Explain why is sodium less reactive than potassium.

Explanation

Down the group `(darr)`, `IE_(1)` decreases, hence `IE_(1)` of potassium `(496 kJ "mol"^(-1))` is less that of sodium `(520 kJ "mol"^(-1))`. Moreover, `E^(ө)K_(aq)^(o+)//K_((s))=-2.925 V` is more negative than `E^(ө)Na_(aq)^(o+)//Na_((s))=-2.714 V`. Hence sodium is less reactive than potassium.