Question

On what basis did Mendeleev classified the elements?

Answer 1

Hint: All the matter present in our surroundings is made up of basic units which are known as elements. Due to the advancement of technology, more elements were discovered, so there is a need for the periodic classification of elements and finally a periodic table is formed to classify all the elements.

Complete answer:
Let us first understand the periodic table. Basically, a periodic table is a table to classify all the elements in which the elements are present on the basis of the atomic number.
Many scientists gave their ideas for the rearrangement of the elements in a table.
i.Dobereiner's Triads- It was first observed by Johann Doberiener in \[1800\] in which the elements are arranged on the basis of their properties. Group consisting of three elements (triads) that have similar chemical and physical properties. Properties of the middle element were also halfway of both the elements. He called this grouping the Law of Triads. Later, it was found this law was not true for every element. Hence it was not successful.
ii.Newland’s Octave- After the failure of Doberiener’s Triads, in \[1865\] John Alexander Newland gave the law of octaves. Every element is arranged in ascending order of their atomic weights. Every \[{8^{th}}\] element of a row has similar properties to that of the first element of that row. This law also was not true for every element. Hence, it was not successful.
iii.Mendeleev’s Periodic table- The real development of arrangement of elements in the periodic table took place after Mendeleev's Periodic table. He classified the elements on the basis of the atomic masses. His law states that “the properties of an element are the periodic function of their atomic masses. He arranged the elements in periodic (horizontal rows) and groups (vertical column). The elements in the groups have similar properties.

Note:
There are some limitations of Mendeleev's Periodic table such as it does not provide a clear idea about the structure of an atom. If the elements are arranged in a group, their atomic weights are reversed several times. Nowadays, the Modern periodic table is formed in which elements are arranged in the order of their atomic numbers. Presently, there are a total \[118\] elements known to us.