Question

Write the formula of the compound ferrous sulphide.

Answer 1

The symbol of iron(ferrous) is ‘$\mathrm{Fe}$’, having a valency of 2⁺.

The symbol of sulphur is ‘$\mathrm{S}$’ with valency 2^-.

Step 1 –

Write the formula of sodium zincate:

Symbol Valency

Iron $\mathrm{Fe}$ 2⁺

Sulphur $\mathrm{S}$ 2^-

Step 2 –

Write each symbol with its valency:

${\mathrm{Fe}}^{2+}$ ${\mathrm{S}}^{2-}$

Step 3 –

Interchanging the valencies:

$$\begin{gathered} \mathrm{Fe}\mathrm{S} \\ \searrow \swarrow \\ {2}^{+}{2}^{-} \end{gathered}$$

The formula of the compound ferrous sulphide would be ${\mathrm{Fe}}_2{\mathrm{S}}_2$ $\Rightarrow$$\mathrm{FeS}$.