Hydrogen occupies a unique position in modern periodic table. Justify the statement.

Explanation

Hydrogen occupies a unique position in the modern periodic table due to the following reasons :
(a) Both hydrogen and alkali metals have similar outer electronic configuration because both have one electron in their valence shell. Hence, some of the properties of hydrogen are similar to those of alkali metals and hence, it can be placed in group along with alkali metals.
(b) Both hydrogen and halogens have similar outer electronic configuration (both have one electron less than the nearest inert gas configuration). Hence, some of the properties of hydrogen are similar to those of halogens and therefore, it can be placed in group 17 along with halogens.
(c) In some properties, it differs from both hydrogen and halogens, e.g., the oxide of hydrogen, i.e., `H_2 O` is neutral but the oxides of alkali metals (i.e., `Na_(2) O, K_(2) O` etc. ) are basic while those of halogens (i.e., `CI_(2) O_(7) , Br_(2) O_(5) , I_(2) O_(5)` etc. ) are acidic.