Question

balance the chemical equation using the smallest possible whole number coefficients.
if the coefficient is 1, you may leave it blank.
\square fe_{(s)} + \square s_{8(s)} \
ightarrow \square fes_{(s)}

Explanation:

Step1: Balance sulfur atoms

On the reactant side, there are 8 S atoms in $\text{S}_8$. On the product side, each FeS has 1 S atom, so we need 8 FeS to get 8 S atoms:
$\text{Fe}_{(s)} + \text{S}_{8(s)}
ightarrow 8\text{FeS}_{(s)}$

Step2: Balance iron atoms

Now the product side has 8 Fe atoms (from 8 FeS). So we need 8 Fe atoms on the reactant side:
$8\text{Fe}_{(s)} + \text{S}_{8(s)}
ightarrow 8\text{FeS}_{(s)}$

Step3: Verify balance

Reactants: 8 Fe, 8 S. Products: 8 Fe, 8 S. The equation is balanced. (Coefficient 1 can be left blank, so $\text{S}_8$ can have an empty box)

Answer:

$\boldsymbol{8}$ Fe$_{(s)}$ + $\boldsymbol{1}$ S$_{8(s)}$ $
ightarrow$ $\boldsymbol{8}$ FeS$_{(s)}$