chemistry Chemistry is the scientific study of the properties and behavior of matter. It is a natural science that covers the elements that make up matter to the compounds made of atoms, molecules and ions: their composition, structure, propertie ...

, 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 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 radi ...

(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 grou ...

(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 ...

, , 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 w ...

, . 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, . 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 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 analogous to ions and ate complexes: * Lewis bases 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 (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 de ...

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 indicate ...

) **further boronium cations, (protonated boranes)

Group 14 (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 ne ...

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 ...

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 whi ...

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 o ...

, (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 ...

) (Sometimes called carbonium, 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 simp ...

, (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 ...

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 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 ...

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 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, ...

) * silanium (sometimes silonium), (protonated silane) (should not be called siliconiumRC-82. Cations
Queen Mary University of London) ** disilanium, (protonated disilane) **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) * stannonium, (protonated ) (not protonated stannane ) * 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 el ...
(pnictogen) onium cations

( IUPAC 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 c ...

, (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 a ...

, (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 t ...

) * stibonium, (protonated

stibine Stibine (IUPAC name: stibane) is a chemical compound with the formula SbH3. A pnictogen hydride, this colourless, highly toxic gas is the principal covalent hydride of antimony, and a heavy analogue of ammonia. The molecule is pyramidal with H– ...

) * 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 radioac ...
(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, though hydronium implies a solvated or hydrated proton. It may also be called hydroxonium.) *

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) * 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 sele ...

) * telluronium, (protonated

hydrogen telluride Hydrogen telluride is the inorganic compound with the formula H2 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 low concentrations long enough ...

)

Group 17 (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. Halon ...
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 mol ...

, (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) * bromonium, (protonated hydrogen bromide) * iodonium, (protonated hydrogen iodide)

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) *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 in ...

)

Group 18 (noble gas) onium cations

* hydrohelium or

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 ...

, 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, NeH⁺ (protonated neon) *

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 molecular ...

, 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 ...

) * 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 u ...

) * 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 f ...

) *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-toxi ...

), 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 substituent such ...

s) ** hydroxylammonium, NH₃OH⁺ (protonated hydroxylamine) ** 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, e ...

) ** ethylammonium, C₂H₅NH (protonated

ethylamine Ethylamine, also known as ethanamine, is an organic compound with the formula CH3CH2NH2. This colourless gas has a strong ammonia-like odor. It condenses just below room temperature to a liquid miscible with virtually all solvents. It is a nucl ...

) ** hydrazinium, 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, hydrazin ...

, a.k.a. diazane) **anilinium (a.k.a. phenylammonium), (protonated aniline, a.k.a. phenylamine, aminobenzene) *secondary ammonium cations, R₂NH (protonated secondary

s) ** dimethylammonium (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 arou ...

) ** 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) ** 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 (CH₃)₃NH⁺ (protonated trimethylamine) ** 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 cati ...

s, R₄N⁺ or NR ** tetrafluoroammonium, 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, (C₂H₅)₄N⁺ ** tetrapropylammonium, (C₃H₇)₄N⁺ ** tetrabutylammonium, (C₄H₉)₄N⁺ or abbreviated Bu₄N⁺ ** trimethyl ammonium compounds, (CH₃)₃RN⁺ ** didecyldimethylammonium, (C₁₀H₂₁)₂(CH₃)₂N⁺ ** pentamethylhydrazinium, N(CH₃)₂N(CH₃) *quaternary phosphonium cations, R₄P⁺ or PR ** tetraphenylphosphonium, *primary oxonium cations, (protonated R-O-H oxygen compounds) **alkyloxonium cations (protonated alcohols) ***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 ...

) ***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 with the chemical formula . Its formula can be also written as or (an ethyl group linked to a ...

) *secondary oxonium cations, (protonated R-O-R oxygen compounds) **dialkyloxonium cations (protonated ethers) ***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, (hypothetical) ** trimethyloxonium, ** triethyloxonium, ** oxatriquinacene, (cyclic) ** oxatriquinane, (cyclic) *secondary sulfonium cations, R₂SH⁺ (protonated sulfides) ** dimethylsulfonium, (CH₃)₂SH⁺ (protonated

dimethyl sulfide Dimethyl sulfide (DMS) or methylthiomethane is an organosulfur compound with the formula (CH3)2S. Dimethyl sulfide is a flammable liquid that boils at and has a characteristic disagreeable odor. It is a component of the smell produced from coo ...

) *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 r ...

, (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, (protonated guanidine) (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 oscilla ...

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

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

) *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 bon ...

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

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

Double onium dications

* hydrazinediium 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, 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 borylenes a.k.a. boranylidenes) * carbenium 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 cation, (protonated methylene) *** ethenium, (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 ...

) ** 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 a ...

) ** tropylium, * silylium cations, (protonated silylenes) * 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 co ...

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+; e ...

compounds; formed as intermediates in oxymercuration reactions)

Substituted eniums

*diphenylcarbenium, (di-substituted methenium) * triphenylcarbenium, (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 three ...

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)

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 (boron group) onium cations

Group 14 (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 el ... (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 radioac ... (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 (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 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 el ...
(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 radioac ...
(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