Question

Who is Dobereiner and Mandeleeff?What did they discovered and in which year they discovered.

if you know then only answer
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Answer 1

Answer:

In the year 1829 johnn Wolfgang dobereiner discovered the existence of families of elements with similar chemical properties because they always seemed to be three elements in these families he called them triads

Explanation:

mendeleev drew the table he had envisioned while arranging these cards of atomic data he discovered what is called the periodic law when he arranged the elements in the order of increasing atomic mass the properties were repeated