Question

Why does hydrogen resemble both group $I$ and group $17$ elements ?

Answer 1

Hydrogen has electronic configuration of $1s^1$. It can accept the electron from metals to fulfill its' outer orbital like group $17$ elements. On the other hand, it can donate its' electron to form $H^{+}$ ion which is the characteristics of the group $1$ elements.

Also, it has an electronic configuration like group $1$ elements. On the other hand, it resembles group $17$ elements as it shows higher ionization enthalpy like halogens.

In this way, hydrogen resembles both group $1$ and group $17$ elements.