Write the molecular formula for the compound Iron $\left(\mathrm{III}\right)$ sulphide.

Write the molecular formula for the compound mercury $\left(\mathrm{II}\right)$ chloride.

Write the molecular formula for the compound magnesium $\left(\mathrm{II}\right)$ acetate.

Write the molecular formulae of all the compounds that can be formed by the combination of following ions:

${\mathrm{Cu}}^{2+}, {\mathrm{Na}}^{+}, {\mathrm{Fe}}^{3+}, {\mathrm{Cl}}^{-}, {{\mathrm{SO}}_4}^{2-}, {{\mathrm{PO}}_4}^{3-}$.

Write the cation and anion present (if any) in the following compound:

${\mathrm{CH}}_3\mathrm{COONa}$

Write the cation and anion present (if any) in the compound: $\mathrm{NaCl}$

Write the cation and anion present (if any) in the compound: ${\mathrm{H}}_2$

Write the cation and anion present (if any) in the compound: ${\mathrm{NH}}_4{\mathrm{NO}}_3$.

Give the formula of the compound formed from the calcium and fluorine.