 Cadmium is a chemical element with symbol Cd and atomic number 48 . This soft , bluish @-@ white metal is chemically similar to the two other stable metals in group 12 , zinc and mercury . Like zinc , it demonstrates oxidation state + 2 in most of its compounds , and like mercury , it has a lower melting point than other transition metals . Cadmium and its <unk> are not always 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 and Hermann , both in Germany , as an impurity in zinc carbonate . 
