4 $ClO_2^-$ groups in $Pb(ClO_2)_4$ and 1 $SO_4^{2 - }$ group in $Zn(SO_4)$. To balance the sulfate groups, we need 2 moles of $Zn(SO_4)$ since there are 2 $SO_4^{2 - }$ groups in $Pb(SO_4)_2$.

Step3: Balance zinc (Zn) and chlorite ($ClO_2^-$) groups

After adding a coefficient of 2 for $Zn(SO_4)$, we have 2 Zn atoms on the left - hand side. To balance the Zn atoms on the right - hand side, we need a coefficient of 2 for $Zn(ClO_2)_2$. Also, the number of $ClO_2^-$ groups is balanced as well.

Answer:

1; 2; 1; 2