Chemistry

Antimony pentoxide (Sb2O5) Antimony pentoxide Antimony pentoxide, Sb2O5, is a inorganic antimony(V) oxide used in catalysts, flame-retardant systems, and glass; it is a white to yellowish powder containing Sb in the +5 oxidati…

Antimony tetroxide (Sb2O4): properties, structure and uses Antimony tetroxide Antimony tetroxide (Sb2O4) is a mixed‑valence inorganic oxide of antimony. It contains both Sb(III) and Sb(V), appears as a crystalline oxide, and is used in ceramics, catalysts, a…

Antimony tribromide (SbBr3): properties, structure, uses, and safety Antimony tribromide Antimony tribromide (SbBr3) is an inorganic antimony(III) halide used as a laboratory reagent and Lewis acid; this article covers its composition, structure, reactions, application…

Antimony trichloride (SbCl3): properties, reactions, and uses Antimony trichloride Antimony trichloride (SbCl3) is a covalent antimony(III) chloride used as a Lewis acid in synthesis; it hydrolyzes in moist air, forms oxychlorides, and requires careful handling d…

Antimony trifluoride (SbF3) Antimony trifluoride Antimony trifluoride, SbF3, is an inorganic fluoride of antimony in the +3 oxidation state used as a fluorinating reagent in organic and inorganic chemistry; known historically as…

Antimony triiodide (SbI3): properties, preparation, uses, and safety Antimony triiodide Antimony triiodide (SbI3) is a molecular inorganic compound of antimony in the +3 oxidation state and iodide. This article covers its properties, structure, preparation, applicatio…

Antimony trioxide (antimony(III) oxide) Antimony trioxide Antimony trioxide (Sb2O3) is the most common oxide of antimony. A white crystalline powder, it occurs in nature, is made from antimony ores, and is used as a flame‑retardant synerg…

Antimony trisulfide (Sb2S3) Antimony trisulfide Antimony trisulfide (Sb2S3) is an inorganic sulfide found in the mineral stibnite. It has historical uses as kohl, technical uses in pyrotechnics and pigments, and modern interest…

Antioxidant Molecules that slow or prevent oxidation by neutralizing free radicals. Present in foods and produced in the body, antioxidants play roles in nutrition, physiology, food preservati…

Antoine Lavoisier: the chemist who founded modern chemistry Antoine Lavoisier French chemist and nobleman (1743–1794) whose experiments established the law of conservation of mass, named oxygen and hydrogen, helped displace phlogiston theory and shaped chemi…

Apatite (phosphate mineral group) Apatite Apatite is a family of calcium phosphate minerals containing hydroxyl, fluoride or chloride; it forms the mineral basis of bone and tooth enamel and is an important source of phosp…

Aqua regia: composition, chemistry, history and applications Aqua regia Aqua regia is a highly corrosive, oxidizing mixture of concentrated nitric and hydrochloric acids (1:3) used to dissolve gold and platinum in refining, analysis and etching; handle…

Aqueous solution A homogeneous mixture in which water is the solvent. Covers definition, components, physical and chemical properties, notation (aq), common examples, types of solutes, and practica…

Argon (Ar) — inert noble gas: properties, history and common uses Argon Argon is a colorless, odorless noble gas (Ar, atomic number 18). Inert and abundant in air, it has industrial uses from welding to insulating glass and roles in scientific instrume…

Armstrong's mixture A highly sensitive explosive mixture of potassium chlorate, phosphorus and sulfur, historically used in small priming charges and novelty noisemakers; extremely hazardous and restr…

Aromatic hydrocarbon (arene) Aromatic hydrocarbon Arenes are hydrocarbons with conjugated cyclic π systems (benzene-like rings). They are chemically stable, widely used in industry, and include simple benzene to complex polycyclic…

Arsenate (AsO4 3−): chemistry, biology, and environmental significance Arsenate Arsenate is the As(V) oxyanion AsO4 3−, the conjugate base of arsenic acid. It occurs in minerals and water, resembles phosphate chemically, and is toxic because it disrupts cellul…

Arsenic Arsenic is a metalloid chemical element (As, atomic number 33) known for its varied chemistry, industrial uses (including gallium arsenide), and significant toxicity and environmen…

Arsenic acid (H3AsO4) Arsenic acid Arsenic acid, H3AsO4, is a triprotic oxyacid of arsenic in the +5 oxidation state. It forms arsenate salts, is used in some industrial processes, and is toxic and environmentally r…

Arsenic pentafluoride (AsF5) Arsenic pentafluoride Arsenic pentafluoride (AsF5) is a molecular inorganic fluoride of arsenic in the +5 oxidation state; a reactive Lewis acid used in fluorine chemistry and as a precursor to hexafluo…

Arsenic pentoxide (As2O5) Arsenic pentoxide Arsenic pentoxide, As2O5, is the pentavalent oxide of arsenic. A white, hygroscopic oxidizing solid, it hydrolyzes to arsenic acid, is highly toxic and corrosive, and is used mainl…

Arsenic Sulfides — Minerals, Chemical Properties, Uses and Environmental Risks Arsenic sulfide Overview of arsenic sulfides—minerals like orpiment and realgar, their chemical and physical properties, technological uses such as chalcogenide glasses and pigments, plus health,…

Arsenic tribromide (AsBr3): properties, preparation and safety Arsenic tribromide Arsenic tribromide (AsBr3) is an inorganic molecular compound of arsenic and bromine. This article covers its structure, preparation, reactivity, uses in synthesis, and important s…

Arsenic trichloride (arsenic(III) chloride) Arsenic trichloride Arsenic trichloride (AsCl3) is a volatile inorganic liquid used as a chemical reagent and precursor to organoarsenic compounds; it is corrosive and highly toxic and hydrolyzes in w…

Arsenic trifluoride (arsenic(III) fluoride) Arsenic trifluoride Arsenic trifluoride (AsF3) is a covalent arsenic halide used in specialized synthesis. It is a volatile, toxic, colorless liquid with a trigonal pyramidal molecular structure and d…

Arsenic triiodide (AsI3): properties, preparation, and precautions Arsenic triiodide Arsenic triiodide (AsI3) is a covalent arsenic(III) halide used mainly in research. This article covers its structure, preparation, reactivity, uses, and safety considerations.

Arsenic trioxide (As2O3): properties, uses, history and safety Arsenic trioxide Arsenic trioxide (As2O3), also called white arsenic, is an industrial and medicinal compound containing arsenic in the +3 oxidation state. It is highly toxic and environmentally si…

Arsenic trisulfide (orpiment) Arsenic trisulfide Arsenic trisulfide (As2S3), known as orpiment, is a yellow arsenic sulfide mineral and compound used historically as a pigment and today in chalcogenide glasses; it is chemically t…

Arsenide (As3−): chemistry, properties, reactions and uses Arsenide Arsenide refers to compounds or the As3− anion in which arsenic has a −3 formal oxidation state. The term covers ionic salts, intermetallic phases and semiconductor compounds with…

Arsenite: chemical forms, properties, toxicity and environmental role Arsenite Arsenite refers to arsenic(III) oxyanions and related salts. This article explains chemical forms, structure, toxicity, environmental behavior, uses, and how arsenite differs from…

Arsenous acid (arsenious acid) — properties, occurrence, and significance Arsenous acid Arsenous acid (As(OH)3), also called arsenious acid, is the aqueous form of trivalent arsenic. It is a weak, toxic acid that forms arsenite species and is important in environmenta…

Artificial sweetener (sugar substitute) Artificial sweetener A non-sugar substance used to impart sweetness without the calories of sucrose; includes types, uses, history, regulation, and health considerations.

Ascorbic acid (vitamin C): properties, biological role, uses and history Ascorbic acid Ascorbic acid (vitamin C) is a water‑soluble antioxidant and essential nutrient. This article covers its chemistry, biological functions, dietary sources, production, uses as a foo…

Asphalt (bitumen): composition, uses, history and environmental issues Asphalt Asphalt, also called bitumen, is a dark, viscous petroleum product used chiefly in road paving, roofing and waterproofing. This article covers composition, types, history, uses, an…

Astatine (Element 85): Properties, Isotopes, History and Uses Astatine Astatine is a rare, highly radioactive halogen (atomic number 85). All its isotopes are short-lived; its chemistry is poorly characterized but resembles iodine while showing metall…

Atmospheric chemistry: composition, processes, and environmental impacts Atmospheric chemistry Scientific study of the chemical composition and reactions in Earth's and other planets' atmospheres, their sources, effects on air quality and climate, and methods used to observe…

Atom: the basic unit of matter Atom An atom is the smallest unit of a chemical element that retains its properties. This article explains atomic structure, size, isotopes, bonding, historical development, and practic…

Atomic mass and isotopic mass: definition, units, and relation to mass number Atomic mass Defines atomic and isotopic mass, explains units (u and SI), shows how mass number and nucleons relate, and covers isotopes, relative atomic mass and how averages differ from singl…

Atomic number (Z) Atomic number The atomic number is the count of protons in an atom's nucleus. It defines the chemical element, determines the number of electrons in a neutral atom, and orders the periodic table…

Atomic radius Overview of atomic radius: definitions, how it is measured, periodic trends, historical notes, and why atomic size matters in chemistry and materials science.

Atomic theory: development, structure, and applications Atomic theory A concise account of atomic theory: its modern formulation, subatomic structure, historical development, key models, applications across sciences, and limitations in extreme states…

Auger electron spectroscopy: surface-sensitive elemental analysis Auger electron spectroscopy Auger electron spectroscopy (AES) is a surface-sensitive analytical technique that identifies elements and probes their chemical environment by measuring energies of emitted Auger…

Austenite — the gamma phase of iron and its role in steels Austenite Austenite is the face-centered cubic (γ) phase of iron that forms at high temperature and in many alloyed steels; it governs carbon solubility, heat-treatment behavior and key mech…

Avogadro constant The Avogadro constant (N_A) is the fixed number of elementary entities in one mole: exactly 6.02214076×10^23 mol⁻¹. It connects atomic-scale counts to laboratory-scale amounts and…

Avogadro's law: equal volumes of gases contain equal numbers of molecules Avogadro's law Avogadro's law states that equal volumes of gases, at the same temperature and pressure, contain the same number of molecules. It underpins the mole concept and gas stoichiometry.

Azide (N3−): properties, reactivity, uses and safety Azide Azide (N3−) is a linear, resonance-stabilized anion found in inorganic and organic azides. It is reactive and useful in synthesis and airbags but forms toxic and often shock-sensit…

Babbitt metal: alloy for low‑friction bearings Babbitt metal Babbitt metal (white metal) is a soft, low‑friction bearing alloy, typically tin‑ or lead‑based with copper and antimony. It forms a conforming lining that retains lubricant and ca…

Bain-marie (water bath) Bain-marie A bain-marie, or water bath, is a device for gentle, uniform heating used in laboratories, industry, and kitchens to maintain precise, steady temperatures.