Oxids

Oxides are chemical compounds formed by oxygen with another element. They range from simple binary oxides such as iron(III) oxide (Fe2O3) and silicon dioxide (SiO2) to complex oxides with several metal cations and oxygen, such as spinels and perovskites. In oxides, the oxidation state of oxygen is typically −2, though in peroxides and superoxides oxygen forms O–O bonds and has different formal charges.

Oxides are classified as metallic or nonmetallic based on the host element, giving rise to basic oxides, acidic oxides, and amphoteric oxides; for example, CaO is basic, CO2 is acidic, and Al2O3 is amphoteric. Nonstoichiometric and oxygen-deficient oxides are common in early transition metals and in materials used for catalysis and batteries.

Occurrence and production: Oxides occur naturally as minerals, such as hematite (Fe2O3) and quartz (SiO2). They form by direct oxidation of elements, high-temperature combustion, and industrial processing. On metals, thin oxide layers often form spontaneously and protect underlying metal from further corrosion.

Uses and properties: Oxides play a central role in cement chemistry (CaO, SiO2), ceramics (Al2O3, ZrO2), pigments and alloys. Titanium dioxide (TiO2) and zinc oxide (ZnO) are common in paints and electronics. Complex oxides are key in catalysis, superconductivity, and energy storage (lithium cobalt oxide LiCoO2 in batteries).