Question

explain the following

Answer 1

limitation of Mendeleev periodic table

position of isotope could not be explain isotope where Discover long after Mendeleev has proposed his periodic classification of element


wrong order of atomic number in sub could not be explains Cobalt comes before Nickel where the Cobalt atomic mass is 58 . 9 where the Nickel atomic mass is 58.7


hydrogen was not assigned correct position hydrogen has property of both alkali metal and halogen



I could not answer the questions it is possible had an element with atomic mass 3 placed between hydrogen and helium

Answer 2

Mendeleev guessed that there more elements which are not found yet. so he left the gaps.

Mendeleev couldn't identify or place h2