Why alkali metals have high chemical reactivity? How this changes along the group?

Explanation

Alkali metals exhibit high chemical reactivity because of their low ionization enthalpy and their larger size. The reactivity of alkali metals increases from Li to Cs, since the value of ionization energy decreases down the group (Lito Cs). All the alkali metals are highly reactive towards the more electronegative elements such as oxygen and halogens