How could the Modern Periodic Table remove various anomalies of Mendeléev’s Periodic Table?

(i) The modern periodic table is based on atomic number, while Mendeleev’s periodic table was based on atomic mass.So there was no need for keeping more than one element in one slot.
(ii) The isotopes of an element have the same number of protons (or atomic number). So they are alloted the same position in the modern periodic table.Hence the position of isotopes is defined in modern periodic table

(iii)In Modern periodic table elements are classified according to their electronic configuration into different blocks. Elements having same valence electron are kept in same group.Elements having same number of shells were put under the same period.Thus, various anomalies (irregularity) which were seen in Mendeleev’s table due to the arrangement according to atomic masses were overcome by the Modern Periodic table.

(iv)Hydrogen has been alloted special position, i.e., it is placed at the top of alkali metals in the first group.