Chemistry

Disulfur decafluoride (S2F10) Disulfur decafluoride Disulfur decafluoride (S2F10) is a rare inorganic sulfur fluoride notable for its unusual bonding and high toxicity; it has no widespread commercial uses and is handled only under…

Disulfur dichloride (S2Cl2) Disulfur dichloride Disulfur dichloride (S2Cl2) is a reactive sulfur chloride used in organic synthesis and rubber vulcanization. This article summarizes its properties, structure, preparation, uses,…

Disulfur dinitride (S2N2): structure, properties and applications Disulfur dinitride Disulfur dinitride (S2N2) is a small cyclic sulfur–nitrogen compound notable for its four‑membered ring, reactivity, and role as a precursor to polymeric sulfur–nitrogen materials…

Dmitri Mendeleev: Architect of the Periodic Table Dmitri Mendeleev Russian chemist Dmitri Mendeleev (1834–1907) organized the chemical elements into a periodic system, predicted undiscovered elements and shaped modern chemistry and chemical educat…

Double bond (chemistry): structure, types, properties and significance Double bond A chemical bond in which two atoms share four electrons (bond order 2). Covers bonding (σ and π), geometry, types (alkenes, carbonyls, imines), reactivity, and notable distinctions…

Dry cell: portable electrochemical cell used in batteries Dry cell A dry cell is a sealed electrochemical cell with a non‑liquid electrolyte paste. Portable, low‑maintenance, and widely used in consumer batteries, dry cells power everyday devices…

Dry cleaning: method, solvents, process, uses and environmental issues Dry cleaning Dry cleaning is a solvent-based method for cleaning garments and textiles, using chemical solvents rather than water. This article explains the process, common solvents, uses, hist…

Dubnium (element 105) Dubnium Dubnium is a synthetic, highly radioactive transactinide element with atomic number 105. It exists only in minute, short-lived isotopes produced in particle accelerators and has no…

Duralumin — a high-strength aluminum–copper alloy Duralumin Duralumin is an age‑hardening aluminum alloy (aluminum–copper–magnesium–manganese) developed in the early 20th century, noted for its strength-to-weight ratio and historical use in…

Dye: colorants for textiles and other materials Dye An overview of dyes: what they are, how they differ from pigments, natural and synthetic sources, common classes and dyeing methods, uses, and environmental considerations.

Dynamite: invention, composition, risks, and historical role Dynamite Dynamite is a nitroglycerin‑based explosive absorbed into a porous material to reduce sensitivity. This article covers its invention, composition, development, hazards, uses and la…

Dyotropic Reaction: Pericyclic Rearrangements with Simultaneous Dual Migrations Dyotropic reaction A dyotropic reaction is a concerted pericyclic rearrangement in which two sigma bonds migrate simultaneously within a single molecule, often used to explain or enable complex organ…

Dysprosium: a rare-earth metal used in magnets, reactors, and lasers Dysprosium Dysprosium (Dy, atomic number 66) is a lanthanide metal with a silvery lustre, strong neutron absorption and notable magnetic properties. It is used in high-performance magnets, nu…

Eau de Cologne: history, composition, and uses Eau de Cologne Eau de Cologne is a light, citrus-forward type of perfume originating in Cologne, Germany. This article covers its composition, history, common uses, and how it differs from other…

Einsteinium (Es): synthetic actinide element, atomic number 99 Einsteinium Einsteinium (Es, Z=99) is a synthetic, highly radioactive actinide first identified in 1952. Produced in minute quantities, it is used for basic research on heavy-element chemistry…

Electrical cell (electrochemical cell) Electrical cell An electrical (electrochemical) cell converts chemical energy to electricity or uses electricity to drive chemical reactions; covers structure, types, operation, uses, performance…

Electrochemistry: Principles, Cells, and Practical Uses Electrochemistry Study of chemical processes that produce or consume electricity at conductive electrodes in ionic media; covers redox reactions, cells (voltaic and electrolytic), applications, and…

Electrocyclic reaction An electrocyclic reaction is a pericyclic transformation in which a pi bond and a sigma bond interconvert, with stereochemistry governed by orbital symmetry, light or heat, and tor…

Electrolysis: Principles, Methods, and Industrial Uses Electrolysis Electrolysis uses electric current to drive chemical decomposition. This article covers core principles, components, historical development, major applications, and safety and envi…

Electrolysis of Water: Principles, Reactions, Uses and Development Electrolysis of water Electrolysis of water is the process of splitting water into hydrogen and oxygen using electrical energy. This article explains the chemistry, cell components, historical context,…

Electrolyte — ionic conductors in chemistry, industry and biology Electrolyte An electrolyte is a substance that produces mobile ions and conducts electricity in a fluid or molten state; vital in batteries, electrolysis, industrial processes and physiologica…

Electron affinity Electron affinity is the energy change when a neutral gaseous atom gains an electron to form an anion; it helps explain reactivity, periodic trends, and electron-transfer behavior.

Electron configuration: arrangement, principles, and chemical significance Electron configuration Overview of how electrons occupy orbitals in atoms, the rules that govern their arrangement, connections to the periodic table, common exceptions, and chemical implications.

Electron shell: main energy levels in atoms — structure, history, and significance Electron shell An electron shell is a principal energy level in an atom where electrons are most likely found. This article covers shell structure, quantum rules, historical origin, examples, and…

Electronegativity: definition, scales, trends, and chemical significance Electronegativity Electronegativity describes an atom's tendency to attract electrons. This article explains its causes, periodic trends, major scales (Pauling, Mulliken, Allred–Rochow), practical u…

Electrophile (electron-accepting chemical species) Electrophile An electrophile is an atom or molecule that accepts an electron pair in a chemical reaction. This article describes its properties, typical examples, reaction types, theoretical co…

Electroplating: Principles, Process, and Applications Electroplating Electroplating is a technique that deposits a thin metal layer onto a conductive object using an electrical current. It improves appearance, corrosion and wear resistance, and elec…

Element: meanings in science, mathematics, technology, and culture Element Overview of the term "element," covering chemical elements, mathematical elements, classical elements, HTML elements, common distinctions, history, and uses.

Elimination reaction (organic chemistry) Elimination reaction An organic transformation in which atoms or groups are removed from a substrate to form a double or triple bond. Major mechanisms are E1, E2 and E1cB; outcome depends on substrate,…

ELISA: Enzyme-Linked Immunosorbent Assay — principles, types, and uses ELISA ELISA (enzyme‑linked immunosorbent assay) is a laboratory method for detecting and quantifying proteins, antigens, or antibodies using enzyme-labeled antibodies and colorimetric, f…

Emission spectrum An emission spectrum is the pattern of light emitted by energized atoms or molecules; it reveals characteristic wavelengths used in analysis, astronomy and diagnostics.

Emulsifier: agents that stabilize mixtures of immiscible liquids Emulsifier An emulsifier is an amphiphilic additive that helps immiscible liquids (like oil and water) form and keep stable dispersions; used in food, pharmaceuticals, cosmetics, and industry…

Emulsion: formation, types, stability and common applications Emulsion An emulsion is a mixture of two immiscible liquids in which one is dispersed as droplets in the other. This article covers types, stabilizers, formation methods, stability factors…

Enamel: Dental Tissue and Fused Glass Coatings Enamel Enamel is a hard, protective surface found in biology (tooth enamel) and in manufactured coatings (vitreous enamel). This article covers structure, formation, uses, care, history,…

Enantiomer — non-superimposable mirror-image isomers Enantiomer An enantiomer is one of a pair of stereoisomers that are mirror images but cannot be superimposed. They share many physical properties yet can behave very differently in chiral env…

Endothermic reaction A chemical process that absorbs heat from its surroundings. Covers definitions, thermodynamic sign, examples, detection, applications and distinctions from related concepts.

Enol: structure, formation, reactivity and the keto–enol relationship Enol An enol is a vinyl alcohol — an alkene bearing a hydroxyl group adjacent to a carbonyl site. This article explains structure, formation, tautomerism with carbonyls, reactivity, and…

Enthalpy: definition, meaning, measurement, and applications Enthalpy Enthalpy is a thermodynamic state function (H = U + pV) used to track heat and work exchange at constant pressure. It underpins reaction energetics, phase changes, and engineering…

Enthalpy of fusion (latent heat of melting) Enthalpy of fusion The enthalpy of fusion is the heat required to convert a solid into a liquid at constant pressure. This article explains its meaning, causes, measurement, examples, and application…

Enthalpy of Vaporization The enthalpy of vaporization is the heat required to convert a liquid into a vapor at a given pressure. This article explains its definition, measurement, temperature dependence, e…

Environmental chemistry Study of chemical processes in air, water and soil: sources, reactions, transport, fate and effects of natural and human-made substances, plus detection, modeling, remediation and…

Ephedrine — natural alkaloid, stimulant and medicinal agent Ephedrine Ephedrine is a naturally occurring alkaloid primarily from Ephedra species; it has stimulant and bronchodilator effects, medical uses, notable safety risks, and is regulated becaus…

Epoxide (oxirane): the three‑membered cyclic ether Epoxide An epoxide is a three‑membered cyclic ether (oxirane). This article explains its structure, strain and reactivity, common syntheses, ring‑opening reactions, applications and notabl…

Equilibrium constant (chemical equilibrium) Equilibrium constant A quantitative measure of the position of a chemical equilibrium. Describes the ratio of product and reactant activities at equilibrium and links to thermodynamics, temperature dep…

Erbium (Er) — properties, history, and uses Erbium Erbium (Er, atomic number 68) is a lanthanide rare-earth metal. It is used in fiber-optic amplifiers, medical lasers, glass coloring and metallurgy. This article outlines its prope…

Ergastic substance: cellular non-protoplasmic materials Ergastic substance Non‑living materials produced or stored in cells—such as crystals, oils, gums, tannins and resins—with roles in storage, defence, structure and metabolism. Occurrence and biologica…

Erlenmeyer flask (conical flask) Erlenmeyer flask Conical laboratory vessel with a flat base and narrow neck used for mixing, heating, titration, culturing and storage. Common in chemistry and biology labs; made in glass and plast…

Essential oil Concentrated volatile extracts from plants used for scent, flavor and traditional therapies; covers composition, extraction, uses, safety and common distinctions.