Position In The Periodic Table - JEE PDF Download

What is the Position of Hydrogen in the Periodic Table?

Hydrogen, the first element in the periodic table, holds a unique position due to its atomic number of one, indicating a single electron in its atom's outermost shell. The arrangement of elements in the periodic table is determined by their electronic configurations.
Hydrogen's electronic structure is akin to that of alkali metals (ns¹) which possess one electron in their outermost shell. By accepting one electron, hydrogen can achieve the electron configuration of helium, resembling the noble gas group. This characteristic also aligns with the halogen family (ns² np⁵), which lacks one electron to complete an octet in their shells.
Considering that hydrogen exhibits traits resembling alkali metals when losing an electron to form a cation and resembling halogens when gaining an electron to become a uni-negative ion, its placement in the periodic table has posed a significant question.

Hydrogen in the Periodic Table

Moving on to the compound formation, hydrogen forms oxides, halides and sulphides resembling the alkali metals, but unlike the alkali metals it has a very high ionization enthalpy, and so it lacks metallic characteristics under normal conditions. When we look in terms of ionization enthalpy, it is found that hydrogen resembles more to halogens than alkali metals. For example, ΔiH of lithium is 520 kJ mol^-1, fluorine is 1680 kJ mol^-1 and for hydrogen, it is 1312 kJ mol^-1. It exists as a diatomic molecule like that of halogens (for example chlorine Cl₂); there is a single hydrogen bond when H2 molecule is formed.
Though hydrogen shows a lot of resemblance to halogens and alkali metals, it is very different from both. So a great thought has to be given for the position of hydrogen in the periodic table. When hydrogen loses electron, the size of its nucleus decreases and becomes almost 1.5 × 10^-3pm, which is very small as compared to the atomic sizes of normal metals and hence hydrogen ion does not exist freely in nature.