The number of electrons lost in the following change is $\mathrm{Fe} + {\mathrm{H}}_2\mathrm{O} \stackrel{ }{\to } {\mathrm{Fe}}_3{\mathrm{O}}_4 + {\mathrm{H}}_2$

$$\begin{gathered} 3 \mathrm{Fe} + 8{\mathrm{e}}^{-} \stackrel{ }{\to } {\left({\mathrm{Fe}}^{8/3+}\right)}_3 \\ 2{\mathrm{H}}^{\oplus } \stackrel{ }{\to } {\mathrm{H}}_2 + 2{\mathrm{e}}^{-} \times 4 \\ \mathrm{\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_} \\ 3\mathrm{Fe} + 4{\mathrm{H}}_2\mathrm{O} \stackrel{ }{\to } {\mathrm{Fe}}_3{\mathrm{O}}_4 + 4{\mathrm{H}}_2 \\ \mathrm{\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_} \end{gathered}$$

The number of electrons lost or gained is 8.