Question

What is unusual about hydrogen? Why is it placed separately in periodic table ?​

Answer 1

Dear Student ,

Hydrogen has a lone s-electron. Thus it can lose an electron to achieve a stable configuration like alkali metals and hence can be placed in group 1 (alkali metals). However, it can also gain an electron to achieve a noble gas arrangement and hence it can behave similar to a group 17 (halogen family) elements. Also, like group 14 elements, its valence shell is half full.

Thus its configuration resembles the configuration of three different groups. This is why it is placed separately in the periodic table.
Regards