Question

An element B shows valencies of 4 and 6. Write the formulae of its two oxides.

Answer 1

Case i

Valency of B = 4
Valency of O = 2

$\begin{array}{ccc}\mathrm{Elements}:& \mathrm{B}& \mathrm{O}\\ \mathrm{Valencies}:& 4& 2\end{array}$

Formula for the oxide formed by the element B (valency 4) can be worked out by crossing over the valencies of the constituent elements.
Therefore, formula of the oxide of element B is B₂O₄. The formula has a common factor of 2; hence, dividing the formula by the common factor gives us the simplest chemical formula: BO₂.

Case ii

Valency of element B = 6
Valency of O = 2

$\begin{array}{ccc}\mathrm{Elements}:& \mathrm{B}& \mathrm{O}\\ \mathrm{Valencies}:& 6& 2\end{array}$

Formula for the oxide formed by the element B (valency 6) can be worked out by crossing over the valencies of the constituent elements.
Therefore, formula of the oxide of element B is B₂O₆. The formula has a common factor of 2; therefore, dividing the formula by the common factor gives us the simplest chemical formula: BO₃.