Periodic classification of element there are 118 element in a Periodic Table Dobereiner
In 1817 John Dobereiner a German chemist he tried to arrange element similar properties into group age group of 3 element calledTraids he arranged 3 element in the order of atomic masses the atomic mass of the middle element was roughly the average of the atomic masses of the two elements.
Limitations of Dobereiner classification
1 he was failed to arrange all the elements in the foam of trains having similar chemical properties
2 he could identify only three triads from the element know that time
New land s law of octaves
John new land arrange the element in the order of increasing atomic masses he started with the lowest atomic mass and ended at throium
During his period only 56 elements were discovered he found that eight element had properties similar to that of the first he called it law of octaves
Limitations of new land classification
Law of octaves was applicable only upto calcium yes after calcium every 18th element did not passes properties similar to that of first
It was assumed by newland that only 56 elements exist in nature and no more elements would be discovered in the future but letter on serial new elements were discovered was properties did not fit into the law of octaves
3 newland adjust in two elements in the same slot but also put some unlike elements under the same note.
By कशिश कुमार त्रिपाठी