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Wednesday 13 February 2019

Introduction of Periodic Table




Intro:

Understanding Chemistry without understanding the elements is impossible. So, Periodic Table has been introduced to understand the properties of elements easily. Over more than 100 years Periodic Table has helped to systematize the properties of elements. "Periodic Table provides a basic framework to study the periodic behavior of physical and chemical properties of elements as well as their compounds".

Background:

It was Al-Razi who made a memorable contribution in the history of periodic table. He tried to classify elements based on their Physical and Chemical properties of substances. Dobereiner is another German chemist who also made a significant contribution to this field. In 1829, he arranged elements, of that time, in groups known as Triads. He put three elements in each group with similar properties. Then in 1864, an English Chemist, Newland classified 62 elements of that time in the ascending order of their atomic masses. Newland observed that every eighth element had some common properties with the first one. This principle on which Newland's classification is based was called the Law of Octaves.
In 1871, Russian Chemist, Dimitri Mendeleev, came up with his model. He had a great contribution in arranging the elements in regular order. He is also known as the father of modern periodic table.
He was the first scientist who arrange the elements in a proper way. In Mendeleev's periodic table elements of similar properties were put in eight vertical columns known as Groups and the horizontal rows are known as Periods.  
Mendeleev also arranged elements according to their ascending atomic mass. While arranging the element he observed that elements with similar chemical properties appeared at regular in interval. This observation was known as Periodic Law. He also predicted and left gaps for the undiscovered elements at that time. For example, germanium was not discovered at that time, but Mendeleev was confident and predicted its position in the periodic table and after few years Germanium was found and this was remarkable correction of Mendeleev's predictions. Below is Mendeleev's periodic table:
 

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