An element X of valency 3 combines with another element Y of valency 2. What will be the formula of the compound formed?

An element X has a valency of 4 whereas another element Y has a valency of 1. What will be the formula of the compound formed between X and Y?

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

Work out the formula for magnesium hydrogencarbonate.

An element X has a valency of 2. Write the simplest formula for:

(a) bromide of the element

(b) oxide of the element