Question

An element A forms an oxide A₂O₅.
(a) What is the valency of element A ?
(b) What will be the formula of chloride of A ?

Answer 1

(a) Element A forms an oxide A₂O₅. Crossing the valencies, we can see that the valency of O (oxide) is −2 and that of element A is 5.

(b) Formula of chloride of A:
$\begin{array}{ccc}\mathrm{Element}/\mathrm{Ion}& \mathrm{A}& {\mathrm{Cl}}^{-}\\ \mathrm{Valency}& 5& -1\end{array}$
Formula of the chloride of element A can be worked out by crossing over the valencies. Thus, the formula is ACl₅.