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In chemistry, 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 conve ...
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 ...
),
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 radioa ...
(group 16), or halogen (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 quaternar ...
, , 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 nitrogeno ...
, . 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 a ...
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 conve ...
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 analo ...
ous to ions and ate complexes: * Lewis bases form onium ions when the central atom gains one more bond and becomes a positive
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 conve ...
. *Lewis acids form ions when the central atom gains one more bond and becomes a negative
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 conve ...
.


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 Gro ...
(boron group) onium cations

* boronium 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 bon ...
)


Group 14 The carbon group is a 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 IUPAC notation, it is called group 14. In the field of semico ...
(carbon group) onium cations

* carbonium ions (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 ...
s) have a pentavalent carbon atom with a +1 charge. **alkanium cations, (protonated
alkane In organic chemistry Organic chemistry is a subdiscipline within chemistry involving the science, scientific study of the structure, properties, and reactions of organic compounds and organic materials, i.e., matter in its various forms tha ...
s) *** methanium, (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 Ear ...
) (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, (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 petro ...
) *** 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 as ...
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 bu ...
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 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) * 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) * 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 ...
) * stannonium, (protonated ) (not protonated stannane ) * plumbonium, (protonated )


Group 15 (pnictogen) onium cations

*
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 quaternar ...
(
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
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 nitrogeno ...
(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 rotti ...
) *
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 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–S ...
) * 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 expe ...
)


Group 16 (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 ...
(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 di ...
, though hydronium implies a solvated or hydrated proton. It may also be called hydroxonium.) * sulfonium, (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 und ...
) * 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)


Group 17 (halogen) onium cations, halonium ions, 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 astati ...
s)

* fluoronium, (protonated hydrogen fluoride) * chloronium, (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 g ...
) * bromonium, (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 tempe ...
) * iodonium, (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 s ...
)


Pseudohalogen 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 a ...
)


Group 18 (noble gas) onium cations

* hydrohelium or helonium, 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 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 krypt ...
) * argonium, 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 a ...
) *
kryptonium Kryptonite is a fictional material that appears primarily in Superman stories published by DC Comics. In its best-known form, it is a green, crystalline material originating from Superman's home world of Krypton (comics), Krypton that emits a u ...
, 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 The xenonium ion, XeH+, is an onium compound, consisting of protonated xenon. Although the existence of the xenonium cation itself has not been proven, salts of the fluoroxenonium ion, XeF+, are known to exist, for instance fluoroxenonium pentafluo ...
, 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, 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 ...
), 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 su ...
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, 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 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. It is an industrially significant commodity chemical, as well as a versatile start ...
, a.k.a. phenylamine, aminobenzene) *secondary ammonium cations, R2NH (protonated secondary
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 su ...
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 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 flammable A combustible material is something that can burn (i.e., ''combust'') in air. A combustible material is flamma ...
) ** diethanolammonium (sometimes diethanolaminium), (C2H4OH)2NH (protonated diethanolamine) *tertiary ammonium cations, R3NH+ (protonated tertiary
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 su ...
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 g ...
(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 cat ...
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 assoc ...
, (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, (C4H9)4N+ or abbreviated Bu4N+ ** trimethyl ammonium compounds, (CH3)3RN+ **
didecyldimethylammonium Didecyldimethylammonium chloride (DDAC) is a quaternary ammonium compound used as antiseptic/disinfectant. It causes the disruption of intermolecular interactions and the dissociation of lipid bilayers. The bacteriostatic (prevent growth) or ba ...
, (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 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 i ...
) ***methyloxonium, (protonated methanol) ***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 h ...
) *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 b ...
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 precurs ...
) *tertiary oxonium cations, ** trifluorooxonium, (hypothetical) ** trimethyloxonium, ** triethyloxonium, **
oxatriquinacene Oxatriquinacene is an organic cation with formula . It is an oxonium ion, with a trivalent oxygen atom with +1 charge connected to carbons 1,4, and 7 of a cyclononatriene ring, forming three fused pentagonal cycles. The compound may possess ...
, (cyclic) **
oxatriquinane Oxatriquinane (oxoniaperhydrotriquinacene) is an alkyl oxonium ion with formula (CH2CH2CH)3O+. It has a cyclononane backbone, with a trivalent oxygen connected to carbon 1, 4, and 7, forming three fused pentagonal rings. In contrast to most trial ...
, (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 l ...
s) ** 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 co ...
) *tertiary sulfonium cations, R3S+ ** trimethylsulfonium, (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 i ...
) **
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 experi ...
, (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 oscillat ...
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 me ...
) **
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 seve ...
) *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 (chemistry), basic heterocyclic compound, 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, weakl ...
) *quaternary ammonium cations having one double-bonded substitution and two single-bonded substitutions, **
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 a ...
, (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 fo ...
) *quaternary ammonium cations having two double-bonded substitutions, R=N=R+ **
nitronium The nitronium ion, , is a cation. It is an onium ion because its nitrogen atom has +1 charge, similar to ammonium ion . It is created by the removal of an electron from the paramagnetic nitrogen dioxide molecule , or the protonation of nitric aci ...
, **
bis(triphenylphosphine)iminium Bis(triphenylphosphine)iminium chloride is the chemical compound with the formula , often abbreviated , where Ph is phenyl , or even abbreviated PNl or NPl or PPNCl or PNPCl, where PPN or PNP stands for . This colorless salt is a source of the c ...
, ((C6H5)3P)2N+ *quaternary ammonium cations having one triple-bonded substitution and one single-bonded substitution, R≡NR+ **
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≡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, 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" may ...
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 one ...
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 is ...
) **
benzenium An arenium ion in organic chemistry is a cyclohexadienyl cation that appears as a reactive intermediate in electrophilic aromatic substitution. For historic reasons this complex is also called a Wheland intermediate, after American chemist George ...
, (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 ato ...
) ** tropylium, * 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 A nitrenium ion (also called: aminylium ion or imidonium ion (obsolete)) in organic chemistry is a reactive intermediate based on nitrogen with both an electron lone pair and a positive charge and with two substituents (). Nitrenium ions are i ...
cations, (protonated nitrenes) * phosphinidenium cations, (protonated phosphinidene) * mercurinium cations, (protonated organomercury compounds; formed as intermediates in oxymercuration reactions)


Substituted eniums

*diphenylcarbenium, (di-substituted methenium) * triphenylcarbenium, (tri-substituted methenium)


Ynium cations

* carbynium ions (protonated carbynes) 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 no ...
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 ...
)


See also

* Carbonium ion *
Lyonium ion In chemistry, a lyonium ion is the cation derived by the protonation of a solvent molecule. For example, a hydronium ion is formed by the protonation of water, and is the cation formed by the protonation of methanol. Its counterpart is a lyate i ...
, a protonated solvent molecule *
Lyate ion In chemistry, a lyate ion is the anion derived by the deprotonation of a solvent molecule. For example, a hydroxide ion is formed by the deprotonation of water, and methoxide () is the anion formed by the deprotonation of methanol. Its coun ...
, a deprotonated solvent molecule


References


External links


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