As hydrogen has a single electron in its shell so there are two possibilities 
1. it can gain one electron to be stable so it can be placed in 1st group can also lose that electron and can be placed in 17th group of halogens
its good but i can not make out that second ppint
i just wanna tell u that hydrogen resembles both halogens as well as alkali metals
Hydrogen is a gas. But it is placed on 1A group in periodic table. That belongs to metals.
Because of its electronic configuration is 1S1 .the valency electrons is only. Because of this it was placed in 1st group. It's position is still not accurately correct as it is a gas having all metallic properties.