Question

Why does hydrogen occupy unique position in the periodic table ??

Answer 1

Dear student
Hydrogen occupies a unique position in the modern periodic table due to the following reasons
(i) Both hydrogen and alkali metals have similar outer electronic configuration as both have one electron in the valence shell. Therefore, 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.
(ii) Both hydrogen and halogens have similar outer electronic configuration (both have one electron less than the nearest inert gas configuration). Therefore, some of the properties of hydrogen are similar to those of halogens and hence, it can be placed in group 17 along with halogens.
(iii) In some properties, it differs from both hydrogen and halogens, e.g., the oxide of hydrogen, i.e., H₂O is neutral but the oxides of alkali metals (i.e., Na₂O, K₂O etc.) are basic while those of halogens (i.e., Cl₂O₇, Br₂O₅, I₂O₅ etc.) are acidic.

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