Chlorine (Cl) in plasma
Chlorine refuses to make a ring. Instead of a torus the whole flask fills with a pale blue-white haze that shades to lavender, dim and shapeless. That is the halogen doing what halogens do: chlorine is electronegative enough to capture free electrons out of the discharge, and without those electrons there is nothing left to sustain a tight inductive loop. What you see is the discharge losing the argument.
Pure Chlorine forms inductive plasma only at very low pressures (under 0.5 torr)
