Question

Why could no fixed position be given to hydrogen in Mendeleev's periodic table?

 

Answer 1

Mendeleev's periodic law could not assign a fixed position to hydrogen in the periodic table because hydrogen resembled both alkali metals (Group 1) and halogens (Group 17) in some of its properties. Hydrogen reacts with  metals to form ionic compounds called hydrides and also with non-metals to form covalent compounds.