Question

Write the formula of the compound chromium sulfate.

Answer 1

The symbol of chromium is ‘$\mathrm{Cr}$’, having a valency of 3⁺.

The formula of sulfate is ‘${\mathrm{SO}}_4$’ with valency 2^-.

Step 1 –

Write the formula of chromium sulfate:

Symbol Valency

Chromium $\mathrm{Cr}$ 3⁺

Sulfate ${\mathrm{SO}}_4$ 2^-

Step 2 –

Write each symbol with its valency:

${\mathrm{Cr}}^{3+}$ ${{\mathrm{SO}}_4}^{2-}$

Step 3 –

Interchanging the valencies:

$$\begin{gathered} \mathrm{Cr}{\mathrm{SO}}_4 \\ \searrow \swarrow \\ {3}^{+}{2}^{-} \end{gathered}$$

The formula of the compound would be ${\mathrm{Cr}}_2{\left({\mathrm{SO}}_4\right)}_3$.