Modified Mendeleev's periodic table was given by whom and when?
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Modified Mendeleev's periodic table was given by whom and when?
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Answer:
Explanation:
Mendeleev’s table was arranged according to atomic weight. It was shot full of incongruities. Elements seemed to be arranged in the wrong orders; physicochemical correlations within columns didn’t make sense; the lanthanide elements didn’t seem to belong in any column, although their physicochemical properties were very similar ; and no one could figure out where the undiscovered elements were supposed to go. Chemists had been arranging the elements by atomic weight for a hundred years. Mendeleev’s table was a refinement of the earlier works, with the benefit of some newly discovered elements, and some additional atomic weight determinations.
When the periodic table was arranged by atomic number in 1913, all these incongruities were resolved, and we discovered not only the atomic numbers of elements that were yet to be discovered, but the way to identify the atomic number of ANY element. These two things enabled the discovery of several elements that properly fit into the “gaps” in the table.
It was found that uranium was the element with the highest atomic weight and the highest atomic number of all the naturally occurring elements: this although uranium had been discovered and identified in the eighteenth century. The correlation with atomic number was also critical in identifying two new elements ( unknown at the time ) that were radioactive: technetium and protactinium. The discovery of these two elements was indeed instrumental in the development of nuclear chemistry, and other studies related to radioactivity of uranium and radium