Which of the following is a defect in Mendeleev’s periodic table

(i) Position of hydrogen   (ii) Grouping of elements

(iii) Anomalous pairs        (iv) Position of isotopes

Defects in Mendeleev’s periodic table is

Position of hydrogen as 3 isotopes are available with different masses.

Grouping of elements as transition and normal elements were placed together.

Anomalous pairs with abnormal arrangements of atomic masses.

Position of isotopes as there was no space to place isotopes of different elements.