The most immediate reason is that hydrogen is a group 1 element, meaning its outer (in this case, only) shell contains just a single electron, in its s (spherically symmetric) orbital.
The electronic structure of an element greatly influences its chemical behavior, so elements in the same group tend to be chemically similar. However, hydrogen is a bit of an odd-ball as group 1 elements go.
The electronic structure of an element greatly influences its chemical behavior, so elements in the same group tend to be chemically similar. However, hydrogen is a bit of an odd-ball as group 1 elements go.