Question

when and how Mosely arranged the elements?
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Answer 1

Answer:

When Moseley arranged the elements in the periodic table by their number of protons rather than their atomic weights, the flaws in the periodic table that had been making scientists uncomfortable for decades simply disappeared.

Explanation:

1913

Using atomic number instead of atomic mass as the organizing principle was first proposed by the British chemist Henry Moseley in 1913, and it solved anomalies like this one. Iodine has a higher atomic number than tellurium - so, even though he didn't know why, Mendeleev was right to place it after tellurium after all!