Question

Question 1
How could the modern periodic table remove various anomalies of Mendeleev's periodic table?

Answer 1

Various anomalies of Mendeleev’s periodic table was removed as follows in the modern periodic table:
$\to$ Elements are arranged in the increasing order of their atomic number in modern periodic table, thus there was no need for keeping more than one element in one slot.
$\to$ In the modern periodic table there was no problem for the placement of isotopes, as isotopes have different atomic masses but same atomic numbers.
$\to$ Elements having same valence electron are kept in the same group.
$\to$ Elements having same number of shells were put under the same period.