Chemistry

Nickel(II) carbonate (NiCO3) Nickel(II) carbonate Nickel(II) carbonate (NiCO3) is a green, water‑insoluble nickel salt and carbonate mineral precursor used in ceramics, catalysts and chemical synthesis. It decomposes on heating to…

Nickel(II) chloride (NiCl2) — properties, uses and safety Nickel(II) chloride Nickel(II) chloride (NiCl2) is a common nickel salt that forms hydrates, is soluble in water, and is used in electroplating, catalysis and synthesis. It is corrosive, allergenic, a…

Nickel(II) hydroxide Nickel(II) hydroxide (Ni(OH)2) is a green, sparingly soluble inorganic compound used as an electrode material in rechargeable batteries and as a precursor for catalysts and nickel…

Nickel(II) nitrate (nickelous nitrate) Nickel(II) nitrate Nickel(II) nitrate, Ni(NO3)2, is an inorganic nickel salt typically encountered as hydrated green crystals. It is water soluble, acts as an oxidizer and laboratory precursor to nic…

Nickel(II) oxide (NiO) Nickel(II) oxide Nickel(II) oxide (NiO) is a green to black inorganic compound of nickel in the +2 oxidation state, used in ceramics, catalysts, electrochemical cells and as a precursor to other ni…

Nickel(II) sulfate An inorganic nickel salt (NiSO4) commonly found as a green hexahydrate. Used in plating, battery materials and synthesis; toxic and regulated, with several hydrate forms and indust…

Nickel(III) oxide (Ni2O3): overview, properties, preparation and uses Nickel(III) oxide Nickel(III) oxide, often written Ni2O3, is a less-common nickel oxide containing Ni(III). Its composition and structure are not well established; Ni(III) species are important in b…

Nicotine: properties, sources, effects, history, and uses Nicotine Nicotine is an alkaloid found primarily in tobacco; it acts on nicotinic receptors, produces stimulant and addictive effects, and is central to tobacco dependence, cessation therap…

Nihonium (Nh): synthetic element 113 Nihonium Nihonium (Nh, atomic number 113) is a short-lived, synthetic element named for Japan. It is a group 13 transactinide produced in particle accelerators with no commercial uses and o…

Niobium (Nb): properties, history, occurrence, and uses Niobium Niobium (Nb, atomic number 41) is a ductile, corrosion-resistant transition metal used to strengthen steels, form superconducting alloys, and make corrosion-resistant parts; it occ…

Nitrate (NO3−): structure, uses, production and environmental effects Nitrate Nitrate (NO3−) is a common polyatomic ion found in salts, fertilizers, food preservatives and explosives; it has a resonance-stabilized trigonal planar structure and important envi…

Nitric acid (HNO3): properties, production, uses and safety Nitric acid Nitric acid is a strong, corrosive mineral acid (HNO3) used in industry, laboratory chemistry and explosives. This article covers its properties, manufacture, historical names and…

Nitric oxide (NO): properties, roles, and applications Nitric oxide Nitric oxide (NO) is a small, reactive gaseous molecule and free radical with roles in chemistry, physiology, and the environment; used industrially and medically, and distinct fro…

Nitride (compounds of nitrogen with less electronegative elements) Nitride Nitride: inorganic compounds in which nitrogen combines with less electronegative elements. Covers types, bonding, preparation, applications (semiconductors, ceramics), naming conv…

Nitrile (organic functional group and related compounds) Nitrile Nitriles are organic compounds containing a carbon–nitrogen triple bond (–C≡N). They occur in solvents and polymers, arise in synthesis, and vary widely in properties and toxicity.

Nitrite (NO2−): properties, occurrence, uses and safety Nitrite Nitrite is the inorganic anion NO2− with nitrogen in oxidation state +3. This article summarizes its structure, chemistry, common salts, industrial and food uses, environmental rol…

Nitro compound Organic molecules that contain the nitro functional group (-NO2); structure, bonding, typical reactions, preparation methods, uses, and safety considerations.

Nitrocellulose (cellulose nitrate, guncotton) Nitrocellulose Nitrocellulose is a nitrate ester of cellulose known for rapid combustion and use as propellant, film base, lacquer and plastic; it has important historical uses and significant sa…

Nitrogen (chemical element) Nitrogen Nitrogen is a colorless, odorless diatomic nonmetal (symbol N, atomic number 7) that makes up about 78% of Earth's atmosphere and is essential for life, agriculture and many indust…

Nitrogen dioxide (NO2) — properties, sources, and impacts Nitrogen dioxide Nitrogen dioxide (NO2) is a reddish-brown, toxic gas formed by combustion. It is an oxidant in the atmosphere, contributes to smog and acid rain, and is an important industrial int…

Nitrogen fixation Conversion of inert atmospheric nitrogen (N₂) into reactive forms like ammonia by biological, atmospheric, and industrial processes; essential to the nitrogen cycle, agriculture, a…

Nitrogen oxide (nitrogen oxides): overview, properties, and impacts Nitrogen oxide Collective term for chemical compounds of nitrogen and oxygen (e.g., NO, NO2, N2O) important in combustion chemistry, atmospheric pollution, climate forcing and biological signalin…

Nitrogen trichloride (trichloramine) Nitrogen trichloride Nitrogen trichloride (NCl3), commonly called trichloramine, is a volatile, unstable chlorine–nitrogen compound notable for its pungent odor, explosiveness in concentrated form and…

Nitrogen triiodide: properties, hazards, and history Nitrogen triiodide Nitrogen triiodide is an extremely sensitive contact explosive, usually encountered as an ammonia adduct. This article summarizes its properties, hazards, formation, and historical…

Nitroglycerin (glyceryl trinitrate): properties, history, uses, and safety Nitroglycerin Nitroglycerin (glyceryl trinitrate) is a colorless oily liquid used as a powerful explosive and as a medical vasodilator. This article outlines its chemistry, history, applications…

Nitrous acid (HNO2) — properties, preparation, reactions, and uses Nitrous acid Nitrous acid (HNO2) is a weak, unstable acid that exists mainly in aqueous solution; important in organic nitrosation, diazotization, and atmospheric nitrogen oxide chemistry.

Nitrous oxide (N2O) Nitrous oxide Nitrous oxide is a colorless gas (N2O) used as an anesthetic, propellant and oxidizer. It is also a long-lived, potent greenhouse gas produced naturally and by human activity.

NMR spectroscopy: principles, instruments, and applications NMR spectroscopy Overview of nuclear magnetic resonance (NMR) spectroscopy: physical basis, common experiments, interpretation, instrumentation, history, and principal applications in chemistry and…

Nobelium (element No, atomic number 102) Nobelium Nobelium is a synthetic, radioactive actinide element (No, Z=102). It has no stable isotopes, is produced in particle accelerators, and is studied for nuclear and chemical research…

Noble gases Noble gas A concise, neutral overview of the noble (group 18) elements: their properties, history, uses, and notable distinctions, with examples and safety notes.

Noble gas compound A compound that contains one or more atoms of a Group 18 (noble) element. Once considered inert, several noble gases form stable or metastable compounds under special conditions.

Noble metal A class of metals resistant to oxidation and corrosion; includes gold, silver, platinum group metals and others used in jewelry, catalysis, electronics and specialized industrial r…

Nonmetal (chemical element) Nonmetal Nonmetals are chemical elements that lack metallic properties: poor electrical and thermal conductivity, absence of metallic luster, and a tendency to gain electrons; they include…

Novichok — Soviet-era family of nerve agents Novichok Novichok is a name for a family of nerve agents developed in the Soviet Union from the 1970s. These organophosphate compounds are often binary, highly toxic, and implicated in seve…

Nuclear chemistry Study of atomic nuclei and radioactive processes: principles, techniques, history, applications in energy, medicine, dating and industry, and how it differs from nuclear physics an…

Nuclear reaction Overview of nuclear reactions: types, mechanisms, occurrences, applications, and how they differ from chemical reactions.

Nucleophile (chemistry): definition, properties and reactivity Nucleophile A nucleophile is an electron-pair donor that attacks electron-poor centers. This article explains what nucleophiles are, how they behave, factors that influence them, and their rol…

Nucleophilic substitution: mechanisms, factors, and applications Nucleophilic substitution Nucleophilic substitution reactions involve replacement of a group on a molecule by a nucleophile. This article explains the main mechanisms (SN1, SN2), influencing factors, varian…

O2 — diatomic oxygen, telecom brand, arenas, and other meanings O2 O2 most commonly denotes molecular oxygen (O2). It also refers to a European telecom brand and sponsored arenas, an automotive oxygen sensor, a U.S. military pay grade (O‑2), and o…

Ochre (Ocher): natural earth pigment and its uses Ochre Ochre is a natural earth pigment of hydrated iron oxides, producing yellow to red-brown tones. Used since prehistory in art, decoration, cosmetics and building materials.

Octane (C8H18): chemistry, isomers, fuels, and octane rating Octane Octane, a C8H18 alkane, is a colorless flammable hydrocarbon and a key component of gasoline. This article explains its structure, isomers, role in fuels, octane ratings, uses, and…

Octane rating: what it means for gasoline, engines, and fuel performance Octane rating Octane rating measures a fuel's resistance to knock (auto-ignition). This article explains how ratings are determined, the difference between RON/MON/AKI, historical additives, and…

Octene Octene is an eight‑carbon alkene (C8H16) that exists in several isomeric forms. It is used industrially as an alpha‑olefin feedstock and intermediate in plastics, detergents and lu…

Octet rule A chemical guideline stating that many atoms attain stability with eight electrons in their valence shell; useful for predicting simple bonding but limited by many exceptions.

Odor: chemical basis, perception, history and uses Odor Odor (smell) is the perception of volatile chemical compounds by olfactory systems. This article explains what odors are, how they are detected, their history, practical uses, and…

Oganesson (Og): the synthetic element with atomic number 118 Oganesson Oganesson (Og) is the heaviest known element, a short-lived synthetic member of group 18 (atomic number 118). It has no practical uses and is studied for its extraordinary, relativ…

Oleum (fuming sulfuric acid) Oleum Oleum is a solution of sulfur trioxide in sulfuric acid—called fuming sulfuric acid—used industrially to make concentrated sulfuric acid and as a strong sulfonating agent; it is hi…

Organic chemistry: principles, structures, reactions and applications Organic chemistry Survey of organic chemistry: carbon-based molecules, structures and bonding, major reaction types, history, analytical methods, and roles in biology, industry, and medicine.