Which atomic property is more suitable for classification of elements ? Why ?

Which property of an element taken for classification of elements by mendeleev ?

Give reason for the need of classification of element .

The earliest classification of elements is attempted by :

Correlate various tables proposed on classification of elements.

The scientist____ is appreciable because his attempts gave a clue that atomic weights could be correlated with properties of elements and led to rigorous classification of elements and the modern periodic table of elements.

Which of the following statements are correct for classification of elements? I. The properties of elements are periodic function of their atomic numbers. II. Non-metallic elements are less in number than the metallic elements. III. The first ionisation energies of elements along a period do not vary in a regular manner. IV. The ground state electronic configuration of Pd (Z = 46 ) is [Kr] 4 d 5s^(2) .