How does atomic mass indicated element reactivity?

Answer 1

There is no good correlation lies between the element reactivity and the atomic mass.

Answer 2

Atomic Mass does not directly indicate an element's reactivity. Reactivity is primarily determined by the number of electrons in the outer shell of an element (valence electrons). Elements with a full or nearly full outer shell (noble gases) are generally unreactive, while elements with few electrons in the outer shell (alkali metals) are highly reactive.