Write down the electronic configuration of the following:

(i) $^{27}_{13}\text{X}$,

(ii) $^{35}_{17}\text{Y}$.

Write down the number of electrons in X and neutrons in Y and the formula of the compound formed by X and Y.

(i) $^{27}_{13}\text{X}$ = [2, 8, 3] ; Number of electrons in X = 13

(ii) $^{35}_{17}\text{Y}$ = [2, 8, 7] ; Number of neutrons = A - Z = 35 - 17 = 18

Valency of $^{27}_{13}\text{X}$ = [2, 8, 3] = 3 positive

Valency of $^{35}_{17}\text{Y}$ = [2, 8, 7] = 1 negative.

Formula of the compound:

$\text{X}^{3+} \phantom{\nearrow} \text{Y}^{1-} \\[0.5em] \overset{\phantom{3}{3}}{\text{X}} \space {\searrow}\mathllap{\swarrow} \space \overset{1}{\text{Y}} \Rightarrow \underset{\phantom{1}{1}}{\text{X}} \space {\searrow}\mathllap{\swarrow} \space \underset{3}{\text{Y}} \\[0.5em]$

So, we get the formula as $\bold{XY}_\bold{3}$