Question

Two elements X and Y have the following electronic configurations $X=1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^2$ and $Y=1s^{2}2s^{2}2p^{6}3s^{2}3p^5$. The formula of the compound formed by the combination of X and Y is :

• A. $X{Y}_2$
• B. $X_5{Y}_2$
• C. $X_2{Y}_5$
• D. $X{Y}_5$

Answer 1

Answer: (A)

$X{Y}_2$

X has a stable electronic configuration, with all the orbitals filled completely. For it to retain that stable configuration, it has to lose 2 electrons from its valence orbital 4s, thus, its valency is 2. While Y has one unpaired electron in 3p orbital which is highly reactive. So, 1 electron from Y contributes to the reaction, thus, valency of Y is 1.

$X^2{Y}^1$ $⟹$ $X{Y}_2$.