Elements X, Y and Z have 3, 7 and 6 electrons in their valence shells respectively. Write the formula of the compound formed between :

(a) X and Y

(b) X and Z

(a) Valency of X is +3 and Y is -1. Formula of the compound formed between X and Y is :

$\text{X}^{3+} \space \text{Y}^{1-} \\[1em] \overset{\phantom{22}{3}}{\text{X}} \space {\swarrow}\mathllap{\searrow} \space \overset{1}{\text{Y}} \Rightarrow \underset{\phantom{2}{1}}{\text{X}} \space {\swarrow}\mathllap{\searrow} \underset{{3}}{\text{Y}} \\[1em] \text{X}\text{Y}_3$

∴ Chemical formula of the compound formed between X and Y is XY₃

(b) Valency of X is +3 and Z is -2. Formula of the compound formed between X and Z is :

$\text{X}^{3+} \space \text{Z}^{2-} \\[1em] \overset{\phantom{22}{3}}{\text{X}} \space {\swarrow}\mathllap{\searrow} \space \overset{2}{\text{Z}} \Rightarrow \underset{\phantom{2}{2}}{\text{X}} \space {\swarrow}\mathllap{\searrow} \underset{{3}}{\text{Z}} \\[1em] \text{X}$2\text{Z}3

∴ Chemical formula of the compound formed between X and Z is X₂Z₃