HYDROGEN
Even for the logic in chemistry,
Hydrogen is by far the weirdest element.
This is almost entirely due to the fact that the first electron layer,
the k layer, can host two electrons, meaning there is only one
non-stable state, which is having one electron.

What makes this special is atoms will only ever bond if it becomees more
stable, meaning reaching the noble gas configuration, with a completely filled
outer shell. For Hydrogen, this means it can either lose an electron to gain
a charge of +1, which is the more common ion, but also gain an electron and
get a charge of -1.

This means hydrogen is the only non-metal that can form kations.