Cadmium is a chemical element wi the seembol Cd an atomic nummer 48. This saft, bluish-white metal is chemically seemilar tae the twa ither stable metals in group 12, zinc an mercur. Lik zinc, it prefers oxidation state +2 in maist o its compoonds an lik mercur it shaws a law meltin pynt compared tae transeetion metals. Cadmium an its congeners are nae always considered transeetion metals, in that thay dae nae hae pairtly filled d or f electron shells in the elemental or common oxidation states. The average concentration o cadmium in the Yird's crust is atween 0.1 an 0.5 pairts per million (ppm). It wis discovered in 1817 simultaneously bi Stromeyer an Hermann, baith in Germany, as an impurity in zinc carbonate.