Question

In what respect hydrogen resembles alkali metals? How does it resemble halogen?

Answer 1

Hydrogen $(H)$ is the first and simplest element of the periodic table. It contains one electron and one proton. Therefore, its atomic number and electronic configuration are $1$ and $1{{s}^{1}}$, respectively.

Complete answer:
Hydrogen $(H)$ has an atomic number $1$. Its electronic configuration is given as $1{{s}^{1}}$. The outer electronic configuration of alkali metals is $n{{s}^{1}}$ which resembles hydrogen. Therefore, hydrogen has the ability to donate one electron and becomes a unipositive species which in turn resembles alkali metals. That’s why hydrogen forms halides, sulfides, and oxides like alkali metals. On the other hand, the outer electronic configuration of halogen is $n{{s}^{2}}n{{p}^{5}}$. It means that halogens require one electron to attain the nearest noble gas configuration. On similar lines, hydrogen has the ability to gain one electron to attain the nearest noble gas configuration and becomes a uni negative species. In this way, hydrogen resembles halogens and forms diatomic molecules i.e. ${{H}_{2}}$, $C{{l}_{2}}$, $B{{r}_{2}}$ and so on. Moreover, hydrogen forms hydrides and covalent compounds with other elements as halogens form.

Additional Information: In contrast to the resemblance between alkali metals and hydrogen, hydrogen doesn’t possess a metallic character and has high ionization enthalpy. In terms of ionization enthalpy, hydrogen resembles more with halogens.

Note:
It is important to note that electron configuration of Hydrogen $(H)$ is $1{{s}^{1}}$. Therefore, hydrogen has the ability to donate one electron and becomes a uni-positive species which in turn resembles alkali metals. While hydrogen has the ability to gain one electron and becomes uni-negative species which in turn resemble halogens.