Question

What is the main difference between mendeleev’s periodic law and modern periodic law?
Which elements have been discovered in the place of Eka-boron and Eka-aluminium.

Answer 1

Eka - boron = Scandium

Eka - aluminium = Gallium

mendeelev arranged the elements in the order of increasing atomic mass while modern periodic table has elements arranged in increasing order of atomic number. mendeelev's periodic table has 8 groups while modern periodic table has 18 groups. mendeelev's periodic table has subgroups but modern periodic table doesn't have subgroups.