chemistry Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science that covers the Chemical element, elements that make up matter to the chemical compound, compounds made of atoms, molecules and ions ...

, an onium ion is a

cation An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by convent ...

formally obtained by the

protonation In chemistry, protonation (or hydronation) is the adding of a proton (or hydron, or hydrogen cation), (H+) to an atom, molecule, or ion, forming a conjugate acid. (The complementary process, when a proton is removed from a Brønsted–Lowry acid, ...

of mononuclear parent

hydride In chemistry, a hydride is formally the anion of hydrogen( H−). The term is applied loosely. At one extreme, all compounds containing covalently bound H atoms are called hydrides: water (H2O) is a hydride of oxygen, ammonia is a hydride of ...

of a

pnictogen A pnictogen ( or ; from grc, πνῑ́γω "to choke" and -gen, "generator") is any of the chemical elements in group 15 of the periodic table. Group 15 is also known as the nitrogen group or nitrogen family. Group 15 consists of the el ...

(group 15 of the

periodic table The periodic table, also known as the periodic table of the (chemical) elements, is a rows and columns arrangement of the chemical elements. It is widely used in chemistry, physics, and other sciences, and is generally seen as an icon of ch ...

chalcogen The chalcogens (ore forming) ( ) are the chemical elements in group 16 of the periodic table. This group is also known as the oxygen family. Group 16 consists of the elements oxygen (O), sulfur (S), selenium (Se), tellurium (Te), and the radioact ...

(group 16), or

halogen The halogens () are a group in the periodic table consisting of five or six chemically related elements: fluorine (F), chlorine (Cl), bromine (Br), iodine (I), astatine (At), and tennessine (Ts). In the modern IUPAC nomenclature, this group is ...

(group 17). The oldest-known onium ion, and the namesake for the class, is

ammonium The ammonium cation is a positively-charged polyatomic ion with the chemical formula or . It is formed by the protonation of ammonia (). Ammonium is also a general name for positively charged or protonated substituted amines and quaternary a ...

, , the protonated derivative of

ammonia Ammonia is an inorganic compound of nitrogen and hydrogen with the formula . A stable binary hydride, and the simplest pnictogen hydride, ammonia is a colourless gas with a distinct pungent smell. Biologically, it is a common nitrogenous was ...

, . The name onium is also used for cations that would result from the substitution of hydrogen atoms in those ions by other groups, such as organic radicals, or halogens; such as

tetraphenylphosphonium Tetraphenylphosphonium chloride is the chemical compound with the formula (C6H5)4PCl, abbreviated Ph4PCl or PPh4Cl. Tetraphenylphosphonium and especially tetraphenylarsonium salts were formerly of interest in gravimetric analysis of perchlorate an ...

, . The substituent groups may be divalent or trivalent, yielding ions such as

iminium In organic chemistry, an iminium cation is a polyatomic ion with the general structure . They are common in synthetic chemistry and biology. Structure Iminium cations adopt alkene-like geometries. The central C=N unit is nearly coplanar with al ...

and

nitrilium A nitrilium ion is a nitrile that has been protonated, CNHsup>+, or alkylated, CNR′sup>+. Synthesis Nitriles are only weakly basic and are poor nucleophiles, but they will attack very reactive electrophiles such as carbocations. Nitrilium ...

. A simple onium ion has a charge of +1. A larger ion that has two onium ion subgroups is called a double onium ion, and has a charge of +2. A triple onium ion has a charge of +3, and so on. Compounds of an onium cation and some other

anion An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by convent ...

are known as onium compounds or onium salts. Onium ions and onium compounds are inversely

analog Analog or analogue may refer to: Computing and electronics * Analog signal, in which information is encoded in a continuous variable ** Analog device, an apparatus that operates on analog signals *** Analog electronics, circuits which use analog ...

ous to ions and

ate complex In chemistry, an ate complex is a salt formed by the reaction of a Lewis acid with a Lewis base whereby the central atom (from the Lewis acid) increases its valence and gains a negative formal charge. (In this definition, the meaning of valence i ...

es: *

Lewis bases A Lewis acid (named for the American physical chemist Gilbert N. Lewis) is a chemical species that contains an empty orbital which is capable of accepting an electron pair from a Lewis base to form a Lewis adduct. A Lewis base, then, is any s ...

form onium ions when the central atom gains one more bond and becomes a positive

. *Lewis acids form ions when the central atom gains one more bond and becomes a negative

Simple onium cations (hydrides with no substitutions)

Group 13 The Group 13 network ( pl, Trzynastka, Yiddish: ''דאָס דרײַצענטל'') was a Jewish Nazi collaborationist organization in the Warsaw Ghetto during the German occupation of Poland in World War II. The rise and fall of the Group ...
(boron group) onium cations

boronium In chemistry, a boranylium ion is an inorganic cation with the chemical formula , where R represents a non-specific substituent. Being electron-deficient, boranylium ions form adducts with Lewis bases. Boranylium ions have historical names that ...

cation, (protonated

borane Trihydridoboron, also known as borane or borine, is an unstable and highly reactive molecule with the chemical formula . The preparation of borane carbonyl, BH3(CO), played an important role in exploring the chemistry of boranes, as it indicated ...

) **further boronium cations, (protonated

boranes Boranes is the name given to compounds with the formula BxHy and related anions. Many such boranes are known. Most common are those with 1 to 12 boron atoms. Although they have few practical applications, the boranes exhibit structures and bond ...

)

Group 14 The carbon group is a group (periodic table), periodic table group consisting of carbon (C), silicon (Si), germanium (Ge), tin (Sn), lead (Pb), and flerovium (Fl). It lies within the p-block. In modern International Union of Pure and Applied Chem ...
(carbon group) onium cations

carbonium ion In chemistry, a carbonium ion is any cation that has a pentavalent carbon atom. The name carbonium may also be used for the simplest member of the class, properly called methanium (), where the five valences are filled with hydrogen atoms. The ...

s (protonated

hydrocarbon In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. Hydrocarbons are examples of group 14 hydrides. Hydrocarbons are generally colourless and hydrophobic, and their odors are usually weak or ex ...

s) have a pentavalent carbon atom with a +1 charge. **alkanium cations, (protonated

alkane In organic chemistry, an alkane, or paraffin (a historical trivial name that also has other meanings), is an acyclic saturated hydrocarbon. In other words, an alkane consists of hydrogen and carbon atoms arranged in a tree structure in which ...

s) ***

methanium In chemistry, methanium is a complex positive ion with formula []+, namely a molecule with one carbon atom covalent bond, bonded to three hydrogen atoms and one hydrogen molecule, bearing a +1 electric charge. It is a superacid and one of the ...

, (protonated

methane Methane ( , ) is a chemical compound with the chemical formula (one carbon atom bonded to four hydrogen atoms). It is a group-14 hydride, the simplest alkane, and the main constituent of natural gas. The relative abundance of methane on Eart ...

) (Sometimes called

carbonium In chemistry, a carbonium ion is any cation that has a pentavalent carbon atom. The name carbonium may also be used for the simplest member of the class, properly called methanium (), where the five valences are filled with hydrogen atoms. The nex ...

, because it is the simplest member of that class, but that use is deprecated because of multiple definitions. Sometimes called methonium, but methonium also has multiple definitions. Abundant in outer space.) ***

ethanium In chemistry, ethanium or protonated ethane is a highly reactive positive ion with formula . It can be described as a molecule of ethane () with one extra proton (hydrogen nucleus), that gives it a +1 electric charge. Ethanium is one of the s ...

, (protonated

ethane Ethane ( , ) is an organic chemical compound with chemical formula . At standard temperature and pressure, ethane is a colorless, odorless gas. Like many hydrocarbons, ethane is isolated on an industrial scale from natural gas and as a petr ...

) *** propanium, (

propane Propane () is a three-carbon alkane with the molecular formula . It is a gas at standard temperature and pressure, but compressible to a transportable liquid. A by-product of natural gas processing and petroleum refining, it is commonly used a ...

protonated on an unspecified carbon) **** propylium, or propan-1-ylium (propane protonated on an end carbon) **** propan-2-ylium (propane protonated on the middle carbon) *** butanium, (

butane Butane () or ''n''-butane is an alkane with the formula C4H10. Butane is a gas at room temperature and atmospheric pressure. Butane is a highly flammable, colorless, easily liquefied gas that quickly vaporizes at room temperature. The name but ...

protonated on an unspecified carbon) **** ''n''-butanium ( ''n''-butane protonated on an unspecified carbon) ***** ''n''-butylium, or ''n''-butan-1-ylium (''n''-butane protonated on an end carbon) ***** ''n''-butan-2-ylium (n-butane protonated on a middle carbon) **** isobutanium (

isobutane Isobutane, also known as ''i''-butane, 2-methylpropane or methylpropane, is a chemical compound with molecular formula HC(CH3)3. It is an isomer of butane. Isobutane is a colourless, odourless gas. It is the simplest alkane with a tertiary carbon a ...

protonated on an unspecified carbon) ***** isobutylium, or isobutan-1-ylium (isobutane protonated on an end carbon) ***** isobutan-2-ylium (isobutane protonated on the middle carbon) ***

octonium In chemistry, a carbonium ion is any cation that has a pentavalent carbon atom. The name carbonium may also be used for the simplest member of the class, properly called methanium (), where the five valences are filled with hydrogen atoms. The ...

or octanium, (protonated

octane Octane is a hydrocarbon and an alkane with the chemical formula , and the condensed structural formula . Octane has many structural isomers that differ by the amount and location of branching in the carbon chain. One of these isomers, 2,2,4-Tri ...

) * silanium (sometimes silonium), (protonated

silane Silane is an inorganic compound with chemical formula, . It is a colourless, pyrophoric, toxic gas with a sharp, repulsive smell, somewhat similar to that of acetic acid. Silane is of practical interest as a precursor to elemental silicon. Sila ...

) (should not be called siliconiumRC-82. Cations
Queen Mary University of London) ** disilanium, (protonated

disilane Disilane is a chemical compound with chemical formula Si2H6 that was identified in 1902 by Henri Moissan and Samuel Smiles (1877–1953). Moissan and Smiles reported disilane as being among the products formed by the action of dilute acids on meta ...

) **further silanium cations, (protonated

silanes Silanes refers to diverse kinds of charge-neutral silicon compounds with the formula . The R substituents can any combination of organic or inorganic groups. Most silanes contain Si-C bonds, and are discussed under organosilicon compounds. Examp ...

) * germonium, (protonated

germane Germane is the chemical compound with the formula Ge H4, and the germanium analogue of methane. It is the simplest germanium hydride and one of the most useful compounds of germanium. Like the related compounds silane and methane, germane is te ...

) * stannonium, (protonated ) (not protonated

stannane Stannane or tin hydride is an inorganic compound with the chemical formula . It is a colourless gas and the tin analogue of methane. Stannane can be prepared by the reaction of and . : Stannane decomposes slowly at room temperature to give ...

) * plumbonium, (protonated )

Group 15 A pnictogen ( or ; from grc, πνῑ́γω "to choke" and -gen, "generator") is any of the chemical elements in group 15 of the periodic table. Group 15 is also known as the nitrogen group or nitrogen family. Group 15 consists of the ...
(pnictogen) onium cations

(

IUPAC The International Union of Pure and Applied Chemistry (IUPAC ) is an international federation of National Adhering Organizations working for the advancement of the chemical sciences, especially by developing nomenclature and terminology. It is ...

name azanium), (protonated

(IUPAC name azane)) *

phosphonium In polyatomic cations with the chemical formula (where R is a hydrogen or an alkyl, aryl, or halide group). These cations have tetrahedral structures. The salts are generally colorless or take the color of the anions. Types of phosphonium ...

, (protonated

phosphine Phosphine (IUPAC name: phosphane) is a colorless, flammable, highly toxic compound with the chemical formula , classed as a pnictogen hydride. Pure phosphine is odorless, but technical grade samples have a highly unpleasant odor like rotting ...

) *

arsonium The arsonium cation is a positively charged polyatomic ion with the chemical formula . An arsonium salt is a salt containing either the arsonium () cation, such as arsonium bromide () and arsonium iodide (), which can be synthesized by reacting ...

, (protonated

arsine Arsine (IUPAC name: arsane) is an inorganic compound with the formula As H3. This flammable, pyrophoric, and highly toxic pnictogen hydride gas is one of the simplest compounds of arsenic. Despite its lethality, it finds some applications in ...

) * stibonium, (protonated stibine) * bismuthonium, (protonated

bismuthine Bismuthine (IUPAC name: bismuthane) is the chemical compound with the formula BiH3. As the heaviest analogue of ammonia (a pnictogen hydride), BiH3 is unstable, decomposing to bismuth metal well below 0 °C. This compound adopts the expected ...

)

Group 16 The chalcogens (ore forming) ( ) are the chemical elements in group 16 of the periodic table. This group is also known as the oxygen family. Group 16 consists of the elements oxygen (O), sulfur (S), selenium (Se), tellurium (Te), and the radioa ...
(chalcogen) onium cations

* oxonium, (protonated

water Water (chemical formula ) is an inorganic, transparent, tasteless, odorless, and nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all known living organisms (in which it acts as a ...

(IUPAC name oxidane). Oxonium is better known as

hydronium In chemistry, hydronium (hydroxonium in traditional British English) is the common name for the aqueous cation , the type of oxonium ion produced by protonation of water. It is often viewed as the positive ion present when an Arrhenius acid is d ...

, though hydronium implies a solvated or hydrated proton. It may also be called

hydroxonium In chemistry, hydronium (hydroxonium in traditional British English) is the common name for the aqueous cation , the type of oxonium ion produced by protonation of water. It is often viewed as the positive ion present when an Arrhenius acid is di ...

.) *

sulfonium In organic chemistry, a sulfonium ion, also known as sulphonium ion or sulfanium ion, is a positively-charged ion (a " cation") featuring three organic substituents attached to sulfur. These organosulfur compounds have the formula . Together wi ...

, (protonated

hydrogen sulfide Hydrogen sulfide is a chemical compound with the formula . It is a colorless chalcogen-hydride gas, and is poisonous, corrosive, and flammable, with trace amounts in ambient atmosphere having a characteristic foul odor of rotten eggs. The unde ...

) * selenonium, (protonated

hydrogen selenide Hydrogen selenide is an inorganic compound with the formula H2Se. This hydrogen chalcogenide is the simplest and most commonly encountered hydride of selenium. H2Se is a colorless, flammable gas under standard conditions. It is the most toxic sel ...

) * telluronium, (protonated

hydrogen telluride Hydrogen telluride is the inorganic compound with the formula hydrogen, H2telluride (chemistry), Te. A hydrogen chalcogenide and the simplest hydride of tellurium, it is a colorless gas. Although unstable in ambient air, the gas can exist at very ...

)

Group 17 The halogens () are a group (periodic table), group in the periodic table consisting of five or six chemically related chemical element, elements: fluorine (F), chlorine (Cl), bromine (Br), iodine (I), astatine (At), and tennessine (Ts). In the ...
(halogen) onium cations,
halonium ion A halonium ion is any onium ion containing a halogen atom carrying a positive charge. This cation has the general structure where X is any halogen and no restrictions on R, this structure can be cyclic or an open chain molecular structure. Halo ...
s, H₂X⁺ (protonated
hydrogen halide In chemistry, hydrogen halides (hydrohalic acids when in the aqueous phase) are diatomic, inorganic compounds that function as Arrhenius acids. The formula is HX where X is one of the halogens: fluorine, chlorine, bromine, iodine, or astatine. A ...
s)

fluoronium The fluoronium ion is an inorganic cation with the chemical formula . It is one of the cations found in fluoroantimonic acid. The structure of the salt with the anion, has been determined. The fluoronium ion is isoelectronic with the water ...

, (protonated

hydrogen fluoride Hydrogen fluoride (fluorane) is an inorganic compound with the chemical formula . This colorless gas or liquid is the principal industrial source of fluorine, often as an aqueous solution called hydrofluoric acid. It is an important feedstock i ...

) *

chloronium A halonium ion is any onium ion containing a halogen atom carrying a positive charge. This cation has the general structure where X is any halogen and no restrictions on R, this structure can be cyclic or an open chain molecular structure. Halon ...

, (protonated

hydrogen chloride The compound hydrogen chloride has the chemical formula and as such is a hydrogen halide. At room temperature, it is a colourless gas, which forms white fumes of hydrochloric acid upon contact with atmospheric water vapor. Hydrogen chloride ga ...

) *

bromonium A halonium ion is any onium ion containing a halogen atom carrying a positive charge. This cation has the general structure where X is any halogen and no restrictions on R, this structure can be cyclic or an open chain molecular structure. Haloni ...

, (protonated

hydrogen bromide Hydrogen bromide is the inorganic compound with the formula . It is a hydrogen halide consisting of hydrogen and bromine. A colorless gas, it dissolves in water, forming hydrobromic acid, which is saturated at 68.85% HBr by weight at room temper ...

) *

iodonium A halonium ion is any onium ion containing a halogen atom carrying a positive charge. This cation has the general structure where X is any halogen and no restrictions on R, this structure can be cyclic or an open chain molecular structure. Halon ...

, (protonated

hydrogen iodide Hydrogen iodide () is a diatomic molecule and hydrogen halide. Aqueous solutions of HI are known as hydroiodic acid or hydriodic acid, a strong acid. Hydrogen iodide and hydroiodic acid are, however, different in that the former is a gas under sta ...

)

Pseudohalogen Pseudohalogens are polyatomic analogues of halogens, whose chemistry, resembling that of the true halogens, allows them to substitute for halogens in several classes of chemical compounds. Pseudohalogens occur in pseudohalogen molecules, inorganic ...
onium cations

* aminodiazonium, (protonated

hydrogen azide Hydrazoic acid, also known as hydrogen azide or azoimide, This also contains a detailed description of the contemporaneous production process. is a compound with the chemical formula . It is a colorless, volatile, and explosive liquid at room tem ...

) *methylidyneammonium/hydrocyanonium, , isomers HC≡NH⁺ and N≡CH (protonated

hydrogen cyanide Hydrogen cyanide, sometimes called prussic acid, is a chemical compound with the formula HCN and structure . It is a colorless, extremely poisonous, and flammable liquid that boils slightly above room temperature, at . HCN is produced on an ...

)

Group 18 The noble gases (historically also the inert gases; sometimes referred to as aerogens) make up a class of chemical elements with similar properties; under standard conditions, they are all odorless, colorless, monatomic gases with very low chemi ...
(noble gas) onium cations

hydrohelium The helium hydride ion or hydridohelium(1+) ion or helonium is a cation (positively charged ion) with chemical formula HeH+. It consists of a helium atom bonded to a hydrogen atom, with one electron removed. It can also be viewed as protonated ...

helonium The helium hydride ion or hydridohelium(1+) ion or helonium is a cation (positively charged ion) with chemical formula HeH+. It consists of a helium atom bonded to a hydrogen atom, with one electron removed. It can also be viewed as protonated ...

, better known as

helium hydride ion The helium hydride ion or hydridohelium(1+) ion or helonium is a cation (positively charged ion) with chemical formula HeH+. It consists of a helium atom bonded to a hydrogen atom, with one electron removed. It can also be viewed as protonated h ...

, HeH⁺ (protonated

helium Helium (from el, ἥλιος, helios, lit=sun) is a chemical element with the symbol He and atomic number 2. It is a colorless, odorless, tasteless, non-toxic, inert, monatomic gas and the first in the noble gas group in the periodic table. ...

) *

neonium Neon compounds are chemical compounds containing the element neon (Ne) with other molecules or elements from the periodic table. Compounds of the noble gas neon were believed not to exist, but there are now known to be molecular ions containing ...

, NeH⁺ (protonated

neon Neon is a chemical element with the symbol Ne and atomic number 10. It is a noble gas. Neon is a colorless, odorless, inert monatomic gas under standard conditions, with about two-thirds the density of air. It was discovered (along with krypton ...

) *

argonium Argonium (also called the argon hydride cation, the hydridoargon(1+) ion, or protonated argon; chemical formula ArH+) is a cation combining a proton and an argon atom. It can be made in an electric discharge, and was the first noble gas molecula ...

, ArH⁺ (protonated

argon Argon is a chemical element with the symbol Ar and atomic number 18. It is in group 18 of the periodic table and is a noble gas. Argon is the third-most abundant gas in Earth's atmosphere, at 0.934% (9340 ppmv). It is more than twice as abu ...

) * kryptonium, KrH⁺ (protonated

krypton Krypton (from grc, κρυπτός, translit=kryptos 'the hidden one') is a chemical element with the symbol Kr and atomic number 36. It is a colorless, odorless, tasteless noble gas that occurs in trace amounts in the atmosphere and is often ...

) * xenonium, XeH⁺ (protonated

xenon Xenon is a chemical element with the symbol Xe and atomic number 54. It is a dense, colorless, odorless noble gas found in Earth's atmosphere in trace amounts. Although generally unreactive, it can undergo a few chemical reactions such as the ...

) *trifluoroxenonium, ( is neutral.)

Hydrogen onium cation

*hydrogenonium, better known as

trihydrogen cation The trihydrogen cation or protonated molecular hydrogen is a cation (positive ion) with formula , consisting of three hydrogen nuclei ( protons) sharing two electrons. The trihydrogen cation is one of the most abundant ions in the universe. It ...

, H (protonated molecular or diatomic

hydrogen Hydrogen is the chemical element with the symbol H and atomic number 1. Hydrogen is the lightest element. At standard conditions hydrogen is a gas of diatomic molecules having the formula . It is colorless, odorless, tasteless, non-toxic, an ...

), found in ionized hydrogen and interstellar space

Onium cations with monovalent substitutions

*primary ammonium cations, RH₃N⁺ or RNH (protonated primary

amine In chemistry, amines (, ) are compounds and functional groups that contain a basic nitrogen atom with a lone pair. Amines are formally derivatives of ammonia (), wherein one or more hydrogen atoms have been replaced by a substituen ...

s) ** hydroxylammonium, NH₃OH⁺ (protonated

hydroxylamine Hydroxylamine is an inorganic compound with the formula . The material is a white crystalline, hygroscopic compound.Greenwood and Earnshaw. ''Chemistry of the Elements.'' 2nd Edition. Reed Educational and Professional Publishing Ltd. pp. 431–43 ...

) ** methylammonium, CH₃NH (protonated

methylamine Methylamine is an organic compound with a formula of . This colorless gas is a derivative of ammonia, but with one hydrogen atom being replaced by a methyl group. It is the simplest primary amine. Methylamine is sold as a solution in methanol, ...

) ** ethylammonium, C₂H₅NH (protonated ethylamine) **

hydrazinium Hydrazinium is the cation with the formula . This cation has a methylamine-like structure (). It can be derived from hydrazine by protonation (treatment with a strong acid). Hydrazinium is a weak acid with p''K''a = 8.1. Salts of hydrazinium ar ...

, or diazanium, NH₂NH (protonated

hydrazine Hydrazine is an inorganic compound with the chemical formula . It is a simple pnictogen hydride, and is a colourless flammable liquid with an ammonia-like odour. Hydrazine is highly toxic unless handled in solution as, for example, hydrazine ...

, a.k.a. diazane) **anilinium (a.k.a. phenylammonium), (protonated

aniline Aniline is an organic compound with the formula C6 H5 NH2. Consisting of a phenyl group attached to an amino group, aniline is the simplest aromatic amine In organic chemistry, an aromatic amine is an organic compound consisting of an aroma ...

, a.k.a. phenylamine, aminobenzene) *secondary ammonium cations, R₂NH (protonated secondary

s) **

dimethylammonium Dimethylamine is an organic compound with the formula (CH3)2NH. This secondary amine is a colorless, flammable gas with an ammonia-like odor. Dimethylamine is commonly encountered commercially as a solution in water at concentrations up to aroun ...

(sometimes dimethylaminium), (CH₃)₂NH (protonated

dimethylamine Dimethylamine is an organic compound with the formula (CH3)2NH. This secondary amine is a colorless, flammable gas with an ammonia-like odor. Dimethylamine is commonly encountered commercially as a solution in water at concentrations up to aroun ...

) ** diethylammonium (sometimes diethylaminium), (C₂H₅)₂NH (protonated

diethylamine Diethylamine is an organic compound with the formula (CH3CH2)2NH. It is a secondary amine. It is a flammable, weakly alkaline liquid that is miscible with most solvents. It is a colorless liquid, but commercial samples often appear brown due to im ...

) ** ethylmethylammonium, C₂H₅CH₃NH (protonated

ethylmethylamine Ethylmethylamine, or ''N''-methylethanamine, is a compound with the chemical formula C3H9N. It is corrosive and highly Combustibility and flammability, flammable. References

Alkylamines Secondary amines {{amine-stub ...

) ** diethanolammonium (sometimes diethanolaminium), (C₂H₄OH)₂NH (protonated

diethanolamine Diethanolamine, often abbreviated as DEA or DEOA, is an organic compound with the formula HN(CH2CH2OH)2. Pure diethanolamine is a white solid at room temperature, but its tendencies to absorb water and to supercool meaning that it is often encou ...

) *tertiary ammonium cations, R₃NH⁺ (protonated tertiary

s) **

trimethylammonium Trimethylamine (TMA) is an organic compound with the formula N(CH3)3. It is a colorless, hygroscopic, and flammable tertiary amine. It is a gas at room temperature but is usually sold as a 40% solution in water. (It is also sold in pressurized ...

(CH₃)₃NH⁺ (protonated

trimethylamine Trimethylamine (TMA) is an organic compound with the formula N(CH3)3. It is a colorless, hygroscopic, and flammable tertiary amine. It is a gas at room temperature but is usually sold as a 40% solution in water. (It is also sold in pressurized ...

) ** triethylammonium (C₂H₅)₃NH⁺ (protonated

triethylamine Triethylamine is the chemical compound with the formula N(CH2CH3)3, commonly abbreviated Et3N. It is also abbreviated TEA, yet this abbreviation must be used carefully to avoid confusion with triethanolamine or tetraethylammonium, for which TEA ...

) *

quaternary ammonium cation In chemistry, quaternary ammonium cations, also known as quats, are positively charged polyatomic ions of the structure , R being an alkyl group or an aryl group. Unlike the ammonium ion () and the primary, secondary, or tertiary ammonium cations ...

s, R₄N⁺ or NR **

tetrafluoroammonium The tetrafluoroammonium cation (also known as perfluoroammonium) is a positively charged polyatomic ion with chemical formula . It is equivalent to the ammonium ion where the hydrogen atoms surrounding the central nitrogen atom have been replaced ...

, NF **

tetramethylammonium Tetramethylammonium (TMA) or (Me4N+) is the simplest quaternary ammonium cation, consisting of four methyl groups attached to a central nitrogen atom, and is isoelectronic with neopentane. It is positively charged and can only be isolated in asso ...

, (CH₃)₄N⁺ **

tetraethylammonium Tetraethylammonium (TEA), () or (Et4N+) is a quaternary ammonium cation consisting of four ethyl groups attached to a central nitrogen atom, and is positively charged. It is a counterion used in the research laboratory to prepare lipophilic salts ...

, (C₂H₅)₄N⁺ ** tetrapropylammonium, (C₃H₇)₄N⁺ **

tetrabutylammonium Tetrabutylammonium is a quaternary ammonium cation with the formula (C4H9)4sup>+. It is used in the research laboratory to prepare lipophilic salts of inorganic anions. Relative to tetraethylammonium derivatives, tetrabutylammonium salts are more ...

, (C₄H₉)₄N⁺ or abbreviated Bu₄N⁺ **

trimethyl ammonium compounds Trimethyl ammonium compounds are a type of quaternary ammonium compound with three methyl groups at the nitrogen, with a more complicated carbon chain derivative at the fourth position. Examples include: * Betaine * Bethanechol * Carnitine an ...

, (CH₃)₃RN⁺ ** didecyldimethylammonium, (C₁₀H₂₁)₂(CH₃)₂N⁺ ** pentamethylhydrazinium, N(CH₃)₂N(CH₃) *quaternary phosphonium cations, R₄P⁺ or PR **

, *primary oxonium cations, (protonated R-O-H oxygen compounds) **alkyloxonium cations (protonated

alcohols In chemistry, an alcohol is a type of organic compound that carries at least one hydroxyl () functional group bound to a saturated carbon atom. The term ''alcohol'' originally referred to the primary alcohol ethanol (ethyl alcohol), which is ...

) ***methyloxonium, (protonated

methanol Methanol (also called methyl alcohol and wood spirit, amongst other names) is an organic chemical and the simplest aliphatic alcohol, with the formula C H3 O H (a methyl group linked to a hydroxyl group, often abbreviated as MeOH). It is a ...

) ***ethyloxonium, (protonated

ethanol Ethanol (abbr. EtOH; also called ethyl alcohol, grain alcohol, drinking alcohol, or simply alcohol) is an organic compound. It is an Alcohol (chemistry), alcohol with the chemical formula . Its formula can be also written as or (an ethyl ...

) *secondary oxonium cations, (protonated R-O-R oxygen compounds) **dialkyloxonium cations (protonated

ether In organic chemistry, ethers are a class of compounds that contain an ether group—an oxygen atom connected to two alkyl or aryl groups. They have the general formula , where R and R′ represent the alkyl or aryl groups. Ethers can again be c ...

s) ***dimethyloxonium, (protonated

dimethyl ether Dimethyl ether (DME; also known as methoxymethane) is the organic compound with the formula CH3OCH3, (sometimes ambiguously simplified to C2H6O as it is an isomer of ethanol). The simplest ether, it is a colorless gas that is a useful precursor ...

) *tertiary oxonium cations, **

trifluorooxonium The trifluorooxonium cation is a hypothetical positively charged polyatomic ion with chemical formula . It is structurally equivalent to the hydronium ion where the hydrogen atoms surrounding the central oxygen atom have been replaced by fluorine, ...

, (hypothetical) ** trimethyloxonium, ** triethyloxonium, ** oxatriquinacene, (cyclic) ** oxatriquinane, (cyclic) *secondary sulfonium cations, R₂SH⁺ (protonated

sulfide Sulfide (British English also sulphide) is an inorganic anion of sulfur with the chemical formula S2− or a compound containing one or more S2− ions. Solutions of sulfide salts are corrosive. ''Sulfide'' also refers to chemical compounds lar ...

s) ** dimethylsulfonium, (CH₃)₂SH⁺ (protonated dimethyl sulfide) *tertiary sulfonium cations, R₃S⁺ **

trimethylsulfonium Trimethylsulfonium (systematically named trimethylsulfanium and trimethylsulfur(1+)) is an organic cation with the chemical formula (CH3)3S+ (also written as ). Compounds Several salts of trimethylsulfonium are known. X-ray crystallography ...

, (CH₃)₃S⁺ *secondary fluoronium cations, R₂F⁺ ** dichlorofluoronium, Cl₂F⁺

Onium cations with polyvalent substitutions

*secondary ammonium cations having one double-bonded substitution, **diazenium, (protonated

diazene Diimide, also called diazene or diimine, is a compound having the formula (NH)2. It exists as two geometric isomers, ''E'' (''trans'') and ''Z'' (''cis''). The term diazene is more common for organic derivatives of diimide. Thus, azobenzene is ...

) **

guanidinium Guanidine is the compound with the formula HNC(NH2)2. It is a colourless solid that dissolves in polar solvents. It is a strong base that is used in the production of plastics and explosives. It is found in urine predominantly in patients experie ...

, (protonated

guanidine Guanidine is the compound with the formula HNC(NH2)2. It is a colourless solid that dissolves in polar solvents. It is a strong base that is used in the production of plastics and explosives. It is found in urine predominantly in patients experie ...

) (has a

resonance Resonance describes the phenomenon of increased amplitude that occurs when the frequency of an applied periodic force (or a Fourier component of it) is equal or close to a natural frequency of the system on which it acts. When an oscillatin ...

structure) *tertiary ammonium cations having one triple-bonded substitution, R≡NH+ **

, RC≡NH⁺ (protonated

nitrile In organic chemistry, a nitrile is any organic compound that has a functional group. The prefix ''cyano-'' is used interchangeably with the term ''nitrile'' in industrial literature. Nitriles are found in many useful compounds, including met ...

) **

diazonium Diazonium compounds or diazonium salts are a group of organic compounds sharing a common functional group where R can be any organic group, such as an alkyl or an aryl, and X is an inorganic or organic anion, such as a halide. General properti ...

, N≡NH⁺ (protonated

nitrogen Nitrogen is the chemical element with the symbol N and atomic number 7. Nitrogen is a nonmetal and the lightest member of group 15 of the periodic table, often called the pnictogens. It is a common element in the universe, estimated at se ...

) *tertiary ammonium cations having two partially double-bonded substitutions, RNH⁺R **

pyridinium Pyridinium refers to the cation . It is the conjugate acid of pyridine. Many related cations are known involving substituted pyridines, e.g. picolines, lutidines, collidines. They are prepared by treating pyridine with acids. As pyridine is oft ...

, C₅H₅NH⁺ (protonated

pyridine Pyridine is a basic heterocyclic organic compound with the chemical formula . It is structurally related to benzene, with one methine group replaced by a nitrogen atom. It is a highly flammable, weakly alkaline, water-miscible liquid with a d ...

) *quaternary ammonium cations having one double-bonded substitution and two single-bonded substitutions, **

, (substituted protonated

imine In organic chemistry, an imine ( or ) is a functional group or organic compound containing a carbon–nitrogen double bond (). The nitrogen atom can be attached to a hydrogen or an organic group (R). The carbon atom has two additional single bo ...

) **diazenium, (substituted protonated diazene) **thiazolium, (substituted protonated

thiazole Thiazole, or 1,3-thiazole, is a heterocyclic compound that contains both sulfur and nitrogen. The term 'thiazole' also refers to a large family of derivatives. Thiazole itself is a pale yellow liquid with a pyridine-like odor and the molecular for ...

) *quaternary ammonium cations having two double-bonded substitutions, R=N=R⁺ ** nitronium, ** bis(triphenylphosphine)iminium, ((C₆H₅)₃P)₂N⁺ *quaternary ammonium cations having one triple-bonded substitution and one single-bonded substitution, R≡NR⁺ **

, N≡NR⁺ (substituted protonated nitrogen) **nitrilium, RC≡NR⁺ (substituted protonated nitrile) *tertiary oxonium cations having one triple-bonded substitution, R≡O⁺ **

acylium ion In chemistry, an acyl group is a moiety derived by the removal of one or more hydroxyl groups from an oxoacid, including inorganic acids. It contains a double-bonded oxygen atom and an alkyl group (). In organic chemistry, the acyl group (IUPAC n ...

s, R−C≡O⁺ ↔ R−C⁺=O ** nitrosonium, N≡O⁺ *tertiary oxonium cations having two partially double-bonded substitutions, RO⁺R **

pyrylium Pyrylium is a cation (positive ion) with formula , consisting of a six-membered ring of five carbon atoms, each with one hydrogen atom, and one positively charged oxygen atom. The bonds in the ring are conjugated as in benzene, giving it an aroma ...

, C₅H₅O⁺ *tertiary sulfonium cations having one triple-bonded substitution, R≡S⁺ ** thionitrosyl, N≡S⁺

Double onium dications

hydrazinediium Hydrazinium is the cation with the formula . This cation has a methylamine-like structure (). It can be derived from hydrazine by protonation (treatment with a strong acid). Hydrazinium is a weak acid with PKa, p''K''a = 8.1. Salt (chemistry), S ...

or hydrazinium(2+)

dication A dication is any cation, of general formula X2+, formed by the removal of two electrons from a neutral species. Diatomic dications corresponding to stable neutral species (e.g. formed by removal of two electrons from H2) often decay quickly into ...

, ⁺H₃NNH (doubly protonated hydrazine) * diazenediium cation, ⁺H₂N=NH (doubly protonated diazene) * diazynediium cation, ⁺HN≡NH⁺ (doubly protonated iitrogen)

Enium cations

The extra bond is added to a less-common parent hydride, a

carbene analog Carbene analogs in chemistry are carbenes with the carbon atom replaced by another chemical element. Just as regular carbenes they appear in chemical reactions as reactive intermediates and with special precautions they can be stabilized and isolat ...

, typically named ''-ene'' or ''-ylene'', which is neutral with 2 fewer bonds than the more-common hydride, typically named ''-ane'' or ''-ine''. * borenium cations, (protonated

borylene A borylene is the boron analogue of a carbene. The general structure is R-B: with R an organic residue and B a boron atom with two unshared electrons. Borylenes are of academic interest in organoboron chemistry. A singlet ground state is predomi ...

s a.k.a. boranylidenes) *

carbenium A carbenium ion is a positive ion with the structure RR′R″C+, that is, a chemical species with a trivalent carbon that bears a +1 formal charge. In older literature the name carbonium ion was used for this class, but now it refers exclusivel ...

cations, (protonated

carbene In organic chemistry, a carbene is a molecule containing a neutral carbon atom with a valence of two and two unshared valence electrons. The general formula is or where the R represents substituents or hydrogen atoms. The term "carbene" ma ...

s) have a trivalent carbon atom with a +1 charge. **alkenium cations, (''n'' ≥ 2) (protonated

alkene In organic chemistry, an alkene is a hydrocarbon containing a carbon–carbon double bond. Alkene is often used as synonym of olefin, that is, any hydrocarbon containing one or more double bonds.H. Stephen Stoker (2015): General, Organic, an ...

s) ***

methenium In organic chemistry, methenium (also called methylium, carbenium, methyl cation, or protonated methylene) is a cation with the formula . It can be viewed as a methylene radical (:) with an added proton (), or as a methyl radical (•) with on ...

cation, (protonated methylene) ***

ethenium In chemistry, ethenium, protonated ethylene or ethyl cation is a positive ion with the formula . It can be viewed as a molecule of ethylene () with one added proton (), or a molecule of ethane () minus one hydride ion (). It is a carbocation; ...

, (protonated

ethene Ethylene (IUPAC name: ethene) is a hydrocarbon which has the formula or . It is a colourless, flammable gas with a faint "sweet and musky" odour when pure. It is the simplest alkene (a hydrocarbon with carbon-carbon double bonds). Ethylene is ...

) ** benzenium, (protonated

benzene Benzene is an organic chemical compound with the molecular formula C6H6. The benzene molecule is composed of six carbon atoms joined in a planar ring with one hydrogen atom attached to each. Because it contains only carbon and hydrogen atoms, ...

) **

tropylium In organic chemistry, the tropylium ion or cycloheptatrienyl cation is an aromatic species with a formula of 7H7sup>+. Its name derives from the molecule tropine from which cycloheptatriene (tropylidene) was first synthesized in 1881. Salts of ...

, * silylium cations, (protonated

silylene Silylene is a chemical compound with the formula SiH2. It is the silicon analog of methylene, the simplest carbene. Silylene is a stable molecule as a gas but rapidly reacts in a bimolecular manner when condensed. Unlike carbenes, which can exis ...

s) * nitrenium cations, (protonated

nitrene In chemistry, a nitrene or imene () is the nitrogen analogue of a carbene. The nitrogen atom is uncharged and univalent, so it has only 6 electrons in its valence level—two covalent bonded and four non-bonded electrons. It is therefore consid ...

s) * phosphinidenium cations, (protonated

phosphinidene Phosphinidenes (IUPAC: phosphanylidenes, formerly phosphinediyls) are low-valent phosphorus compounds analogous to carbenes and nitrenes, having the general structure RP. The "free" form of these compounds is conventionally described as having a si ...

) * mercurinium cations, (protonated

organomercury Organomercury refers to the group of organometallic compounds that contain mercury. Typically the Hg–C bond is stable toward air and moisture but sensitive to light. Important organomercury compounds are the methylmercury(II) cation, CH3Hg+; ...

compounds; formed as intermediates in

oxymercuration reaction The oxymercuration reaction is an electrophilic addition organic reaction that transforms an alkene into a neutral alcohol. In oxymercuration, the alkene reacts with mercuric acetate (AcO–Hg–OAc) in aqueous solution to yield the addition of an ...

Substituted eniums

*diphenylcarbenium, (di-substituted methenium) *

triphenylcarbenium In chemistry, triphenylcarbenium, triphenylmethyl cation, tritylium , or trityl cation is an ion with formula or , consisting of a carbon atom with a positive charge connected to three phenyl groups. It is a charged version of the triphenylmeth ...

, (tri-substituted methenium)

Ynium cations

* carbynium ions (protonated

carbyne In organic chemistry, a carbyne is a general term for any compound whose structure consists of an electrically neutral carbon atom connected by a single covalent bond and has three non-bonded electrons. The carbon atom has either one or thre ...

s) have a divalent carbon atom with a +1 charge. **alkynium cations, (''n'' ≥ 2) (protonated

alkyne \ce \ce Acetylene \ce \ce \ce Propyne \ce \ce \ce \ce 1-Butyne In organic chemistry, an alkyne is an unsaturated hydrocarbon containing at least one carbon—carbon triple bond. The simplest acyclic alkynes with only one triple bond and n ...

s) *** methynium cation, (protonated

methylidyne radical Methylidyne, or (unsubstituted) carbyne, is an organic compound whose molecule consists of a single hydrogen atom bonded to a carbon atom. It is the parent compound of the carbynes, which can be seen as obtained from it by substitution of other ...

) *** ethynium, (protonated

ethyne Acetylene ( systematic name: ethyne) is the chemical compound with the formula and structure . It is a hydrocarbon and the simplest alkyne. This colorless gas is widely used as a fuel and a chemical building block. It is unstable in its pure ...

)

References

External links

Ions and Radicals
Queen Mary University of London * {{Authority control Cations Chemical nomenclature

Simple onium cations (hydrides with no substitutions)

Group 13 The Group 13 network ( pl, Trzynastka, Yiddish: ''דאָס דרײַצענטל'') was a Jewish Nazi collaborationist organization in the Warsaw Ghetto during the German occupation of Poland in World War II. The rise and fall of the Group ... (boron group) onium cations

Group 14 The carbon group is a group (periodic table), periodic table group consisting of carbon (C), silicon (Si), germanium (Ge), tin (Sn), lead (Pb), and flerovium (Fl). It lies within the p-block. In modern International Union of Pure and Applied Chem ... (carbon group) onium cations

Group 15 A pnictogen ( or ; from grc, πνῑ́γω "to choke" and -gen, "generator") is any of the chemical elements in group 15 of the periodic table. Group 15 is also known as the nitrogen group or nitrogen family. Group 15 consists of the ... (pnictogen) onium cations

Group 16 The chalcogens (ore forming) ( ) are the chemical elements in group 16 of the periodic table. This group is also known as the oxygen family. Group 16 consists of the elements oxygen (O), sulfur (S), selenium (Se), tellurium (Te), and the radioa ... (chalcogen) onium cations

Pseudohalogen Pseudohalogens are polyatomic analogues of halogens, whose chemistry, resembling that of the true halogens, allows them to substitute for halogens in several classes of chemical compounds. Pseudohalogens occur in pseudohalogen molecules, inorganic ... onium cations

Group 18 The noble gases (historically also the inert gases; sometimes referred to as aerogens) make up a class of chemical elements with similar properties; under standard conditions, they are all odorless, colorless, monatomic gases with very low chemi ... (noble gas) onium cations

Hydrogen onium cation

Onium cations with monovalent substitutions

Onium cations with polyvalent substitutions

Double onium dications

Enium cations

Substituted eniums

Ynium cations

See also

References

External links

Group 13 The Group 13 network ( pl, Trzynastka, Yiddish: ''דאָס דרײַצענטל'') was a Jewish Nazi collaborationist organization in the Warsaw Ghetto during the German occupation of Poland in World War II. The rise and fall of the Group ...
(boron group) onium cations

Group 14 The carbon group is a group (periodic table), periodic table group consisting of carbon (C), silicon (Si), germanium (Ge), tin (Sn), lead (Pb), and flerovium (Fl). It lies within the p-block. In modern International Union of Pure and Applied Chem ...
(carbon group) onium cations

Group 15 A pnictogen ( or ; from grc, πνῑ́γω "to choke" and -gen, "generator") is any of the chemical elements in group 15 of the periodic table. Group 15 is also known as the nitrogen group or nitrogen family. Group 15 consists of the ...
(pnictogen) onium cations

Group 16 The chalcogens (ore forming) ( ) are the chemical elements in group 16 of the periodic table. This group is also known as the oxygen family. Group 16 consists of the elements oxygen (O), sulfur (S), selenium (Se), tellurium (Te), and the radioa ...
(chalcogen) onium cations

Pseudohalogen Pseudohalogens are polyatomic analogues of halogens, whose chemistry, resembling that of the true halogens, allows them to substitute for halogens in several classes of chemical compounds. Pseudohalogens occur in pseudohalogen molecules, inorganic ...
onium cations

Group 18 The noble gases (historically also the inert gases; sometimes referred to as aerogens) make up a class of chemical elements with similar properties; under standard conditions, they are all odorless, colorless, monatomic gases with very low chemi ...
(noble gas) onium cations