Question

Mendeleev did not use the atomic number as the basis of classification of elements. Mention the reason.

Answer 1

Step 1: Introduction of Mendeleev's periodic table

A systematic arrangement of elements into groups and periods in the order of increasing atomic mass is called Mendeleev's periodic table.

The elements are arranged in order of increasing number of protons in the nucleus is called atomic number.

Step 2: Reason behind the classification of elements

Mendeleev classified elements on the basis of their chemical properties and increasing atomic masses. The protons and neutrons were not discovered when he made the modern periodic table.

So, Mendeleev did not use the atomic number as the basis of the classification of elements.