Question

Electronic configuration of an atom X is (2, 8, 7). It combines with another atom Y having electronic configuration (…, 1).

Write the formula of compound formed?

Answer 1

• X = $2,8,7$. It is a non-metal with valency $1$.

$\mathrm{X}+{\mathrm{e}}^{-}\to {\mathrm{X}}^{-}$, it will gain an electron and attain a noble gas configuration.

• Y = $..,1$, it is a metal with valency $1$.

$\mathrm{Y}\to {\mathrm{Y}}^{+}+{\mathrm{e}}^{-}$, it will lose an electron and attain a noble gas configuration.

Part 2: Bond formation

• X and Y have 7 and 1 electrons in their outermost shells respectively so Y loses its one electron and X gains that electron to attain noble gas configuration. A bond generated by the transfer of electrons from one atom present in one element to another is called an Ionic bond. So, a compound formed by X and Y is ionic in nature.
• Reaction between X and Y is ${\mathrm{Y}}^{+}+{\mathrm{X}}^{-}\to \mathrm{YX}$ (Both has valency 1)

Therefore, the chemical formula of a compound of X and Y is YX.