Abelsonite — a rare nickel porphyrin organic mineral Abelsonite Abelsonite is an uncommon organic mineral composed of a nickel porphyrin, noted for its purple to reddish-brown platy crystals. It is best known from the Green River Formation in U…
Absorption (physical and chemical processes) Absorption Absorption is the uptake of a substance into the bulk of a gas, liquid, or solid. This article explains mechanisms, how it differs from adsorption, common uses, and methods of meas…
Absorption spectroscopy: principles, instruments, and applications Absorption spectroscopy Overview of absorption spectroscopy: how matter absorbs light, the physical basis, instrument types, historical milestones, and common analytical and astronomical uses.
Acanthite — the low‑temperature silver sulfide mineral (Ag2S) Acanthite Acanthite is the stable low‑temperature form of silver sulfide (Ag2S). A metallic, lead‑gray ore of silver that forms in low‑temperature hydrothermal veins; notable for its monocli…
Acetamide (organic compound and rare mineral) Acetamide Acetamide (CH3CONH2) is an organic amide used in synthesis and industry; it also occurs as a rare colorless crystalline mineral, typically on shale. This article covers its propert…
Acetate (ethanoate): structure, properties, uses, and biological roles Acetate Acetate, or ethanoate, is the anion derived from acetic acid. Found in salts, esters and polymers, it plays roles in chemistry, industry and metabolism and forms common compounds l…
Acetic acid (ethanoic acid): properties, uses, and safety Acetic acid Acetic acid (CH3COOH) is a simple carboxylic acid that gives vinegar its sour character. This article summarizes its structure, physical properties, common uses, historical backgro…
Acetone (propanone): properties, production, uses, and safety Acetone Acetone (propanone) is the simplest ketone: a colorless, volatile solvent used in laboratories, industry and households. This article summarizes its properties, production, common…
Acetone peroxide (APEX): properties, hazards, and forensic significance Acetone peroxide Acetone peroxide (APEX) is a highly sensitive organic peroxide explosive. This entry summarizes its forms, hazards, forensic relevance, legal status, and safety considerations.
Acetonitrile (MeCN): Properties, Production, Uses, and Safety Acetonitrile Acetonitrile (CH3CN) is a colourless, volatile nitrile used widely as a polar aprotic solvent, in chromatography, and as an industrial intermediate. It is flammable and requires ca…
Acetyl (ethanoyl): structure, reactivity, biological roles Acetyl The acetyl group (ethanoyl) is the two‑carbon acyl fragment derived from acetic acid, central to many organic reactions and vital in biochemistry (protein acetylation, acetyl‑CoA).
Acetylcholine: the neurotransmitter of movement, autonomic function, and cognition Acetylcholine Overview of acetylcholine, a key neurotransmitter in the central and peripheral nervous systems: its synthesis, receptors, roles, historical discovery, clinical relevance, and exam…
Acetylene (C2H2): properties, production, uses and safety Acetylene Acetylene (C2H2) is the simplest alkyne: a colorless, highly flammable gas with a carbon–carbon triple bond. Used as a chemical feedstock and for oxy‑acetylene welding; requires ca…
Acetylide (C2^(2-)): structure, preparation, and uses Acetylide Acetylide (C2^(2-)), also called ethynide or dicarbide, is the dianion derived from acetylene. It forms salts and coordination compounds important in synthesis and materials chemis…
Acid — definition, properties, examples, and uses Acid Comprehensive overview of acids: definitions (Arrhenius, Brønsted–Lowry, Lewis), pH and strength, common examples, roles in nature and industry, neutralization and safety.
Acid–Base Reaction: Principles, Types, and Applications Acid–base reaction An acid–base reaction involves transfer of protons or electron pairs between acids and bases, producing salts, water in neutralization, and playing central roles in chemistry, biol…
Acryl: the acryloyl group, acrylic compounds, and their polymers Acryl A concise overview of acryl (acryloyl) functional group, its chemistry, common acrylate esters and polymers, industrial production, uses in coatings and adhesives, and important di…
Actinide (series of chemical elements) Actinide Actinides are the 15 radioactive elements from actinium to lawrencium (atomic numbers 89–103). They are f-block metals with important roles in nuclear energy, research and speciali…
Actinium (Ac), chemical element 89 Actinium Actinium (Ac, atomic number 89) is a rare, highly radioactive silvery actinide metal found in uranium ores. Notable for intense radioactivity, medical isotopes, and strict handling…
Activation energy Minimum energy barrier that reactant molecules must overcome for a chemical reaction to proceed; commonly denoted Ea and central to kinetics, catalysis, and rate predictions.
Addition reaction (organic chemistry) Addition reaction An addition reaction joins two species across a multiple bond to form a single product. Common in organic synthesis and polymer chemistry, it includes electrophilic, nucleophilic a…
Additive (chemistry and practical uses) Additive An additive is a substance introduced into a mixture or material to alter its physical, chemical, sensory, or performance properties; used across food, materials, fuels and more.
Adenine: structure, functions, and biological significance Adenine Adenine is a purine nucleobase found in DNA and RNA; it forms base pairs, contributes to energy carriers (ATP), and appears in signaling and coenzymes.
Adenosine diphosphate (ADP) Adenosine diphosphate Adenosine diphosphate (ADP) is a nucleotide that shuttles chemical energy in cells. It interconverts with ATP and plays roles in metabolism, photosynthesis, respiration and cellula…
Adhesion: how different materials stick together and why it matters Adhesion Adhesion describes the forces and processes that make dissimilar materials attach at an interface. This article explains mechanisms, factors that affect bonding, historical uses, a…
Adhesive: types, properties, history, and applications Adhesive Materials that bond surfaces together. Covers natural and synthetic adhesives, main categories and mechanisms, historic development, common uses in industry and everyday life, and…
Adsorption: Surface binding of atoms and molecules Adsorption Adsorption is the process by which atoms, molecules or particles adhere to a surface. This article explains mechanisms, types, history, examples, and practical uses across chemistr…
Aerogel: ultralight, highly insulating porous solids Aerogel Aerogel is an ultralight, highly porous solid formed by replacing a gel's liquid with gas. Known for low density, high surface area and exceptional thermal insulation, it has niche…
Aerosol: suspensions of particles or droplets in a gas Aerosol An aerosol is a cloud of fine solid particles or liquid droplets dispersed in a gas. This article explains types, formation, history, uses, and environmental and health considerati…
Aerosol spray: design, operation, uses and safety Aerosol spray An overview of aerosol sprays: how they work, main parts and propellants, common uses, brief history, and safety and environmental considerations.
Agonist (pharmacology and physiology) Agonist An agonist is a ligand that binds and activates a receptor to elicit a biological response. Agonists include full, partial, inverse and indirect types and are central to drug actio…
Akira Suzuki (chemist) — developer of the Suzuki cross‑coupling reaction Akira Suzuki (chemist) Japanese chemist Akira Suzuki (born 1930) developed the Suzuki cross‑coupling reaction and shared the 2010 Nobel Prize in Chemistry for advances in palladium‑catalyzed cross‑coupli…
Alabaster: gypsum and calcite varieties, properties and uses Alabaster Alabaster denotes two soft, workable forms of calcium—gypsum (a hydrated sulfate) and calcite (a carbonate). This article explains their composition, physical differences, history,…
Alanine Alanine (Ala, A) is a small, nonpolar α‑amino acid with a methyl side chain. L‑alanine is genetically encoded and common in proteins; D‑alanine occurs in bacterial cell walls and s…
Albumin Albumin is a group of water-soluble globular proteins found in blood serum and egg white, with roles in transport, maintaining fluid balance, laboratory use, and as an indicator of…
Alcohol (chemistry): structure, properties, production and uses Alcohol Alcohols are organic compounds with hydroxyl (–OH) group(s) on carbon. This article explains their structure, classification, properties, common uses, production and safety distinc…
Alcohol by Volume (ABV): definition, measurement, and typical ranges Alcohol by volume Alcohol by volume (ABV) is the percentage of ethanol in an alcoholic beverage measured at 20 °C. This article explains how ABV is defined, measured, typical values, regulations, an…
Alcoholic proof: measuring spirit strength and its systems Alcoholic proof Alcoholic proof is a historical and modern label indicating ethanol content in spirits. Systems vary—US proof equals twice the ABV, while other traditions used different scales. Th…
Aldehyde: Structure, Properties, Reactions and Common Uses Aldehyde Aldehydes are organic compounds with a terminal formyl group (R-CHO). This article explains their structure, typical reactions, preparation methods, examples, applications and safe…
Aldol reaction A carbon–carbon bond‑forming reaction between carbonyl compounds that produces β‑hydroxy carbonyls or α,β‑unsaturated carbonyls; widely used in synthesis and stereocontrol.
Aldrin: a persistent organochlorine insecticide Aldrin Aldrin is a chlorinated cyclodiene insecticide once used against soil pests; it is persistent, bioaccumulative and neurotoxic, and its use and production were restricted under inte…
Alexandrite: the color-change chrysoberyl gemstone Alexandrite Alexandrite is a rare variety of chrysoberyl noted for its dramatic color change under different light sources; valued in jewelry and collected for its rarity and gemological inter…
Alkali (Water-Soluble Bases): Properties, Examples, and Industrial Uses Alkali Overview of alkalis—water-soluble bases that raise pH, common examples (NaOH, KOH, Ca(OH)2, ammonia), their reactions, industrial uses and handling and safety considerations.
Alkali metals (Group 1 elements) Alkali metal Alkali metals are soft, highly reactive metals in group 1 that form +1 ions. Common members include lithium, sodium and potassium; they react vigorously with water and occur only i…
Alkaline battery: chemistry, sizes, history, and common uses Alkaline battery An overview of alkaline batteries: how they work, typical sizes and uses, historical development, safety and environmental considerations, and how they differ from other cells.
Alkaline earth metals Alkaline earth metal Group 2 elements of the periodic table — beryllium, magnesium, calcium, strontium, barium and radium — characterized by two valence electrons, common +2 ions, metallic properties a…
Alkaloid: Nitrogen‑containing natural compounds Alkaloid Alkaloids are naturally produced, basic organic compounds containing nitrogen. Found across plants, fungi, bacteria and animals, they serve ecological roles and many have important…
Alkane (saturated hydrocarbon) Alkane Alkanes are saturated hydrocarbons made of carbon and hydrogen with single C–C and C–H bonds. They occur in natural gas and petroleum and serve as fuels, solvents and chemical feed…
