Write the chemical formula of the compound copper [I] sulphide in a step-by-step manner.

The symbol of copper is ‘Cu’, having a valency of 1⁺.

The symbol of sulphide is ‘S’ with valency 2^-.

Step 1 –

Write the formula of copper [I] sulphide:

Symbol Valency

Copper Cu 1⁺

Sulphide S 2^-

Step 2 –

Write each symbol with its valency:

Cu¹⁺ S^2-

Step 3 –

Interchanging the valencies:

$$\begin{gathered} \mathrm{Cu}\mathrm{S} \\ \searrow \swarrow \\ {1}^{+}{2}^{-} \end{gathered}$$

The formula of the compound copper [I] sulphide is Cu₂S.