cadmiums

Cadmiums is the term used to describe cadmium, a chemical element with symbol Cd and atomic number 48. It is a soft, bluish-white metal in group 12 of the periodic table, often associated with zinc and mercury. Cadmium occurs mainly as a byproduct of zinc refining and is extracted from zinc sulfide ores such as sphalerite. Industrial production is concentrated in a few countries, and most cadmium is refined for specialized applications.

Physically cadmium is relatively malleable and has a low melting point of about 321 degrees Celsius and a density of 8.65 g/cm3. In the environment it forms an oxide layer on exposure to air. The most common oxidation state is +2. Cadmium forms several notable compounds, including cadmium sulfide (CdS), used as a bright yellow pigment; cadmium telluride (CdTe) and cadmium selenide (CdSe) used in semiconductor and photovoltaic applications; and cadmium chloride (CdCl2), cadmium oxide (CdO), and cadmium sulfite.

Historically cadmium has been used in nickel–cadmium batteries, pigments for plastics and ceramics, coatings such as cadmium plating, and stabilizers in polyvinyl chloride. In photovoltaics, CdTe and CdS thin films have been employed. Due to toxicity, many uses have been restricted or replaced by safer alternatives, and cadmium-containing products are subject to strict handling and disposal regulations.

Health and environmental concerns: Cadmium is toxic and accumulates in the body, particularly in the kidneys, and prolonged exposure increases the risk of lung and prostate cancer; cadmium and many cadmium compounds are classified as carcinogenic to humans (IARC Group 1). Regulatory measures limit occupational exposure and cadmium discharge into the environment.

History: Cadmium was discovered in 1817 by Friedrich Stromeyer. The name derives from cadmia, an old name for zinc ore sources.