Question

Two elements $X$ and $Y$ have following elecronic configuration:

$X=$ $1s^2,2s^2,2p^6,3s^3,3p^6,4s^2$ and
$Y=$ $1s^2,2s^2,2p^6,3s^2,3p^5$

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. $X_{2}Y$

Answer 1

The correct option is A $X{Y}_2$

Electronic configuration of $X$ is:

$X=1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^2$ has 2 electrons more than stable configuration. So this can be written as $X^{2+}$ after removing 2 eletrcons.

Electronic configuration of $Y$ is:

$Y=1s^{2}2s^{2}2p^{6}3s^{2}3p^5$ has 1 electron less than stable configuration. So this can be written as $Y^{-}$ after gaining 1 electron

$X^{2+}+2Y^{-}=X{Y}_2$

$2$ ions of element $Y$ combine with $1$ ion $X$ to give $X{Y}_2$ .

The resulting molecule will be stable and will have no net charge.