Chemistry

Van der Waals force: weak intermolecular attractions and their roles Van der Waals force Van der Waals forces are weak, short-range noncovalent interactions between atoms and molecules — including dispersion, dipole and induced-dipole effects — important in chemistry,…

Van der Waals radius: definition, measurement, and applications Van der Waals radius A concise guide to the van der Waals radius: what it measures, how it is determined, its uses in chemistry and materials science, and how it differs from other atomic radii.

Vanadium: properties, occurrence, chemistry, uses and biological roles Vanadium Vanadium (V, atomic number 23) is a silvery transition metal used mainly to strengthen steel, with diverse oxidation states, catalytic roles, marine and biological occurrences, and…

Vapor (vapour): definition, formation, uses and distinctions Vapor Vapor (also spelled vapour) refers to the presence of a substance in the air as small liquid droplets or as a gaseous phase. This article explains formation, properties, uses, and…

Varnish: Protective Finishes for Wood and Other Surfaces Varnish Varnish is a transparent protective coating made from oils, resins and solvents. This article explains composition, types, application, history, uses, and environmental and safety…

Vitamin A: forms, functions, dietary sources, deficiency and safety Vitamin A Overview of vitamin A: chemical forms, biological roles (vision, immunity, growth), food sources and conversion, deficiency risks and public-health measures, plus safety and distin…

Volatiles (planetary science and chemistry) Volatiles Volatiles are substances with relatively low boiling or condensation temperatures that vaporize or condense easily; they shape atmospheres, ices, habitability and planetary evoluti…

Volumetric flask A laboratory flask calibrated to contain a single precise volume. Used for preparing standard solutions and accurate dilutions; features a narrow neck, a single fill mark, and a st…

VX (nerve agent) VX VX is a highly toxic organophosphate nerve agent and Schedule 1 chemical weapon. Exposure disrupts the nervous system and can be rapidly fatal; production, stockpiling and use are…

Washing: cleaning with water, soap, and detergents Washing Washing is the removal of dirt, oils and microbes using water often combined with soap or detergent. It spans personal hygiene, laundry, dishwashing and industrial cleaning and has…

Watch glass (laboratory equipment) Watch glass A shallow, slightly convex glass dish used in laboratories for holding small solids, evaporating liquids, covering beakers, observing samples and assisting in crystallization and w…

Water (molecule): properties, behavior, and importance Water (molecule) A concise guide to the water molecule (H2O): its structure, physical and chemical properties, role in the environment and biology, common uses, and notable anomalous behaviors.

Wax (organic lipids): properties, types, and common uses Wax A concise, neutral overview of wax — a class of hydrophobic organic lipids. Covers chemical nature, key properties, natural and synthetic types, historical uses, modern application…

Weak acid: properties, dissociation, examples and applications Weak acid A weak acid partially dissociates in water, establishing an equilibrium between undissociated molecules and ions. Covers characteristics, Ka/pKa, examples, buffers, polyprotic acid…

Wet chemistry (bench chemistry): techniques, equipment and applications Wet chemistry Wet chemistry, or bench chemistry, studies reactions and analyses carried out in the liquid phase using solution-based techniques such as titration, precipitation, extraction and c…

White asbestos (chrysotile): characteristics, uses, health risks and regulation White asbestos Comprehensive guide to white asbestos (chrysotile): mineral properties, historical and modern uses, how exposure causes disease, and approaches to regulation, removal and risk redu…

Whitewash (Limewash): Composition, Uses, and History Whitewash Whitewash (limewash) is a traditional mineral coating of slaked lime and chalk. This article covers its composition, common additives and colorants, application methods, historical…

Wiswesser Line Notation (WLN) Wiswesser Line Notation WLN is an early, compact linear code for describing chemical structures. Developed in the mid-20th century for punched cards, it enabled machine- and human-readable representation…

Wolff–Kishner reduction A classical organic reaction that converts aldehydes and ketones to alkanes by formation and base-induced decomposition of hydrazones; requires hydrazine, strong base, and elevated…

Woodward–Hoffmann rules A set of principles predicting stereochemical outcomes of pericyclic reactions by conserving orbital symmetry; explains when concerted pathways are allowed or forbidden under therm…

Woodward’s rules for predicting UV–Vis absorption in conjugated organic molecules Woodward's rules Empirical guidelines (Woodward–Fieser rules) for estimating the UV–Vis absorption maximum (λmax) of conjugated organic chromophores, their history, uses, and limitations.

Xanthan gum: microbial polysaccharide used as thickener and stabilizer Xanthan gum Xanthan gum is a microbial polysaccharide used as a thickener, stabilizer and binder in foods, cosmetics, pharmaceuticals and industry. It produces viscosity at low concentrations…

Xanthophylls (yellow carotenoid pigments) Xanthophyll Xanthophylls are oxygen-containing carotenoids that produce yellow colors in plants, algae and animals, contribute to photoprotection, and include compounds such as lutein and zeax…

Xenon — properties, history, compounds and applications Xenon Xenon (Xe) is a dense, colorless noble gas used in lighting, medicine, and spacecraft propulsion; notable for chemical inertness but able to form compounds under extreme conditions…

Yellowcake (uranium concentrate) Yellowcake Yellowcake is a concentrated uranium powder produced from mined ore and used as the feedstock for nuclear fuel and other industrial processes; it is not directly weapons-ready.

Yield (chemistry): types, calculation, and significance Yield (chemistry) Explanation of chemical yield: absolute, molar, fractional and percentage yield; calculation, causes of loss, reporting conventions, and practical importance in laboratory and indu…

Ytterbium Ytterbium is a soft, silvery lanthanide metal (symbol Yb, atomic number 70) used in specialty alloys, lasers and precision instruments; it occurs in rare-earth minerals and as seve…

Yttrium: properties, occurrence, applications and notable facts Yttrium Yttrium (atomic number 39) is a silvery metallic element often grouped with rare earths. This article summarizes its properties, sources, historical background, principal uses, and…

Zinc (Zn): properties, occurrence, uses, isotopes, and biological role Zinc Zinc (Zn) is a metallic chemical element (atomic number 30) widely used for galvanizing, alloys and batteries; it is an essential trace nutrient with several stable isotopes and ma…

Zinc–aluminium alloys (ZA) Zinc aluminium Zinc–aluminium (ZA) alloys are zinc-based casting alloys with aluminium additions (e.g., ZA8). They offer good bearing and wear properties, easy castability, and a range of mechani…

Zinc antimonide (ZnSb): properties, structure, uses and safety Zinc antimonide Zinc antimonide (ZnSb) is an intermetallic semiconductor formed from zinc and antimony. It appears in research and thermoelectric applications and exhibits mixed covalent–ionic bon…

Zinc arsenide (Zn3As2) — properties, preparation, uses, and safety Zinc arsenide Zinc arsenide (Zn3As2) is a gray, crystalline inorganic compound and a II–V semiconductor. It is produced from zinc and arsenic, reacts with acids to give arsine, and requires stri…

Zinc bromide (ZnBr2) Zinc bromide Zinc bromide, ZnBr2, is a hygroscopic inorganic salt used as a reagent, a heavy brine for well work, and an energy-storage electrolyte; it is corrosive and handled with care.

Zinc chloride (ZnCl2): properties, production, uses, and safety Zinc chloride Zinc chloride is a hygroscopic inorganic salt used as a Lewis acid catalyst, flux, and preservative. This article summarizes its properties, common preparations, applications, and…

Zinc fluoride (ZnF2) — properties, preparation, uses, and safety Zinc fluoride Zinc fluoride (ZnF2) is an inorganic ionic compound of Zn2+ and F−. It is a white crystalline solid with distinct structural and chemical properties, limited solubility, laboratory…

Zinc hydroxide (Zn(OH)2): properties, preparation, and uses Zinc hydroxide Zinc hydroxide, Zn(OH)2, is a sparingly soluble, amphoteric inorganic compound used in laboratory analysis and as a precursor to zinc oxide; it reacts with acids and strong bases a…

Zinc iodide (ZnI2): properties, structure, uses and safety Zinc iodide Zinc iodide (ZnI2) is a colourless, hygroscopic inorganic salt used as a laboratory reagent and Lewis acid. It is soluble in polar solvents and forms polymeric solids with bridging…

Zinc nitrate Zinc nitrate (Zn(NO3)2) is an inorganic zinc salt commonly encountered as a water-soluble, crystalline nitrate used in laboratories and industry as a reagent and precursor to zinc…

Zinc oxide (ZnO) Zinc oxide Zinc oxide (ZnO) is a white inorganic compound used as a pigment, UV absorber, semiconductor, and industrial additive; notable for amphoteric chemistry and broad commercial and med…

Zinc phosphate (Zn3(PO4)2) Zinc phosphate Zinc phosphate is an inorganic zinc salt of phosphoric acid used as an anticorrosive pigment, dental cement component, and insoluble phosphate material with characteristic ionic st…

Zinc sulfate Zinc sulfate (ZnSO4) is a water‑soluble inorganic salt used in agriculture, medicine and industry; commonly encountered as the heptahydrate crystalline form.

Zinc sulfide (ZnS) — properties, structure and uses Zinc sulfide Zinc sulfide (ZnS) is a wide‑bandgap inorganic compound found in nature as sphalerite and wurtzite. It is used as a pigment, optical material and phosphor when doped; notable for t…

Zirconium (Zr): properties, occurrence, uses, and history Zirconium Zirconium is a lustrous, corrosion-resistant transition metal (Zr, atomic number 40) used in alloys, nuclear cladding, ceramics and medical devices. Overview of properties, product…

Zyklon B: hydrogen cyanide fumigant and its historical use Zyklon B Zyklon B was a hydrogen cyanide–based fumigant developed in 1920s Germany for pest control. It became notorious for its deliberate use by Nazi Germany in extermination camps during…