Question

What do you mean by fundamental property ?

Answer 1

According to Mendeleev fundamental property of an element is atomic mass.
Mendeleev arranged the known elements according to increasing order of their atomic masses.
The elements, if arranged according to their atomic weights show an evident periodicity of properties. like if we going down a group then atomic mass increases and due to this electronegetivity and ionisation energy decreases.
If we move in periods, atomic radii decreases and due to this electronegativity increases periodically.
So all properties are the periodic function of their atomic masses.