Who introduced the term ‘triads’ in the classification of elements?
Show answer & explanation
Correct answer: D
Explanation
The correct answer is option 4 i.e. Johann Wolfgang Döbereiner.
Johann Wolfgang Döbereiner, a German chemist, introduced the concept of ‘triads’ in the early 19th century (around 1817). Döbereiner observed that certain groups of three elements (triads) had similar chemical properties, and the atomic mass of the middle element was approximately the average of the other two. For example, calcium, strontium, and barium formed one such triad. This was one of the earliest attempts to classify elements based on their properties and atomic masses, laying groundwork for the development of the modern periodic table by highlighting periodic relationships among elements.
Other Options:
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John Newlands – Known for the Law of Octaves, arranging elements by atomic weight in groups of eight, not triads.
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AEB de Chancourtois – Created the telluric screw or early periodic arrangement based on atomic weights, but didn’t use the term triads.
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Dmitri Mendeleev – Developed the Periodic Table, but triads were an earlier classification before his work.