Why isotopes were not given any place in the mandeleev's periodic table?

Dear student,

Isotopes are the atoms of the same element having different atomic masses. Therefore, according to Mendeleev’s classification these should be placed at different places depending upon their atomic masses.
Because modern periodic table is arranged according to the atomic number of the elements. Whereabout isotopes have same atomic number (but different atomic mass). And that's why isotopes don't occupy an indiviual position in periodic table.
For example, hydrogen isotopes with atomic masses 1,2 and 3 should be placed at three places. However, isotopes have not been given separate places in the periodic table because of their similar properties.


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Becos who could not explain or understand the existence of isotopes
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Becos he
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