Cadmium: Definition, Facts & Uses

Instructor: Jen Look

Jen has a doctorate in chemistry and has more than a decade of experience as an educator.

Cadmium is a naturally occurring chemical element. It is used in a variety of applications including corrosion-resistant coatings, paint pigments, and rechargeable batteries. Although cadmium has been widely used in industrial applications for over 150 years, only recently was the toxicity of this element realized.

Definition of Cadmium

Cadmium is a chemical element. Elements are the building blocks for everything that has mass and takes up space. Its chemical symbol is Cd, not to be confused with the elements C (carbon) and Ca (calcium). Cadmium is element 48, meaning that each cadmium atom contains 48 protons in its nucleus. In its pure form, cadmium is a white/silver colored metal with a mass of 112.41 grams per mole. Cadmium metal is very resistant to corrosion. Cadmium also forms many compounds where it has an oxidation state of +2, including many brightly colored pigments.

Cadmium on the periodic table.

Because the highest energy electrons in cadmium are in d orbitals, cadmium and the other members of Group 12 (zinc, mercury, and coppernicum) are sometimes treated as transition metals. However, technically transition metals are atoms with partially filled d orbitals. Since Group 12's orbitals are filled completely, not partially,these elements do not fit the exact definition of transition metals. However, they do not fit neatly into any other classification, either, so it is common practice to discuss them with transition metals.

Discovery and Name

Cadmium was discovered in 1817. A number of German pharmacies were having trouble with their supply of calamine, an anti-itching medication. The chemical name for calamine is zinc oxide. The German chemist Friedrich Stromeyer examined the problematic calamine and determined that the medicine was not pure zinc oxide, but instead contained a new element. He gave the new element the name cadmium based on the Latin word cadmia, meaning calamine.

No significant amounts of pure cadmium ores have been discovered. Instead, cadmium is extracted as an impurity found in zinc ores and other minerals.

Health Effects

One of the worst known cases of cadmium poisoning is known as itai-itai or ouch-ouch disease. A large number of older women near the Kamioka mines in Japan developed sharp pain, kidney problems, and very brittle bones. The bones of victims of this disease are so fragile that a doctor snapped one woman's wrist while trying to take her pulse [1]. The first cases were reported in 1912, but it was not until 1972 that cadmium pollution was recognized as the culprit and cleanup efforts began.

Other cases of cadmium poisoning have been reported when workers inhaled cadmium dust. Even small amounts of pure cadmium can be toxic. Industrial standards now provide many safety guidelines to minimize cadmium exposure for workers.

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