Question

out of atomic mass and atomic number what determined the chemical reactivity of an element and give reason and explain it briefly??

Answer 1

I think it is atomic number because valency and valence electrons of an atom plays important role in the reactivity. They help in sharing,gaining or losing electrons,i.e.,for forming ionic or covalent bond between the the atmosphere of different element.
Therefore,the atomic number determines the chemical reactivity of an element .

Answer 2

i guess Chemical Reactivity depends on the atomic number (not on mass),,,and on atomic radius of element.

No. of electron have effect on reactivity of elements,,and their size,,larger the size ,,higher the reactivity!!!