Question

what was the basis of classification of elements in modern periodic table

Answer 1

the periodic table is organized on the basis of their
1. atomic numbers.
2. electronic configuration
3. recurring chemical properties

Answer 2

The modern classification is based on the atomic number of the element.   The periodic law state that the physical and chemical properties of the element are the periodic function of their atomic number. Therefore the variation in the properties of element is related with its electronic configuration.

HOPE IT HELP