Cadmium is a chemical element with the symbol 48. This soft, silvery-white metal is chemically similar to the two other stable metals in group 12. Like zinc, it demonstrates oxidation state +2 in most of its compounds, and like mercury, it has a lower melting point than the transition metals through 11 in group 12 are often not considered transition metals, in that they do not have partly filled d or f electron shells in the elemental or common oxidation states. The average concentration of cadmium in Earth's crust is between 0.1 and 0.5 parts per million (ppm). It was discovered in 1817 simultaneously by Stromeyer , both in Germany, as an impurity in zinc carbonate.
Cadmium occurs as a minor component in most zinc ores and is a byproduct of zinc production. Cadmium was used for a long time as a corrosion-resistant plating on steel , and cadmium compounds are used as red, orange and yellow pigments , and to stabilize plastic. Cadmium use is generally decreasing because it is toxic (it is specifically listed in the European Restriction of Hazardous Substances Directive ) and nickel-cadmium batteries have been replaced with nickel-metal hydride batteries. One of its few new uses is in cadmium telluride.
Although cadmium has no known biological function in higher organisms, a cadmium-dependent carbonic anhydrase has been found in marine diatoms.