Ans.
1. Hydrogen resembles alkali metals. It has one electron in its outermost shell like alkali metals. Its valency is 1 like alkali metals. If roms oxides (H2O) similar to alkali metals (Na2O).
2. Hydrogen also resembles halogens. It is a diatomic molecule (H2) like halogens (F2 , Cl2). Like halogens it requires one electrons to achieve stable electronic configuration similar to halogens.
3. Due to this unique behaviour of hydrogen, it is difficult to assign any definite position to it in the modern periodic table. Generally, it is placed above lithium in the periodic table.
