Chemistry

Hydrogen sulfide (H2S): properties, occurrence, uses and hazards Hydrogen sulfide Hydrogen sulfide (H2S) is a colorless, flammable, toxic gas with a distinctive rotten-egg odor. This article explains its properties, natural formation, biological roles, industria…

Hydrogen telluride (H2Te) Hydrogen telluride Hydrogen telluride (H2Te), also called tellane or hydrotelluric acid, is the volatile, highly toxic binary hydride of tellurium. It is a reducing gas used mainly in research and se…

Hydrogenation: adding hydrogen to unsaturated molecules Hydrogenation Hydrogenation is the chemical addition of hydrogen to unsaturated organic molecules. It is widely used in food, petrochemical and pharmaceutical industries and normally requires a…

Hydrolysis Hydrolysis is a chemical process where water cleaves chemical bonds, producing smaller molecules; it is central to digestion, polymer breakdown, and many industrial reactions.

Hydrometer: instrument for measuring liquid density and specific gravity Hydrometer Instrument for measuring a liquid’s specific gravity (relative density). Explains design, operating principle, common scales, uses in brewing, dairy, batteries and fuels, plus limi…

Hydron: the hydrogen ion and its isotopic forms Hydron Hydron is the IUPAC term for a positively charged hydrogen ion (H+) encompassing all isotopic nuclei — proton, deuteron, triton — and used in acid–base chemistry and related applic…

Hydroselenide (HSe−): properties, formation, and applications Hydroselenide Hydroselenide (HSe−) is the singly charged anion of hydrogen selenide. This article explains its formation, chemical behavior, salts, laboratory uses, safety considerations and dis…

Hydroxide (OH−): properties, reactions, minerals and industrial uses Hydroxide Hydroxide (OH−) is the diatomic anion of oxygen and hydrogen; it is central to base chemistry, many minerals and industrial processes including alkali manufacture, water treatment…

Hypobromite: chemistry, preparation, uses and biological role Hypobromite Hypobromite (BrO⁻) is the bromine oxyanion in oxidation state +1; an oxidizer used in disinfection and produced biologically. This entry covers its properties, preparation, uses, a…

Hypobromous acid (HBrO): properties, formation, uses and safety Hypobromous acid Hypobromous acid (HBrO) is a weak, unstable bromine oxyacid formed in water; it acts as a mild oxidant and disinfectant, disproportionates to bromate and bromide, and is generated…

Hypochlorite Hypochlorite (ClO−) is the conjugate base of hypochlorous acid: a reactive, oxidizing anion found in bleaches and disinfectants; unstable in acid and used widely for bleaching, san…

Hypochlorous acid (HOCl): properties, production, uses and precautions Hypochlorous acid Hypochlorous acid (HOCl) is a reactive chlorine-containing compound used as a disinfectant and oxidant. This article summarizes its chemistry, production methods, applications and…

Hypoiodite (IO−): properties, preparation and reactivity Hypoiodite Hypoiodite (IO−) is the monovalent oxyanion of iodine (+1). It is unstable and readily disproportionates to iodide and iodate; it appears mainly as a transient oxidant and intermed…

Hypoiodous acid (HIO) Hypoiodous acid Hypoiodous acid (HIO) is the weakest simple oxyacid of iodine, a reactive and unstable compound in which iodine is in the +1 oxidation state; it forms the hypoiodite ion (IO−) in s…

Hypomanganate (MnO4³⁻) — properties, preparation and reactivity Hypomanganate Hypomanganate is the blue manganese(V) oxoanion MnO4³⁻. It is chemically unstable, disproportionates to manganate and manganese(IV) oxide, is stabilized in strong base, and appears…

Hypophosphite (H2PO2−): properties, preparation, uses, and safety Hypophosphite Overview of the hypophosphite anion H2PO2−: structure, chemistry, common salts, preparation by disproportionation, key uses (e.g., electroless nickel) and handling hazards.

Hypophosphorous acid (H3PO2) Hypophosphorous acid Hypophosphorous acid (H3PO2) is a monoprotic phosphorus oxoacid and a versatile reducing agent; it yields hypophosphite salts and finds use in metal plating and chemical synthesis.

Ice (frozen water): properties, formation, uses, and notable facts Ice Comprehensive overview of ice — the solid form of water — covering its physical properties, formation processes, common occurrences, uses, historical notes and distinctions from ot…

Ignition Ignition is the initiation of combustion or a self‑sustaining reactive process, covering mechanisms, engine systems, safety controls, pyrotechnics, and astrophysical fusion context…

Impurity (chemistry and materials) Impurity A substance or feature present within a material that deviates from its intended purity, altering physical or chemical behavior; covers types, effects, detection, removal, and sign…

Indium — properties, occurrence, uses, and history Indium Indium (In, atomic number 49) is a soft, silvery post‑transition metal used chiefly in transparent conductive coatings, electronics and specialized alloys; overview of properties,…

Inductively Coupled Plasma Mass Spectrometry (ICP-MS) Inductively coupled plasma mass spectrometry ICP-MS is a highly sensitive analytical technique that ionizes samples in an argon plasma and measures elemental and isotopic composition at trace to ultratrace levels.

Inert gas: properties, types, history, and common uses Inert gas Gases that are largely chemically unreactive under ordinary conditions, including noble gases and molecular gases such as nitrogen. Overview of properties, types, history, applicat…

Infrared spectroscopy: principles, methods, and applications Infrared spectroscopy Overview of infrared (IR) spectroscopy: how it detects molecular vibrations, common instruments and sampling methods, major uses in chemistry and materials analysis, and its relati…

Infusion (extraction of plant compounds into a solvent) Infusion Infusion is the extraction of soluble plant compounds into a solvent such as water, oil, or alcohol by steeping; used in beverages, cooking, herbal medicine, and cosmetics.

Inner transition metals (lanthanides and actinides) Inner transition metal Inner transition metals are the f-block lanthanides and actinides. They share f-electron chemistry, distinct physical properties and important roles in technology, nuclear science,…

Inorganic (chemistry and materials) Inorganic Inorganic denotes substances and the chemistry of materials not classed as organic; it covers minerals, metals, salts, oxides, coordination complexes and related industrial and sci…

Inorganic chemistry: principles, scope, history and applications Inorganic chemistry Survey of inorganic chemistry: definition, major areas, historical development, applications in materials and catalysis, distinctions from organic chemistry, and modern interdiscip…

Inorganic compound Chemical compounds generally lacking carbon–hydrogen bonds; includes salts, oxides, metals, coordination compounds and some carbon-containing exceptions. Covers properties, classes…

Insecticide: Types, Uses, Environmental Effects and Safety Insecticide Overview of insecticides: major classes, modes of action, uses in agriculture and public health, environmental and human health concerns, resistance management, safety practices an…

Interhalogen compounds Interhalogen Interhalogens are binary compounds of two different halogens. They show distinctive stoichiometries, strong oxidizing and fluorinating behavior, varied molecular shapes and importa…

International Union of Pure and Applied Chemistry (IUPAC) International Union of Pure and Applied Chemistry IUPAC is the global authority on chemical nomenclature, terminology, standard atomic weights, and the approval of element names and symbols; it publishes internationally accepted r…

Intoxication: effects of drugs, alcohol and poisons Intoxication State of impairment after exposure to psychoactive drugs, poisons, or excessive intake of ordinary substances; covers causes, signs, clinical response, history, and legal/public he…

Invisible Ink: History, Methods, and Uses Invisible ink Invisible ink is a substance used to write messages that are normally hidden until revealed by heat, chemicals, or light; it has applications from espionage to security marking and…

Iodate (IO3−): chemistry, structure, reactions and uses Iodate Iodate (IO3−) is the oxyanion of iodine in oxidation state +5. This article explains its structure, chemical behavior, preparation, applications and safety, with typical examples l…

Iodic acid (HIO3): properties, structure, and uses Iodic acid Iodic acid (HIO3) is an oxoacid of iodine in the +5 oxidation state. This article summarizes its composition, properties, preparation, uses in chemistry and distinctions from relat…

Iodide: chemistry, biological role, and common uses Iodide Iodide (I−) is the anionic form of iodine, a mild reducing agent essential for thyroid hormones. This article covers its chemistry, biological importance, common compounds, histori…

Iodine (chemical element) Iodine Iodine is a halogen element (atomic number 53) used in nutrition, medicine, and industry; it is a dark crystalline solid that sublimes to violet vapor and forms diatomic molecules…

Iodine heptafluoride (IF7) Iodine heptafluoride Iodine heptafluoride, IF7, is a volatile interhalogen compound in which iodine attains its highest common oxidation state. It is a strong oxidizer and fluorinating agent, handled o…

Iodine monochloride (ICl): properties, preparation, uses and handling Iodine monochloride Iodine monochloride (ICl) is a red-brown interhalogen compound used as an electrophilic iodinating reagent and in iodine-value determinations; it is covalent, polar, and contains i…

Iodine pentafluoride (IF5) Iodine pentafluoride Iodine pentafluoride (IF5) is a covalent iodine fluoride used as a fluorinating reagent. It features iodine in the +5 oxidation state, a square-pyramidal geometry, and reacts vigor…

Iodine Pentoxide (I2O5): Structure, Properties, and Chemical Behavior Iodine pentoxide Overview of iodine pentoxide (I2O5): covalent structure with iodine in the +5 state, physical properties, synthesis, reactions, and applications in oxidation chemistry and iodic ac…

Iodine trichloride (ICl3): properties, structure, and uses Iodine trichloride Iodine trichloride (ICl3) is a covalent halogen compound of iodine and chlorine. It is a yellow-brown solid used as a chlorinating and oxidizing reagent and notable for its dimeric…

Iodine trifluoride (IF3) Iodine trifluoride Iodine trifluoride (IF3) is an interhalogen compound in which iodine is in the +3 oxidation state. It is a reactive, low-temperature species of interest mainly in laboratory fluori…

Ion: charged atoms and molecules — properties, formation, and applications Ion An ion is an atom or a group of atoms that carries a net electric charge. This article explains how ions form, their types, properties, roles in chemistry and physics, and common a…

Ionic bond An ionic bond is the electrostatic attraction between oppositely charged ions formed by electron transfer between atoms, producing characteristic crystalline solids with distinct p…

Ionic compound A substance made of positively and negatively charged ions held together by electrostatic attraction; characterized by crystal lattices, high melting points, solubility patterns, a…

Ionization: Formation of Ions, Mechanisms, Uses and Safety Ionization Ionization converts neutral atoms or molecules into charged ions. This article explains how ionization occurs, types and mechanisms, historical background, practical applications,…