Question

Why did Mendeleev left some gaps in his periodic table?

Answer 1

Part 1: Mendeleev's Periodic Table

1. Mendeleev arranged the 63 elements known at that time in the increasing order of their atomic masses.
2. He proposed that the properties of elements are a periodic function of their atomic masses.

Part 2: Gaps in the periodic table

1. Mendeleev left some gaps in his periodic table so as to place elements that were not dis discovered at that time.
2. Later, it was found that he was correct and the newly discovered elements had the properties predicted by him.
3. Such elements were easily placed in his periodic table without disturbing the arrangement of other elements.