Name: Occurrence of Noble Gases
Uploaded: 2019-07-19
Duration: 9 min 27 s
Description: Inert gases are also known as “noble” because they were assumed to be non-reactive since they have filled valence shells. Let’s see the video.

Question

Prepare the biographical notes of scientists related to the classification of elements.

Accepted Answer

Dobereiner gave a notable contribution to the classification of elements. He formed small groups of three elements showing similar properties. These groups were called Triads. It helped in finding the relationship between atomic mass and properties of elements. All elements could not be classified into triads, which was the limitation of this classification.

In $1865$ when Newlands arranged the known $56$ elements in the increasing order of atomic mass, he found that properties of the eight elements are the repetition of those of the first element. He compared this to the seven notes of music. This law is known as the Law of Octaves. But one of the noted limitations of this was that the elements with higher atomic mass did not obey this rule.

In $1789$ , Lavoisier classified the elements into metals and non-metals. But he was not able to classify metalloids that show the properties of both metals and non-metals. This was one of the limitations of this classification.

It was the Russian scientist Dmitri Ivanovich Mendeleev who created a table for the first time for the classification of elements. Later, Mendeleev came to be known as the father of the periodic table. This periodic table which became a milestone in the history of the classification of elements had $63$ elements when it was created. Mendeleev arranged these elements in the table in the increasing of their atomic masses. But, there are some limitations in the Mendeleev's periodic table.

Henry Moseley, through his experiments, proved that the properties of elements depend on their atomic number. According to this, the elements are arranged in the periodic table in the increasing order of their atomic numbers. This table is also known as the 'Modern Periodic Table'.

Kerala Board Solutions for Chapter: Periodic Table, Exercise 3: Extended activities

Kerala Board Chemistry Solutions for Exercise - Kerala Board Solutions for Chapter: Periodic Table, Exercise 3: Extended activities

Questions from Kerala Board Solutions for Chapter: Periodic Table, Exercise 3: Extended activities with Hints & Solutions

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