Question

How many hydrogen atoms does chlorine need to be stable​

Answer 1

A chlorine atom is not stable. Chlorine has 7 electrons in its outer shell and needs 8 electrons for it to be full, thus it is not stable.

Answer 2

Answer:

With seven electrons in its outermost orbit--one electron short of a "stable eight"-- the element chlorine exists in nature as a diatomic molecule. This arrangement allows two chlorine atoms to share their outermost orbit electrons, achieving stability, compared to the single atom.