Hydrogen is in its own group on the periodic table, Group 1, also known as the hydrogen group. This is because hydrogen has unique properties that set it apart from the other elements in the periodic table.

While hydrogen has one valence electron like the alkali metals in Group 1, its chemical behavior is quite different. For instance, hydrogen can form covalent bonds with non-metals, whereas alkali metals exclusively form ionic bonds. Additionally, hydrogen has a very low atomic mass and a high ionization energy, which distinguish it from other elements in Group 1.

Therefore, hydrogen is placed in its own group to acknowledge its unique characteristics and to reflect the fact that it does not fit neatly into any other group.