Element X which is present in group 2 has two valence shell electrons. Therefore, the elements belonging to group 2 have the tendency to loose or transfer two electrons and get oxidized as,
X --------> X²⁺ + 2e⁻
Also, Element Y which is present in group 17 has seven valence shell electrons. Therefore, the elements belonging to group 17 have the tendency to accept one electron from other element and complete its Noble gas configuration as,
Y + 1 e⁻ -------> Y⁻
Hence, formation of compound between the X and Y takes place one when one X element looses two electrons and two Y elements gain those two electrons and form an Ionic bond.
X²⁺ + 2Y⁻ ---------> XY₂
Hence, in this reaction the X is oxidized and Y is reduced. Also, X has acted as reducing agent while Y has acted as oxidizing agent.
