Chemistry

Alkene (olefin): unsaturated hydrocarbons with carbon–carbon double bonds Alkene Alkenes (olefins) are hydrocarbons containing at least one carbon–carbon double bond (general formula CnH2n for simple acyclic monoenes). They are important in chemistry, industry…

Alkyne: structure, properties, reactions, and applications Alkyne Alkynes are hydrocarbons with a carbon–carbon triple bond (general formula CnH2n-2). This article explains their structure, reactivity, main reactions, common uses, and distinguish…

Allergen — substances that trigger allergic reactions Allergen An allergen is a substance that provokes an immune response in susceptible people. This article reviews common sources, how reactions develop, testing, treatment, and prevention.

Allotropes of Carbon: Forms, Structure, and Uses Allotropes of carbon Comprehensive overview of carbon allotropes — diamond, graphite, graphene, fullerenes and others — covering structures, properties, historical milestones and principal applications…

Allotropes of iron: forms, structures, and importance Allotropes of iron Overview of iron allotropes (α, β, γ, δ, ε): their crystal structures, temperature/pressure stability ranges, magnetic behavior, role in steelmaking and relevance to Earth's core.

Allotropy: distinct structural forms of chemical elements Allotropy Allotropy is the phenomenon in which a chemical element exists in two or more different structural forms (allotropes) within the same physical state, producing distinct properties…

Alloy — definition, types, production, history and common uses Alloy An alloy is a mixture of metals (and sometimes nonmetals) engineered to combine properties like strength, corrosion resistance and conductivity for specific uses.

Alnico: the iron–aluminum–nickel–cobalt alloy used for permanent magnets Alnico Alnico is an iron-based alloy of aluminum, nickel and cobalt used to make permanent magnets. Known for temperature stability and its historical role before rare-earth magnets, it r…

Alpha cleavage (α-cleavage) in organic chemistry Alpha cleavage Alpha cleavage is the breaking of the carbon–carbon bond adjacent to a functional group; important in photochemistry and mass spectrometry for producing stabilized fragments and ra…

Alum — the double sulfate salts (potassium aluminum sulfate and related compounds) Alum Alum refers to potassium aluminum sulfate and a family of double sulfate salts. This article explains composition, common types, history, practical uses, safety and how alums diffe…

Aluminium (Al): properties, occurrence, production and uses Aluminium Aluminium (Al, atomic number 13) is a lightweight, corrosion-resistant metal and the most abundant metallic element in Earth’s crust. This article covers its properties, production…

Aluminium antimonide (AlSb): properties, uses, and role in III–V semiconductors Aluminium antimonide Aluminium antimonide (AlSb) is a III–V semiconductor used mainly as a buffer and alloy component in infrared and electronic heterostructures; it helps control defects and lattice m…

Aluminium arsenide (AlAs): properties, structure, and applications Aluminium arsenide Aluminium arsenide (AlAs) is a III–V semiconductor used in heterostructures and optoelectronics. This article summarizes its structure, properties, growth methods, uses, and safety…

Aluminium chloride: properties, preparation, uses and safety Aluminium chloride Aluminium chloride (AlCl3) is a hygroscopic, strongly Lewis-acidic inorganic compound used widely as a catalyst and reagent. This article summarizes its properties, preparation, ap…

Aluminium fluoride (AlF3) Aluminium fluoride Aluminium fluoride (AlF3) is a white inorganic compound used chiefly in aluminium production as a flux and electrolyte additive; it has distinctive crystal chemistry, industrial pr…

Aluminium iodide (AlI3) Aluminium iodide Aluminium iodide denotes compounds of aluminium and iodine, most commonly aluminium triiodide (AlI3). This article explains its structure, preparation, properties, uses, reactivity…

Aluminium oxide (Al2O3) Aluminium oxide Aluminium oxide (Al2O3) is a common, hard oxide of aluminium found in ores and minerals, widely used as an abrasive, refractory material, ceramic, and intermediate in aluminium pro…

Aluminium selenide (Al2Se3) Aluminium selenide Aluminium selenide (Al2Se3) is an inorganic binary compound of aluminium and selenium. This article summarizes its composition, structure, preparation, reactivity (notably hydrolys…

Aluminium sulfate (Al2(SO4)3): properties, production and uses Aluminium sulfate Aluminium sulfate is a white crystalline inorganic salt used mainly as a water-treatment coagulant, in paper sizing and textile dyeing, and to modify soil acidity. Overview, produc…

Amalgam: mercury alloys, formation, uses, and environmental issues Amalgam An amalgam is an alloy or solution of mercury with one or more other metals. This article explains how amalgams form, common uses (dental, mining), key properties, historical conte…

Amedeo Avogadro (1776–1856) Amedeo Avogadro Italian scientist who proposed Avogadro's hypothesis linking gas volumes to particle counts; his name marks the Avogadro constant and the mole, central to chemistry and modern metr…

Americium Americium (Am, atomic number 95) is a synthetic radioactive actinide metal used in smoke detectors, neutron sources, and industrial instruments; discovered in the 1940s and named f…

Amide (chemical functional group and ion) Amide An amide is either an organic functional group R–C(=O)–NR'R'' (including peptide bonds and polyamides) or the amide ion/metal amides derived from ammonia; central to biology, mater…

Amine: structure, classification, properties and applications Amine An amine is an organic compound derived from ammonia with one or more hydrogen atoms replaced by carbon-containing groups. This article explains types, properties, reactions, histo…

Amino acid Amino acids are organic compounds that combine to form proteins; they have an amino and a carboxyl group plus a variable side chain and serve structural, metabolic, and signaling r…

Ammonia (NH3): properties, production, uses, and safety Ammonia Ammonia (NH3) is a colorless, pungent gas of nitrogen and hydrogen. This article describes its chemical nature, properties, industrial production, major uses, and safety and enviro…

Ammonium (NH4+): formation, properties, uses and environmental role Ammonium Ammonium (NH4+) is the protonated form of ammonia. This article describes its structure, common salts, chemistry, roles in biology and agriculture, environmental impacts and practi…

Ammonium carbonate: properties, uses, history, and safety Ammonium carbonate Ammonium carbonate ((NH4)2CO3) is a volatile white salt used as a leavening agent, smelling salt, and chemical reagent; it decomposes to ammonia, carbon dioxide and water and requi…

Ammonium chlorate (NH4ClO3) — properties, hazards, and uses Ammonium chlorate Ammonium chlorate (NH4ClO3) is an unstable inorganic salt combining ammonium and the chlorate ion. It is a strong oxidizer, soluble in water, prone to violent decomposition, and ha…

Ammonium chloride Ammonium chloride (NH4Cl) is a white crystalline salt formed from ammonium and chloride ions; used in metallurgy, batteries, fertilizers, medicine and laboratory chemistry.

Ammonium dichromate Ammonium dichromate ((NH4)2Cr2O7) is an orange-red inorganic oxidizer used in laboratory oxidations and classic 'volcano' demonstrations; it is highly toxic and a known carcinogen.

Ammonium nitrate Ammonium nitrate (NH4NO3) is an inorganic salt used primarily as a fertilizer and oxidizer. It is water‑soluble, thermally reactive, and regulated because of its instability and ex…

Ammonium perchlorate Ammonium perchlorate (NH4ClO4) is a white crystalline oxidizer used chiefly in solid rocket propellants; it decomposes on heating and requires careful handling due to its strong ox…

Ammonium sulfate Ammonium sulfate ((NH4)2SO4) is a white crystalline salt used mainly as a fertilizer to supply nitrogen and sulfur; it has industrial and laboratory uses and is produced by neutral…

Ammonium sulfide (NH4)2S Ammonium sulfide A laboratory reagent and industrial chemical that yields ammonia and hydrogen sulfide on decomposition; known for its strong odor and hazardous properties and used carefully in lim…

Amount of substance (chemical amount) Amount of substance Amount of substance (SI: mole) quantifies the number of specified elementary entities in a sample. This article explains its definition, relations, history, applications and key di…

Amphibole — the double-chain inosilicate mineral group Amphibole Amphiboles are a diverse group of double-chain inosilicate minerals common in igneous and metamorphic rocks, notable for prismatic crystals, variable chemistry and some asbestiform…

Anabolic steroids (anabolic–androgenic steroids) Anabolic steroid Synthetic and natural androgens that promote protein synthesis, muscle growth and male secondary sexual characteristics; used medically for hypogonadism and wasting, and misused fo…

Analytical chemistry: principles, methods, and applications Analytical chemistry Overview of analytical chemistry: scope, common techniques (chromatography, spectroscopy, mass spectrometry), qualitative vs quantitative analysis, history, sample preparation, and…

Anions: Properties, Examples, and Their Role in Ionic Compounds Anion An overview of anions—negatively charged atoms or groups that gain electrons. Explore common examples (chloride, bromide, iodide), their properties, migration under voltage, and ro…

Antacid: Uses, Types, Mechanism, Side Effects and Precautions Antacid Overview of antacids: how they neutralize stomach acid, common ingredients and formulations, typical uses, side effects, drug interactions and precautions for safe use.

Anthracite: properties, formation, uses, and global distribution Anthracite Anthracite is a high-rank, low-impurity coal valued for its high energy and low emissions. This article explains its characteristics, geological origin, uses, production centers an…

Antihydrogen — the antimatter counterpart of hydrogen Antihydrogen Antihydrogen is the antimatter form of hydrogen, made of an antiproton bound to a positron. Produced and trapped in labs, it is studied to test CPT symmetry, gravity on antimatter…

Antiknock agent Chemical additives blended into gasoline to prevent engine knocking by raising octane performance; history, mechanisms, common additives, testing, and modern regulatory and health…

Antimonide: chemistry, properties, and technological uses Antimonide Antimonide denotes compounds and the Sb3− anion containing antimony in the −3 state. This article summarizes structure, reactivity, applications (notably semiconductors), and impor…

Antimony (Sb): properties, history, and uses Antimony A concise overview of antimony (Sb): its identity, physical and chemical properties, natural occurrence, historical uses, modern applications and safety considerations.

Antimony pentachloride Antimony pentachloride (SbCl5) is a molecular antimony(V) halide and strong Lewis acid. It is corrosive, hydrolyzes readily, and is used in organic synthesis, chlorination and cata…

Antimony pentafluoride (SbF5) Antimony pentafluoride A strong, corrosive Lewis acid and fluorinating agent, SbF5 (antimony(V) fluoride) is notable for forming superacids and the hexafluoroantimonate anion used in catalysis and materi…