It's not easy to place hydrogen in the Periodic Table since it does not fit in any of the existing groups. Sometimes it is placed in the top of the group I (alkali metals) due to its relatively electropositive nature. On the other hand, it is not dificult to realize that its behaviour resembles that of halogens, accepting a second electron and becoming a mononegative ion.

In fact, the atomic structure of hydrogen (a nucleus with positive unitary electric charge and a single electron) is quite different from that of any other element, justifying its special place at the Periodic Table, not associated with any particular group.