Why have they quit calling bleach/lables chlorine and moved to this sodium designation now instead/hiding ?

There has been a lot of evidence that elemental chlorine is detrimental to health. Suppliers are avoiding the term % chlorine in products that do not contain elemental chlorine. It is technically more correct to state that the bleach contains sodium hypochlorite. I have checked the bottle of bleach in the laundry and it states "Active ingredient 3.5% sodium hypochlorite". This is more correct than quoting the the ingredient as chlorine. I do not know what your label says: but does it say only: "Active ingredient: X% sodium" only? That would be strange.