Cadmium, a soft, bluish metal belonging to group IIb of the periodic table (the zinc group). Cadmium is often found associated with zinc ores such as sphalerite (zinc sulfide) and also occurs as the mineral greenockite (cadmium sulfide). It is usually produced as a byproduct when zinc, copper and lead ores are reduced. It is used in electroplating, solders, bearing alloys and in nickel-cadmium batteries. Cadmium compounds are used as phosphorescent coatings in television tubes. Cadmium and its compounds are extremely toxic, even at low concentrations. The element was discovered by F. Stromeyer in 1817 and has the chemical symbol Cd.