Editing Period 5 element (section)

===Cadmium===
{{main|Cadmium}}
'''Cadmium''' is a [[chemical element]] with the symbol '''Cd''' and [[atomic number]] 48. This soft, bluish-white metal is chemically similar to the two other stable metals in [[group 12 element|group 12]], [[zinc]] and [[mercury (element)|mercury]]. Like zinc, it prefers [[oxidation state]] +2 in most of its compounds and like mercury it shows a low melting point compared to [[transition metal]]s. Cadmium and its [[Congener (chemistry)|congeners]] 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 the Earth's crust is between 0.1 and 0.5 parts per million (ppm). It was discovered in 1817 simultaneously by [[Friedrich Stromeyer|Stromeyer]] and [[Karl Samuel Leberecht Hermann|Hermann]], both in Germany, as an impurity in [[zinc carbonate]].

Cadmium occurs as a minor component in most zinc ores and therefore is a byproduct of zinc production. It was used for a long time as a [[pigment]] and for corrosion resistant plating on [[steel]] while cadmium compounds were used to stabilize [[plastic]]. With the exception of its use in [[nickel–cadmium battery|nickel–cadmium batteries]] and [[cadmium telluride]] [[solar panel]]s, the use of cadmium is generally decreasing. These declines have been due to competing technologies, cadmium's [[toxicity]] in certain forms and concentration and resulting regulations.<ref name="ReferenceA">{{cite book|chapter = Cadmium|title = Kirk-Othmer Encyclopedia of Chemical Technology|edition = 4th|place=New York|publisher = John Wiley & Sons|year=1994|volume= 5}}</ref>