The table of Mendeleeff was changed but little for thirty years. Its anomalies, as the omission of hydrogen and the rejection of the atomic weight as the deciding factor in such cases as cobalt and nickel, tellurium and iodine, etc., were recognized; but greater knowledge was needed before these could be explained or the underlying law grasped.
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About Dmitri Mendeleev
Dmitri Mendeleev was a 19th-century Russian chemist. Dmitri Ivanovich Mendeleev was a Russian chemist known for formulating the periodic law and creating a version of the periodic table of elements. He used the periodic law not only to correct the then-accepted properties of some known elements, such as the valence and atomic weight of uranium, but also to predict the properties of three elements that were yet to be discovered. Read more on Wikipedia →