Chemistry

Salt (chemistry): structure, properties, and uses Salt An overview of salts in chemistry: ionic structure, physical and chemical properties, common types (like sodium chloride), formation, uses, and practical distinctions.

Samarium (chemical element) Samarium Samarium is a silvery rare-earth metal (atomic number 62) used in high-performance magnets, nuclear applications, and geochronology. It belongs to the lanthanide series and has sev…

Sapphire — mineral, varieties, history and uses Sapphire Sapphire is the gem-quality variety of corundum (aluminium oxide) valued for its range of colors, hardness, historical symbolism and uses in jewelry and industry.

Sarin Sarin is a highly toxic organophosphate nerve agent developed in the 1930s and classified as a chemical weapon; exposure causes rapid cholinergic crisis and respiratory failure and…

Saturated fat: definition, properties, dietary sources, and health context Saturated fat Saturated fat: chemical definition, physical properties, common food sources, culinary uses, and current understanding of effects on blood lipids and health.

Saturation (chemistry) Saturation in chemistry describes when a substance or system is 'filled' — common uses include saturated solutions, saturated vapors, saturated hydrocarbons, and ligand saturation.

Scandium: properties, occurrence, uses and history Scandium Scandium (Sc, atomic number 21) is a silvery transition metal found in trace amounts worldwide; valued for aluminium alloys, specialty lighting and niche high-tech uses despite lim…

Seaborgium (element 106) Seaborgium Seaborgium (Sg, Z=106) is a synthetic, radioactive transition metal in group 6. Known only from laboratory production, it has short-lived isotopes and no commercial uses; its chemi…

Selectivity Selectivity is the property of a system, process, or measurement to preferentially respond to, produce, or admit some inputs over others; used in chemistry, pharmacology, electroni…

Selenate (SeO4^2−) Selenate Selenate is the tetrahedral oxyanion of selenium in its highest common oxidation state. This article summarizes its structure, chemistry, uses, environmental behaviour and safety c…

Selenic acid (H2SeO4) Selenic acid Selenic acid (H2SeO4) is a powerful selenium oxoacid and oxidizing agent that yields selenate salts; it is used in laboratory synthesis and must be handled as a corrosive, toxic su…

Selenide (the Se2− ion and its compounds) Selenide Overview of the selenide ion (Se2−), its chemistry, common compounds, natural occurrence, technological uses, and safety considerations.

Selenite (SeO3²⁻): the selenite ion and its chemistry Selenite Overview of the selenite oxyanion (SeO3²⁻): structure, formation, common salts, chemical behavior, uses, and distinctions from related selenium species.

Selenium — properties, uses, biological role and history Selenium Selenium (Se, Z=34) is a chalcogen element with semiconductor and photoconductive properties, essential in trace amounts for life, used in glass, electronics and solar technology;…

Selenium dioxide (SeO2) Selenium dioxide Selenium dioxide (SeO2) is the +4 oxide of selenium. A volatile, water‑soluble oxidizing agent, it is used in organic synthesis and glassmaking but is toxic and must be handled wit…

Selenium disulfide Selenium disulfide (SeS2) is a chalcogenide compound used mainly as a topical antifungal agent in medicated shampoos; it is a polymeric selenium–sulfur material with distinct chemi…

Selenium hexafluoride (SeF6) Selenium hexafluoride Selenium hexafluoride is a volatile inorganic compound of selenium in the +6 oxidation state. It is a colorless molecular gas with an octahedral structure, limited uses and signifi…

Selenium monochloride (Se2Cl2): properties, structure, synthesis, uses Selenium monochloride Selenium monochloride (Se2Cl2) is a covalent selenium halide with an Se–Se bond. This article covers its structure, preparation, chemical behavior, applications in synthesis, and s…

Selenium tetrachloride (SeCl4) Selenium tetrachloride Selenium tetrachloride (SeCl4) is a selenium(IV) halide used in synthesis and research. It is a volatile, moisture-sensitive chlorinating and selenylating reagent that hydrolyzes t…

Selenium tetrafluoride (SeF4) Selenium tetrafluoride Selenium tetrafluoride, SeF4, is a volatile selenium(IV) fluoride used as a fluorinating reagent and studied for its molecular structure, reactivity with water and donors, and safe…

Selenium trioxide (selenium(VI) oxide), SeO3 Selenium trioxide Selenium trioxide (SeO3) is the anhydride of selenic acid and a strong inorganic oxidizer. It hydrolyzes to selenic acid, is mainly a laboratory reagent, and requires careful handl…

Selenous acid (H2SeO3): properties, preparation, uses, and safety Selenous acid Selenous acid (H2SeO3) is an inorganic oxoacid of selenium(IV). This article covers its structure, preparation, common applications, reactivity and safety considerations.

Semiconductor: materials, physics, and applications Semiconductor An accessible overview of semiconductors: definition, underlying physical principles, common materials, device types, fabrication, history and major applications.

Semisolid: properties, examples, and applications Semisolid A semisolid is a material intermediate between a solid and a liquid. This article explains its defining properties, typical examples, microstructure, applications, and how it diffe…

Semtex — pliable plastic explosive Semtex Semtex is a moldable plastic explosive originally manufactured in Czechoslovakia. It is valued for stability and power in demolition but notorious for use in criminal attacks, prom…

Separating Funnel Laboratory glassware used to separate immiscible liquid phases (liquid–liquid extraction). Describes design, operation, uses, common problems (emulsions), safety and alternatives.

Shampoo: cleansing products for hair and body Shampoo Shampoo is a formulated cleanser for hair and scalp, designed to remove oils, dirt and styling residues. Types include daily, clarifying, conditioning, medicated and solid bars; se…

Shielding effect (electronic screening) in atoms Shielding effect The shielding effect is the reduction in attraction between outer electrons and the nucleus due to intervening electrons; it shapes atomic size, ionization energy, and periodic tre…

Side chain (chemistry) Side chain A side chain is a group of atoms attached to the main backbone of a molecule. This article explains types, notation, chemical effects, roles in polymers and proteins, naming, and p…

Sigma bond (σ bond): formation, properties, and examples Sigma bond A sigma (σ) bond is the primary covalent bond formed by end-to-end overlap of atomic orbitals. This article explains how σ bonds form, their symmetry, relation to π bonds, common e…

Sigmatropic reaction A sigmatropic reaction is a concerted pericyclic rearrangement in which a sigma bond migrates across a conjugated pi system, reorganizing connectivity within a single molecule and…

Silicate: structure, types, occurrence and uses Silicate Silicates are minerals and compounds built from silicon centered anions (commonly SiO4 tetrahedra) that form chains, sheets or frameworks; they dominate Earth’s crust and have wide…

Silicon: properties, occurrence, uses, and role in technology Silicon An overview of silicon (Si): its properties as a metalloid and semiconductor, natural occurrence in silica and silicates, industrial production, major applications in electronics,…

Silicon Dioxide (Silica): Properties, Natural Forms, Uses and Health Effects Silicon dioxide Comprehensive overview of silicon dioxide (silica): chemical nature, common mineral forms, industrial uses, historical context, and health and safety considerations.

Silicone (silicones): chemistry, properties, history and uses Silicone Silicones are synthetic polymers built on siloxane units. This article explains their chemistry, common forms, properties, history, major applications, safety and how they differ f…

Silver (chemical element) Silver Silver (Ag), atomic number 47, is a lustrous transition metal prized for its conductivity, reflectivity and malleability; used historically for coinage and jewelry and today in ele…

Silver bromide (AgBr): properties, structure, and photographic use Silver bromide Silver bromide (AgBr) is a light-sensitive inorganic salt of silver and bromide. It forms pale crystalline solids, used historically in photography and still studied for photochemi…

Silver chloride (AgCl) Silver chloride Silver chloride is an inorganic salt of silver and chloride ions, notable for its low solubility, photosensitivity, use in analytical chemistry and as a component of reference elec…

Silver fluoride Silver fluoride denotes binary compounds of silver and fluorine, most commonly silver(I) fluoride (AgF) and silver(II) fluoride (AgF2); they differ in oxidation state, properties,…

Silver iodate (AgIO3) Silver iodate Silver iodate, AgIO3, is an ionic inorganic salt made of Ag+ and IO3−. It is a sparingly soluble oxidizing solid used in laboratory chemistry and analytical reactions; handle as an…

Silver iodide (AgI) Silver iodide Silver iodide, AgI, is a yellow, sparingly soluble silver salt used in cloud seeding, solid-state ionics and photographic science; it forms several crystal phases and is photosensi…

Silver nitrate Silver nitrate (AgNO3) is a colorless, water‑soluble salt of silver(I) used in photography, medicine, analytical chemistry and organic synthesis. It is light‑sensitive and an oxidi…

Silver oxide Overview of silver oxide compounds, their properties, preparation, uses (batteries, catalysts, antimicrobials), and distinctions among common forms (Ag2O, AgO).

Silver oxide battery Silver oxide batteries are small primary cells using a silver oxide cathode and zinc anode in an alkaline electrolyte. They provide a stable 1.55 V output and are used in watches,…

Silver(I,III) oxide A mixed-valence silver oxide containing silver in more than one oxidation state; noted for its unique structure, reactivity, and use as a cathode material in some primary batteries…

Silver(I) carbonate Silver(I) carbonate (Ag2CO3) is an inorganic silver salt of carbonate. A pale yellow, sparingly soluble solid, it is used as a source of Ag+ and as a reagent in synthesis and analy…

Silver(I) fluoride Silver(I) fluoride (AgF) is a simple silver salt of fluoride: a water-soluble, ionic compound used as a fluoride source in chemistry, with distinct properties and safety considerat…

Silver(I) oxide (Ag2O) Silver(I) oxide Silver(I) oxide (Ag2O) is a dark brown to black inorganic solid used in button cells, as a mild oxidant in synthesis and as a precursor to ammoniacal silver reagents; it reacts wit…