Position of Hydrogen in periodic table

Position of an element in periodic table depends upon its electronic configuration and properties. Hydrogen resembles the elements of group I-A, IV-A and VII-A in some respects. Properties of hydrogen do not completely match any one of the above-mentioned groups. That is why position of hydrogen is still undecided. In the coming lines we will discuss why hydrogen can not be placed in a particular group in the periodic table.

Properties of hydrogen

Electronic configuration

Configuration of outermost shell of hydrogen is same as that of alkali metals. Hydrogen atom has one electron (ns1) in its valence shell like alkali metals. Like the alkali metals, hydrogen is monovalent.


It readily loses one electron(e-) to form a positive ion like other alkali metals.
H = H+ + e-

Combination with non-metals

Like the alkali metals, hydrogen combines readily with non-metals like halogens, oxygen, sulphur, etc. to form compounds like halides, oxides and sulphides.

Reducing agent

Hydrogen is a good reducing agent like other alkali metals. For example, hydrogen removes oxygen from oxides and acts as strong reducing agents like alkali metals.
Fe3O4 + 4H2 3Fe + 4H2O