As with group 1 metals, halogens will also
undergo the process that is easier.
While for group 1 metals it was easier for
them to lose 1 electrons instead of gaining 7, for halogens, it is
easier for them to gain 1 electrons instead of losing 7!!
Not only that remember that the electrons
in the different shells in an atom are attracted by the protons in the
nucleus and the strength with which they are attracted is different
for electrons in different shells.
–The closer the shell is to the nucleus,
the more strongly the electrons in it are attracted by the nucleus and therefore
the more reactive the halogen.