Hence, it was placed in 1st A group nd 6th B group nd could not be given a fixed position in mandleev\’s periodic table. It is so becoz hydrogen has 1 valence electrons in outermost shell. So, according to modern periodic table, hydrogen can be arranged in halogen family.
Because it shows few properties of metals and few of non metals so it is kept in separate group in modern periodic table
That is only the limitation of modern preoidic table ……and of mendeleevs too