calcium telluride is a chemical element with the symbol Ca. It is an essential component of the human body and has a range of natural and prepared compounds.
Common crystalline forms of calcium are carbonate (CaCO3), sulfate (CaSO4), nitrate (CaNO3), phosphate (Ca3(PO4)2) and oxalate. Other important minerals are gypsum, limestone and fluorite.
In the ground, calcium is found in sand, salts and clay. When heated, it can form a variety of substances including quicklime (CaO), which is used to make white paint and cleaning powder. It is also used to form slaked lime, which is an inexpensive base material in the chemical industry.
Biologically, calcium is found in bones, teeth and shells. It is a major part of the immune system, helping protect the body against disease.
Chemically, calcium is a highly reactive metal. It is a reducing agent for thorium, uranium and zirconium. It is also a deoxidizer, desulfurizer and decarburizer for several ferrous and nonferrous alloys. It is a “getter” in vacuum tubes and serves as an alloying agent for aluminum, beryllium, copper, lead and magnesium.
Calcium is a highly toxic metal, the oxidation state being the most important factor in toxicity. It can cause respiratory depression and circulatory collapse after occupational exposure.
Tellurium is also a toxic metal with a range of oxidation states. The most dangerous oxidation states are the tellurites (TeO3)2- and tellurates (TeO4)2-, which have a high charge per unit.
Besides being a toxic metal, tellurium is a rare and costly commodity, so it is often reacted to create valuable products. For example, the atomic energy division of GE produces calcium tellurides to be used in its X-ray spectrometers for monitoring cancer.