Give the molecular formula of ferrous chloride.

The valency of magnesium is $2$. Give the valency of the other ion in the following compounds.

i. $\mathrm{MgO}$ ii. ${\mathrm{Mg}}_3{\mathrm{N}}_2$

iii. ${\mathrm{MgCl}}_2$ iv. ${\mathrm{MgCO}}_3$

v. $\mathrm{Mg}{\left({\mathrm{NO}}_3\right)}_2$ vi. $\mathrm{Mg}{\left(\mathrm{OH}\right)}_2$

Write the names of the following compounds.

$$\begin{gathered} \mathrm{i}. {\mathrm{FeCl}}_2 \\ \mathrm{ii}. {\mathrm{CaSO}}_4 \\ \mathrm{iii}. \mathrm{NaCl} \\ \mathrm{iv}. \mathrm{Zn}{\left(\mathrm{OH}\right)}_2 \\ \mathrm{v}. {\mathrm{BaCl}}_2 \end{gathered}$$

Derive the molecular formulae of the following compound stepwise and give their atomicity.

Ammonium sulphate