Question 735f3

May 29, 2015

Their formula will be $X Y$.

Notice that the number of electrons located in their outermost shell varies significantly for the two elements.

On one hand, $X$ has only 2 electrons in its outermost shell. This means that it's easier for $X$ to lose these electrons In order to complete its octet, i.e. have a total of 8 electrons in its outermost shell, than to gain 6 more.

On the other hand, $Y$ has 6 electrons in its outermost shell, which means that it can easily gain two electrons to complete its octet.

Element $X$ can thus form 2+ cations, ${X}^{\textcolor{red}{2 +}}$, and element $Y$ can form 2- anions, ${Y}^{\textcolor{b l u e}{2 -}}$.

When these two elements react, $X$ will lose its 2 valence electrons and $Y$ will take them. The two elements will thus form an ionic compound with the formula

{: (X^(color(red)(2+))), (Y^(color(blue)(2-))) :}} =>X_(color(blue)(2))Y_(color(red)(2)) <=> XY#