Question

If the aluminium salt of an anion X is Al₂X₃, what is the valency of X ? What will be the formula of the magnesium salt of X ?

Answer 1

Valency of X in the aluminium salt Al₂X₃ can be worked out as follows (we know that valency of Al is 3):

$\begin{array}{ccc}\mathrm{Element}& \mathrm{Al}& \mathrm{X}\\ \mathrm{Valency}& 3& 2\end{array}$

Thus, it is clear that the valency of X is two.

Formula for the magnesium salt of X can be worked out as follows:
$\begin{array}{ccc}\mathrm{Element}& \mathrm{Mg}& \mathrm{X}\\ \mathrm{Valency}& 2& 2\end{array}$
Crossing the valencies gives us the formula of the magnesium salt of X i.e. MgX.