Oxidul

Oxide is a chemical compound that contains at least one oxygen atom bonded to another element. In English, the term covers a broad class of oxygen-containing compounds, while in Romanian the word oxidul typically refers to the same concept. Most oxides are binary compounds of oxygen with a single element, such as iron(III) oxide (Fe2O3) or silicon dioxide (SiO2).

Oxides are generally classified by the behavior of the oxide with acids and bases. Basic oxides are typically formed by metals and react with acids to form salts and water. Acid oxides are usually formed by nonmetals and react with bases to form salts and water. Amphoteric oxides can react with both acids and bases, and some oxides are considered neutral. In many solids, the bonding is largely ionic (especially metal oxides), while some nonmetal oxides exhibit covalent bonding and molecular character.

Formation and occurrence occur through oxidation processes. They form when elements react with oxygen, when metals are exposed to air, or when compounds such as carbonates and hydroxides decompose to yield oxides. Industrially, oxides are produced by roasting, calcination, or direct oxidation, and they play central roles in extracting metals and in materials processing.

Properties of oxides vary widely. Metal oxides often have high melting points and are insoluble in water, while nonmetal oxides tend to be acidic and may dissolve to form acids. Amphoteric oxides like aluminum oxide exhibit dual reactivity. Notable examples include calcium oxide used in cement, silicon dioxide in glass, titanium dioxide as a pigment, and zinc oxide in electronics and coatings.

Oxides are abundant in nature, especially in the Earth's crust, and have extensive applications in construction, manufacturing, catalysis, and technology. Safety concerns focus on inhalation of fine oxide powders and exposure to toxic metal oxides.