The tendency of an element to react is closely related to
a. its atomic mass.
b. attractions between its atoms.
c. the number of valence electrons in atoms of the element.
d. the ratio of protons to neutrons in atoms of the element

The tendency of an element to react is closely related to the number of valence electrons in atoms of the element. 

The valence electrons are what determine how an atom would bond, and when it would bond, and also its reactivity toward other atoms. 

Man i dont know this answer