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The first attempt to classify elements systematically was made by :
C.Lother Meyer

Last updated date: 14th Apr 2024
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MVSAT 2024
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All existing matter in our surroundings is made up of basic units known as elements. Presently, there are 118 elements known to us. It was observed that elements show periodicity in their properties. Many tables were made to arrange the elements in an ordered manner based on their characteristics to study the properties of elements in a fixed pattern. Many attempts were made to classify elements but not all were successful.

Complete step by step answer:
-The first attempt to classify elements systematically was made by Dobereiner.
-In 1817, Johann Wolfgang Dobereiner’s observations of the alkaline earths, namely that of strontium had properties that were immediate to those of calcium and barium.
-In 1829, he had found other groups of three elements, whose physical properties were similarly related.
-Some groups were identified as having three elements each. So he called three groups “ triads”. Only three triads could be identified from the elements discovered at that time.
-The properties of the elements followed trends in which the value of the middle element of the triad was in between those of end members.
-The triad was the earliest atomic weight classification of the elements.

Hence, option D is correct.

Additional information
Limitations of the triad were:
1.He could find only three triads i.e. total of 9 elements only.
2.However total numbers of elements were more than that of those encompassed in Dobereiner’s triad.
3.The law of triads was rejected because Doberiener failed to arrange all the known elements in the form of triads.

He arranged the three elements in a triad in an increasing order of atomic mass and showed that the atomic mass of the middle element was approximately equal to the mean of the atomic masses of the other elements.

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