Question

why could no fixed position be given to hydrogen in mendeleev's periodic table​

Answer 1

No fixed position was given to HYDROGEN in Mendeleev Periodic Table.

It is because it predicted the values of both metals and non metals.

and hence he was unable to give a fixed position to Hydrogen.

hope this helps...

Answer 2

Hydrogen can form diatomic molecules just like halogens. It has a single electron in the outermost shell this means that it could easily gain an electron or loose an electron like alkali metals to achieve the noble gas configuration of helium.

Due to this dual nature of hydrogen, Mendeleev could not assign a fixed position to hydrogen in his periodic table.