Question

Why is the atomic number of an element more important than its atomic mass in a contexts of its properties

Answer 1

Atomic number gives the number of protons, which is also the number of electrons, and from that, the number of valence electrons can be deduced. Properties of an element mostly depends on its valence electrons and atomic number .
Like, you can get the valency, atomicity, radius of the atom, electronegativity, IP and so on