Answer
a) $PtCl_2$, $PtCl_4$
b) $PtS$, $PtS_2$
Work Step by Step
The ions chloride $Cl^-$ and sulfide $S^{2-}$ would form the following compounds:
a) $Pt^{2+}$: balancing the charges: 1 $Pt^{2+}$ and 2 $Cl^-$: $PtCl_2$
$\qquad\qquad\qquad\qquad\qquad\quad\quad\ \ $ 1 $Pt^{2+}$ and 1 $S^{2-}$: $PtS$
b) a) $Pt^{4+}$: balancing the charges: 1 $Pt^{4+}$ and 4 $Cl^-$: $PtCl_4$
$\qquad\qquad\qquad\qquad\qquad\quad\quad\ \ \ \ \ \ $1 $Pt^{4+}$ and 2 $S^{2-}$: $PtS_2$
