Why did Mendeleev place Iodine after Tellurium on his periodic table?

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Why did Mendeleev place Iodine after Tellurium on his periodic table?

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The “atomic mass” of tellurium is higher than that of iodine as displayed on modern periodic tables, but Mendeleev placed Tellurium 1st due to the way atomic masses are calculated, based on a weighted average of all of an element’s common isotopes.