Chemistry

Calcium oxide (quicklime) Calcium oxide Calcium oxide (CaO), called quicklime, is a white, caustic inorganic oxide used in construction, chemical manufacture, water treatment, agriculture and industry; it reacts exotherm…

Calcium permanganate Calcium permanganate (Ca(MnO4)2) is a purple, water‑soluble inorganic oxidizer used in laboratory and industrial applications; it contains Ca2+ and the strong oxidizing permanganat…

Calcium phosphate — chemistry, natural occurrence, and uses Calcium phosphate Calcium phosphate is a family of calcium and phosphate salts (notably Ca3(PO4)2) that form minerals and biomaterials. It is important for bones, fertilizers, food additives, and in…

Calcium sulfide Calcium sulfide (CaS) is an ionic binary compound of calcium and sulfide with a rock‑salt crystal structure, high melting point, and reactivity toward water and acids; used in spec…

Californium (Cf): properties, isotopes, uses and history Californium Californium is a synthetic radioactive actinide (element 98) produced in reactors and accelerators. Notable for its neutron-emitting isotopes, it has specialized uses in industry,…

Calorimeter: instrument for measuring heat and thermal energy Calorimeter An overview of calorimeters: principles, common designs (bomb, coffee‑cup), measurement methods, historical development, practical uses, and limitations for accurate heat determina…

Cannabinoid A cannabinoid is one of a family of chemical compounds that interact with the endocannabinoid system. They occur in cannabis, in animals as endocannabinoids, or can be made synthet…

Capsaicin Capsaicin is the primary vanilloid compound in chili peppers that produces heat. Oil‑soluble and colorless, it acts on TRPV1 sensory receptors and is used in food, topical analgesi…

Carat (gold purity) Carat (purity) Explanation of carat (karat) as a measure of gold purity, conversions to percentages and millesimal fineness, common alloys and colours, history of the term, and practical uses in…

Carbocation: Structure, Stability, Reactivity, and Historical Context Carbocation A carbocation is an organic ion with a positively charged carbon atom; this article explains its structure, stabilization, formation, reactions, important examples and historical r…

Carbohydrate Carbohydrates are organic molecules composed of carbon, hydrogen and oxygen that serve as energy sources and structural components in living organisms.

Carbon — the element central to life, materials, and climate Carbon Overview of carbon: its properties, common forms (allotropes), role in chemistry and biology, major uses, and environmental and historical notes.

Carbon dioxide (CO2): properties, roles, and climate significance Carbon dioxide Carbon dioxide (CO2) is a colorless gas made of one carbon and two oxygen atoms. It participates in respiration, photosynthesis and the global carbon cycle and acts as a major gree…

Carbon disulfide (CS2) Carbon disulfide Carbon disulfide (CS2) is a volatile, linear molecular liquid used as an industrial solvent and chemical intermediate. It is flammable and toxic; modern use and handling are regula…

Carbon monoxide (CO): properties, health risks, and industrial uses Carbon monoxide Carbon monoxide (CO) is a colorless, odorless gas produced by incomplete combustion. It binds to hemoglobin, is a dangerous indoor pollutant, and is an important industrial reducin…

Carbon nanotube Hollow cylindrical molecules of carbon with exceptional strength, electrical and thermal properties; used in composites, electronics, sensors and advanced materials research.

Carbon steel: composition, properties, heat treatment and uses Carbon steel Carbon steel (plain‑carbon steel) is an iron–carbon alloy with limited other elements; properties depend on carbon content, microstructure and heat treatment, determining formabili…

Carbon tetrachloride (CCl4) Carbon tetrachloride Carbon tetrachloride is a colorless, nonflammable chlorinated solvent (CCl4) historically used in industry and refrigeration; now limited because of toxicity and ozone depletion.

Carbon‑12 (12C): stable isotope and atomic mass standard Carbon-12 Carbon-12 (12C) is the most abundant stable carbon isotope and the reference for the atomic mass unit and early definitions of the mole; vital in chemistry, mass spectrometry, and…

Carbon-14 (radiocarbon) Carbon-14 Carbon-14 is a radioactive isotope of carbon used to date formerly living material up to about 50–60 thousand years by measuring its decay to nitrogen-14.

Carbonate: the carbonate ion and its compounds Carbonate Carbonates are salts or esters that contain the carbonate ion (CO3^2−) or the carbonate functional group; they occur widely in minerals, industry, and biological systems.

Carbonated water Water into which carbon dioxide has been dissolved, producing effervescence and mild acidity; used as a beverage on its own and as the base for many soft drinks and mixers.

Carbonation: the process of dissolving carbon dioxide in liquids Carbonation Carbonation is the dissolution of carbon dioxide into a liquid, producing bubbles and a fizzy sensation. It covers methods, chemistry, common uses (soft drinks, beer, sparkling win…

Carbonyl group (C=O): structure, reactivity, and applications Carbonyl Comprehensive overview of the carbonyl functional group (C=O): bonding and electronic structure, common derivatives, typical reactions, spectroscopy, roles in biology and industry,…

Carboxylic acid Organic compounds containing a carboxyl (COOH) group; weak acids common in biology, food and industry with characteristic structure, reactions, and applications.

Carl Wilhelm Scheele — 18th‑century chemist who discovered oxygen and chlorine Carl Wilhelm Scheele German‑Swedish pharmaceutical chemist (1742–1786). Scheele identified oxygen and a chlorine‑bearing gas among many compounds; his precise apothecary work advanced analytical chemis…

Carmine (color) Carmine is a vivid deep red hue derived from a natural pigment produced by scale insects; historically prized in art, textiles, cosmetics, and food coloring.

CAS Registry Number A CAS Registry Number (CAS RN) is a unique numeric identifier assigned by the Chemical Abstracts Service to chemical substances, used worldwide for unambiguous identification in da…

Cast iron: types, properties, history and uses Cast iron Concise overview of cast iron: composition, major types and microstructures, key properties, manufacturing and heat treatments, common applications, historical context, recycling a…

Catalysis: principles, types, and applications Catalysis Catalysis is the acceleration or deceleration of chemical reactions by substances (catalysts) that provide alternative pathways and are not consumed. Overview, types, mechanisms, h…

Cation (positively charged ion) Cation A cation is an atom or molecule with a net positive charge caused by loss of electrons. This article covers formation, properties, notation, common examples, roles in chemistry and…

Cellobiose — structure, formation, and significance Cellobiose Cellobiose is a two‑unit glucose sugar produced by the partial breakdown of cellulose; it is important in studies of biomass degradation, enzymology, and industrial hydrolysis proc…

Celluloid: composition, history, uses and safety of the first thermoplastic Celluloid Celluloid is a family of nitrocellulose‑based early thermoplastics used historically in film, ivory substitutes, and small consumer goods; it is flammable and largely replaced by s…

Cellulose: structure, properties, uses, and biological role Cellulose Cellulose is the principal structural polysaccharide of plants and the most abundant organic polymer on Earth; this article describes its chemistry, occurrence, processing, applica…

Cement: composition, history, uses and environmental considerations Cement Overview of cement: what it is, how it is made, major types and uses, historical development, key properties, distinctions from concrete, and environmental impacts and alternatives…

Ceramic: Materials, Properties, History, and Applications Ceramic Ceramics are inorganic, non-metallic materials created by heating and cooling. This article reviews their composition, manufacturing, history, uses, and the distinctions between tr…

Cerium (Ce) — Properties, History, and Uses Cerium Cerium is a silvery-white lanthanide metal (atomic number 58, symbol Ce) used in catalysts, glass polishing, alloys and phosphors. This article summarizes its properties, history,…

Cermet — ceramic–metal composite materials Cermet Cermets are engineered composites combining ceramic and metallic phases to unify hardness, wear resistance, and toughness for uses from cutting tools to aerospace components.

Chalcophile: sulfur‑loving elements and sulfide minerals Chalcophile Chalcophiles are elements and compounds that preferentially bond with sulfur rather than oxygen, commonly forming sulfide minerals. Covers properties, occurrence, examples, formati…

Chalcopyrite: the primary copper ore (CuFeS2) Chalcopyrite Chalcopyrite is a copper iron sulfide mineral and the most important copper ore. This article covers its properties, occurrence, processing, uses and differences from similar miner…

Molecular chaperone (protein) Chaperone (protein) Proteins that assist the folding, assembly, disassembly and quality control of other proteins and macromolecular complexes, crucial for cellular proteostasis and preventing aggrega…

Charcoal: properties, production, uses and history Charcoal Charcoal is a porous, carbon-rich material produced by heating wood with limited oxygen. This article explains how it's made, its forms, historical role, and common uses from cooki…

Charged particle (ions, electrons and other charged particles) Charged particle A charged particle carries net electric charge. This article describes what charged particles are, how they form, their properties, interactions, detection, and their roles in chem…

Chelation: chemical binding of metal ions and its roles in science and medicine Chelation Chelation is the formation of multi-point bonds between a single metal ion and a ligand, producing stable ring-like complexes used in chemistry, medicine, industry, and environment…

Cheletropic reaction: pericyclic bond reorganization where one atom forms two bonds Cheletropic reaction A cheletropic reaction is a concerted pericyclic cycloaddition in which both new bonds form to the same atom — common in carbene additions and extrusions that release small molecul…

Chemazé — commune in Mayenne, Pays de la Loire, France Chemazé Chemazé is a small rural commune in Mayenne, Pays de la Loire, in north‑western France. It has agricultural roots, local landmarks, communal governance and a recorded population of…

Chemical bond: types, properties, models, and importance Chemical bond An accessible overview of chemical bonds: how and why atoms bind, main bond types, measures of strength and polarity, common representations, historical context, and practical sign…

Chemical burn — causes, treatment, prevention, and key distinctions Chemical burn An overview of chemical burns: what they are, common causes, first aid and medical care, prevention measures, and how acid and alkali injuries differ.