Question

What are the achievements of Mendeleev’s periodic table? What was the basis of the classification of elements in it?

Answer 1

Hint: We will start by giving a short introduction about Mendeleev. Then move further to his periodic table and basis of classification. Mandeleev introduced the concept of the triads, i.e. grouping elements together based on their similarity of properties.

Complete step by step solution:
Dimitri Mendeleev was a Russian scientist. In 1869 he noted that repeating patterns of behaviour could be seen in the way elements combined with each other. He is recognized as the father of the modern periodic table.
Mendeleev’s table contained all the known elements in order of increasing relative atomic mass. Each row contained elements with the same joining power, and he swapped elements to suit this pattern. He included “holes” in his table for as yet undiscovered elements and predicted their properties.
Mendeleev made detailed predictions about the properties of some undiscovered elements, based on the gaps in his periodic table. There would be strong support for Mendeleev’s table of elements with these properties. For example: Eka-aluminium, Eka-boron, Eka-silicon
Also, the properties of Eka-aluminium predicted by Mendeleev and those of element gallium were almost the same.
When noble gases were discovered, they could be placed in a new group without disturbing the order.
The formula of the hybrids and oxides formed by an element were treated as one of the basic properties of an element for its classification.

Note:
Dmitri Mendeleev's detailed prediction in 1871 of the properties of three as yet unknown elements earned him enormous prestige. Mendeleev's periodic table is, based on the relation of properties of elements as dependent on the atomic weight of elements. But Modern periodic table considers atomic numbers as the fundamental property that decides the properties of elements. Modern periodic table does correct defects of the Mendeleev's periodic table.