chemistry Chemistry is the scientific study of the properties and behavior of matter. It is a physical science within the natural sciences that studies the chemical elements that make up matter and chemical compound, compounds made of atoms, molecules a ...

, 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), usually denoted by H+, to an atom, molecule, or ion, forming a conjugate acid. (The complementary process, when a proton is removed from a Brø ...

of mononuclear parent

hydride In chemistry, a hydride is formally the anion of hydrogen (H−), a hydrogen ion with two electrons. In modern usage, this is typically only used for ionic bonds, but it is sometimes (and has been more frequently in the past) applied to all che ...

of a

pnictogen , - ! colspan=2 style="text-align:left;" , ↓ Period , - ! 2 , , - ! 3 , , - ! 4 , , - ! 5 , , - ! 6 , , - ! 7 , , - , colspan="2", ---- ''Legend'' A pnictogen ( or ; from "to choke" and -gen, "generator") is any ...

(group 15 of the

periodic table The periodic table, also known as the periodic table of the elements, is an ordered arrangement of the chemical elements into rows (" periods") and columns (" groups"). It is an icon of chemistry and is widely used in physics and other s ...

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 rad ...

(group 16), or

halogen The halogens () are a group in the periodic table consisting of six chemically related elements: fluorine (F), chlorine (Cl), bromine (Br), iodine (I), and the radioactive elements astatine (At) and tennessine (Ts), though some authors would ...

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

ammonium Ammonium is a modified form of ammonia that has an extra hydrogen atom. It is a positively charged (cationic) polyatomic ion, molecular ion with the chemical formula or . It is formed by the protonation, addition of a proton (a hydrogen nucleu ...

, , the protonated derivative of

ammonia Ammonia is an inorganic chemical compound of nitrogen and hydrogen with the chemical formula, formula . A Binary compounds of hydrogen, stable binary hydride and the simplest pnictogen hydride, ammonia is a colourless gas with a distinctive pu ...

, . 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 groups, or halogens; such as

tetraphenylphosphonium Tetraphenylphosphonium chloride is the chemical compound with the formula , abbreviated or or , where Ph stands for phenyl. Tetraphenylphosphonium and especially tetraphenylarsonium salts were formerly of interest in gravimetric analysis of perc ...

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

. 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 conven ...

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 ...

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 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 sp ...

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 (, ) was a Jewish collaborationist organization in the Warsaw Ghetto during the German occupation of Poland in World War II. The rise and fall of the Group was likely a proxy for power struggles between various facti ...
(boron group) onium cations

boronium In chemistry, a boranylium ion is an inorganic compound, 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 hist ...

cation, (protonated

borane Borane is an inorganic compound with the chemical formula . Because it tends to dimerize or form adducts, borane is very rarely observed. It normally dimerizes to diborane in the absence of other chemicals. It can be observed directly as a c ...

) **further boronium cations, (protonated

boranes A borane is a compound with the formula although examples include multi-boron derivatives. A large family of boron hydride clusters is also known. In addition to some applications in organic chemistry, the boranes have attracted much attention ...

)

Group 14 (carbon group) onium cations

carbonium ion In chemistry, a carbonium ion is a cation that has a pentacoordinated carbon atom. They are a type of carbocation. In older literature, the name "carbonium ion" was used for what is today called carbenium. Carbonium ions charge is delocalized ...

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 Hydrophobe, hydrophobic; their odor is usually fain ...

s) have a pentacoordinated 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 (metastable transitional form, a carbon atom covalently bonded to five hydrogen atoms) or (fluxional form, namely a molecule with one carbon atom covalently bonded to three hydro ...

, (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 abundance of methane on Earth makes ...

) (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 a naturally occurring Organic compound, organic chemical compound with chemical formula . At standard temperature and pressure, ethane is a colorless, odorless gas. Like many hydrocarbons, ethane is List of purification methods ...

) *** propanium, (

propane Propane () is a three-carbon chain alkane with the molecular formula . It is a gas at standard temperature and pressure, but becomes liquid when compressed for transportation and storage. A by-product of natural gas processing and petroleum ref ...

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 () is an alkane with the formula C4H10. Butane exists as two isomers, ''n''-butane with connectivity and iso-butane with the formula . Both isomers are highly flammable, colorless, easily liquefied gases that quickly vaporize at ro ...

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 colorless, odorless 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 a cation that has a Coordination number, pentacoordinated carbon atom. They are a type of carbocation. In older literature, the name "carbonium ion" was used for what is today called carbenium ion, carbenium. Car ...

or octanium, (protonated

octane Octane is a hydrocarbon and also an alkane with the chemical formula C8H18, and the condensed structural formula CH3(CH2)6CH3. Octane has many structural isomers that differ by the location of branching in the carbon chain. One of these isomers ...

) * silanium (sometimes silonium), (protonated

silane Silane (Silicane) is an inorganic compound with chemical formula . It is a colorless, pyrophoric gas with a sharp, repulsive, pungent smell, somewhat similar to that of acetic acid. Silane is of practical interest as a precursor to elemental ...

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

disilane Disilane is a chemical compound with general chemical formula Si2R6 that was first identified in 1902 by Henri Moissan and Samuel Smiles (1877–1953) where R = H. Moissan and Smiles reported disilane as being among the products formed by the actio ...

) **further silanium cations, (protonated

silanes In organosilicon chemistry, silanes are a diverse class of charge-neutral organic compounds with the general formula . The R substituents can be any combination of organic or inorganic groups. Most silanes contain Si-C bonds, and are discussed ...

) * 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 Sn H4. 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 ...

) * plumbonium, (protonated ) (not protonated

plumbane Plumbane is an inorganic chemical compound with the chemical formula PbH. It is a colorless gas. It is a metal hydride and group 14 hydride composed of lead and hydrogen. Plumbane is not well characterized or well known, and it is thermodynamicall ...

) * flerovonium, (protonated ) (not protonated flerovane )

Group 15 , - ! colspan=2 style="text-align:left;" , ↓ Period , - ! 2 , , - ! 3 , , - ! 4 , , - ! 5 , , - ! 6 , , - ! 7 , , - , colspan="2", ---- ''Legend'' A pnictogen ( or ; from "to choke" and -gen, "generator") is any ...
(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 chemistry, the term phosphonium (more obscurely: phosphinium) describes polyatomic cations with the chemical formula (where R is a hydrogen or an alkyl, aryl, organyl or halogen group). These cations have tetrahedral structures. The ...

, (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 th ...

) * stibonium, (protonated

stibine Stibine (IUPAC name: stibane) is a chemical compound with the formula Sb H3. 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 Bi H3. As the heaviest analogue of ammonia (a pnictogen hydride), BiH3 is unstable, decomposing to bismuth metal well below 0 °C. This compound adopts the expect ...

) * moscovonium, (protonated moscovine)

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 ...
(chalcogen) onium cations

* oxonium, (protonated

water Water is an inorganic compound with the chemical formula . It is a transparent, tasteless, odorless, and Color of water, nearly colorless chemical substance. It is the main constituent of Earth's hydrosphere and the fluids of all known liv ...

(IUPAC name oxidane). Oxonium is better known as

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

, though hydronium implies a solvated or hydrated

proton A proton is a stable subatomic particle, symbol , Hydron (chemistry), H+, or 1H+ with a positive electric charge of +1 ''e'' (elementary charge). Its mass is slightly less than the mass of a neutron and approximately times the mass of an e ...

. 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 Substitution (chemistry), substituents attached to sulfur. These organosulfur compounds have t ...

, (protonated

hydrogen sulfide Hydrogen sulfide is a chemical compound with the formula . It is a colorless chalcogen-hydride gas, and is toxic, corrosive, and flammable. Trace amounts in ambient atmosphere have a characteristic foul odor of rotten eggs. Swedish chemist ...

) * 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 se ...

) * 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 long enough to be readily detected by ...

) * polononium, (protonated hydrogen polonide) * livermoronium, (protonated hydrogen livermoride)

Hydrogen onium cation

*hydrogenonium, better known as

trihydrogen cation The trihydrogen cation or protonated molecular hydrogen ( IUPAC name: hydrogen onium ion) is a cation (positive ion) with formula , consisting of three hydrogen nuclei (protons) sharing two electrons. The trihydrogen cation is one of the most a ...

, (protonated molecular or diatomic

hydrogen Hydrogen is a chemical element; it has chemical symbol, symbol H and atomic number 1. It is the lightest and abundance of the chemical elements, most abundant chemical element in the universe, constituting about 75% of all baryon, normal matter ...

), found in ionized hydrogen and interstellar space

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

* fluoronium, (protonated

hydrogen fluoride Hydrogen fluoride (fluorane) is an Inorganic chemistry, inorganic compound with chemical formula . It is a very poisonous, colorless gas or liquid that dissolves in water to yield hydrofluoric acid. It is the principal industrial source of fluori ...

) *

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

) *

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. Halo ...

, (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 (HI) 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 und ...

) * astatonium, (protonated

hydrogen astatide Hydrogen astatide, also known as astatine hydride, astatane, astatidohydrogen or hydroastatic acid, is a chemical compound with the chemical formula HAt, consisting of an astatine atom covalently bonded to a hydrogen atom. It thus is a hydrogen ...

) * tennessonium, (protonated hydrogen tennesside)

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, inorgani ...
onium cations

* aminodiazonium, (protonated hydrogen azide) *methylidyneammonium and hydrocyanonium, , isomers (protonated

hydrogen cyanide Hydrogen cyanide (formerly known as prussic acid) is a chemical compound with the chemical formula, formula HCN and structural formula . It is a highly toxic and flammable liquid that boiling, boils slightly above room temperature, at . HCN is ...

)

Group 18 (noble gas) onium cations

hydrohelium The helium hydride ion, hydridohelium(1+) ion, or helonium is a Ion#Anions and cations, cation (electric charge, positively charged ion) with chemical formula HeH+. It consists of a helium atom covalent bond, bonded to a hydrogen atom, with on ...

or helonium, better known as

helium hydride ion The helium hydride ion, 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 protonate ...

, (protonated

helium Helium (from ) is a chemical element; it has chemical symbol, symbol He and atomic number 2. It is a colorless, odorless, non-toxic, inert gas, inert, monatomic gas and the first in the noble gas group in the periodic table. Its boiling point is ...

) *

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 ne ...

, (protonated

neon Neon is a chemical element; it has symbol Ne and atomic number 10. It is the second noble gas in the periodic table. Neon is a colorless, odorless, inert monatomic gas under standard conditions, with approximately two-thirds the density of ...

) * argonium, (protonated

argon Argon is a chemical element; it has 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, (protonated

krypton Krypton (from 'the hidden one') is a chemical element; it has symbol (chemistry), symbol Kr and atomic number 36. It is a colorless, odorless noble gas that occurs in trace element, trace amounts in the Earth's atmosphere, atmosphere and is of ...

) * xenonium, (protonated

xenon Xenon is a chemical element; it has 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 ...

) * radonium, (protonated

radon Radon is a chemical element; it has symbol Rn and atomic number 86. It is a radioactive noble gas and is colorless and odorless. Of the three naturally occurring radon isotopes, only Rn has a sufficiently long half-life (3.825 days) for it to b ...

) * oganessonium (protonated

oganesson Oganesson is a synthetic element, synthetic chemical element; it has Chemical symbol, symbol Og and atomic number 118. It was first synthesized in 2002 at the Joint Institute for Nuclear Research (JINR) in Dubna, near Moscow, Russia, by a joint ...

)

Onium cations with monovalent substitutions

*primary ammonium cations, or (protonated primary

amine In chemistry, amines (, ) are organic compounds that contain carbon-nitrogen bonds. Amines are formed when one or more hydrogen atoms in ammonia are replaced by alkyl or aryl groups. The nitrogen atom in an amine possesses a lone pair of elec ...

s) ** hydroxylammonium, (protonated

hydroxylamine Hydroxylamine (also known as hydroxyammonia) is an inorganic compound with the chemical formula . The compound exists as hygroscopic colorless crystals.Greenwood and Earnshaw. ''Chemistry of the Elements.'' 2nd Edition. Reed Educational and Prof ...

) ** methylammonium, (protonated

methylamine Methylamine, also known as methanamine, 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 ...

) ** ethylammonium, (protonated

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

) **

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, (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 hazardous unless handled in solution as, for example, hydraz ...

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

aniline Aniline (From , meaning ' indigo shrub', and ''-ine'' indicating a derived substance) is an organic compound with the formula . Consisting of a phenyl group () attached to an amino group (), aniline is the simplest aromatic amine. It is an in ...

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

(sometimes dimethylaminium), (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 around ...

) ** diethylammonium (sometimes diethylaminium), (protonated

diethylamine Diethylamine is an organic compound with the formula . It is classified as a secondary amine. It is a flammable, volatile weakly alkaline liquid that is miscible with most solvents. It is a colorless liquid, but commercial samples often appear br ...

) ** ethylmethylammonium, (protonated ethylmethylamine) ** diethanolammonium (sometimes diethanolaminium), (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 often results in it being foun ...

) *tertiary ammonium cations, (protonated tertiary

s) **

trimethylammonium Trimethylamine (TMA) is an organic compound with the formula N(CH3)3. It is a trimethylated derivative of ammonia. TMA is widely used in industry. At higher concentrations it has an ammonia-like odor, and can cause necrosis of mucous membranes ...

(protonated

trimethylamine Trimethylamine (TMA) is an organic compound with the formula N(CH3)3. It is a trimethylated derivative of ammonia. TMA is widely used in industry. At higher concentrations it has an ammonia-like odor, and can cause necrosis of mucous membranes ...

) ** triethylammonium (protonated

triethylamine Triethylamine is the chemical compound with the formula N(CH2CH3)3, commonly abbreviated Et3N. Like triethanolamine and the tetraethylammonium ion, it is often abbreviated TEA. It is a colourless volatile liquid with a strong fishy odor remini ...

) *

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

s, or **

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 ...

, **

tetramethylammonium Tetramethylammonium (TMA) is the simplest quaternary ammonium cation. It has the chemical formula and consists of four methyl groups (, denoted Me) attached to a central nitrogen atom. The cation is isoelectronic with neopentane (). It is positi ...

, **

tetraethylammonium Tetraethylammonium (TEA) is a quaternary ammonium cation with the chemical formula , consisting of four ethyl groups (, denoted Et) attached to a central nitrogen atom. It is a counterion used in the research laboratory to prepare lipophilic salt ...

, ** tetrapropylammonium, **

tetrabutylammonium Tetrabutylammonium is a quaternary ammonium cation with the formula , also denoted (where Bu = butyl group). It is used in the research laboratory to prepare lipophilic salts of inorganic anions. Relative to tetraethylammonium derivatives, tetr ...

, or abbreviated ** trimethyl ammonium compounds, ** didecyldimethylammonium, ** pentamethylhydrazinium, *quaternary phosphonium cations, or **

, *quaternary arsonium cations, or ** tetraphenylarsonium, *quaternary stibonium cations, or ** tetraphenylstibonium, *primary oxonium 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 and unsaturated compounds, saturated carbon atom. Alcohols range from the simple, like methanol and ethanol ...

) **alkyloxonium cations (protonated

) ***methyloxonium, (protonated

methanol Methanol (also called methyl alcohol and wood spirit, amongst other names) is an organic chemical compound and the simplest aliphatic Alcohol (chemistry), alcohol, with the chemical formula (a methyl group linked to a hydroxyl group, often ab ...

) ***ethyloxonium, (protonated

ethanol Ethanol (also called ethyl alcohol, grain alcohol, drinking alcohol, or simply alcohol) is an organic compound with the chemical formula . It is an Alcohol (chemistry), alcohol, with its formula also written as , or EtOH, where Et is the ps ...

) **dioxidanonium (hydroxylhydronium), (protonated

hydrogen peroxide Hydrogen peroxide is a chemical compound with the formula . In its pure form, it is a very pale blue liquid that is slightly more viscosity, viscous than Properties of water, water. It is used as an oxidizer, bleaching agent, and antiseptic, usua ...

) *secondary oxonium cations, (protonated

ethers In organic chemistry, ethers are a class of compounds that contain an ether group, a single oxygen atom bonded to two separate carbon atoms, each part of an organyl group (e.g., alkyl or aryl). They have the general formula , where R and R′ r ...

) **dialkyloxonium cations (protonated

ether In organic chemistry, ethers are a class of compounds that contain an ether group, a single oxygen atom bonded to two separate carbon atoms, each part of an organyl group (e.g., alkyl or aryl). They have the general formula , where R and R� ...

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 Oxatriquinacene is an organic cation with formula . It is an oxonium ion, with a tricoordinated oxygen atom with +1 charge connected to carbons 1,4, and 7 of a cyclononatriene ring, forming three fused pentagonal cycles. The compound may pos ...

, (cyclic oxonium ion) **

oxatriquinane Oxatriquinane (oxoniaperhydrotriquinacene) is an alkyl oxonium ion with formula (CH2CH2CH)3O+. It has a cyclononane backbone, with a tricoordinated oxygen connected to carbon 1, 4, and 7, forming three fused pentagonal rings. In contrast to most ...

, (cyclic oxonium ion) *primary sulfonium cations, (protonated

thiol In organic chemistry, a thiol (; ), or thiol derivative, is any organosulfur compound of the form , where R represents an alkyl or other organic substituent. The functional group itself is referred to as either a thiol group or a sulfhydryl grou ...

s ) *secondary sulfonium cations, (protonated

thioether In organic chemistry, a sulfide (British English sulphide) or thioether is an organosulfur functional group with the connectivity as shown on right. Like many other sulfur-containing compounds, Volatile organic compound, volatile sulfides have ...

s ) ** dimethylsulfonium, (protonated

dimethyl sulfide Dimethyl sulfide (DMS) or methylthiomethane is an organosulfur compound with the formula . It is the simplest thioether and has a characteristic disagreeable odor. It is a flammable liquid that boils at . It is a component of the smell produc ...

) *tertiary sulfonium cations, **

trimethylsulfonium Trimethylsulfonium (systematically named trimethylsulfanium) is an organic cation with the chemical formula (also written as ). Compounds Several salts of trimethylsulfonium are known. X-ray crystallography reveals that the ion has trigonal ...

, *tertiary selenonium cations, ** triphenylselenonium, *tertiary telluronium cations, ** triphenyltelluronium, *primary fluoronium cations, (protonated

fluorides Fluoride (). According to this source, is a possible pronunciation in British English. is an inorganic, monatomic anion of fluorine, with the chemical formula (also written ), whose salts are typically white or colorless. Fluoride salts typi ...

RF) *secondary fluoronium cations, ** dichlorofluoronium, *secondary

cations, ** diphenyliodonium,

Onium cations with polyvalent substitutions

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

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 experi ...

) (has a

resonance Resonance is a phenomenon that occurs when an object or system is subjected to an external force or vibration whose frequency matches a resonant frequency (or resonance frequency) of the system, defined as a frequency that generates a maximu ...

structure and a planar molecular geometry) *tertiary ammonium cations having one triple-bonded substitution, R≡NH+ **

, (protonated

nitrile In organic chemistry, a nitrile is any organic compound that has a functional group. The name of the compound is composed of a base, which includes the carbon of the , suffixed with "nitrile", so for example is called " propionitrile" (or pr ...

) **

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. The parent, compou ...

or diazynium, (protonated

nitrogen Nitrogen is a chemical element; it has Symbol (chemistry), symbol N and atomic number 7. Nitrogen is a Nonmetal (chemistry), nonmetal and the lightest member of pnictogen, group 15 of the periodic table, often called the Pnictogen, pnictogens. ...

, in other words, protonated diazyne) * cyclic tertiary ammonium cations where nitrogen is a member of a ring, (the ring may be

aromatic In organic chemistry, aromaticity is a chemical property describing the way in which a conjugated system, conjugated ring of unsaturated bonds, lone pairs, or empty orbitals exhibits a stabilization stronger than would be expected from conjugati ...

) **

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 often ...

, (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, weak ...

) *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 5-membered 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 ...

) *quaternary ammonium cations having two double-bonded substitutions, **

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 A molecule is a grou ...

, ** bis(triphenylphosphine)iminium, *quaternary ammonium cations having one triple-bonded substitution and one single-bonded substitution, **

, (substituted protonated nitrogen, in other words, substituted protonated diazyne) **nitrilium, (substituted protonated nitrile) *tertiary oxonium cations having one triple-bonded substitution, ** acylium ions, **

nitrosonium The nitrosonium ion is , in which the nitrogen atom is bonded to an oxygen atom with a bond order of 3, and the overall diatomic species bears a positive charge. It can be viewed as nitric oxide with one electron removed. This ion is usually o ...

, *cyclic tertiary oxonium cations where oxygen is a member of a ring, (the ring may be aromatic) **

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 ...

, *tertiary sulfonium cations having one triple-bonded substitution, ** thionitrosyl, * dihydroxyoxoammonium, (protonated

nitric acid Nitric acid is an inorganic compound with the formula . It is a highly corrosive mineral acid. The compound is colorless, but samples tend to acquire a yellow cast over time due to decomposition into nitrogen oxide, oxides of nitrogen. Most com ...

) * trihydroxyoxosulfonium, (protonated

sulfuric acid Sulfuric acid (American spelling and the preferred IUPAC name) or sulphuric acid (English in the Commonwealth of Nations, Commonwealth spelling), known in antiquity as oil of vitriol, is a mineral acid composed of the elements sulfur, oxygen, ...

)

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 int ...

, (doubly protonated

, in other words, doubly protonated diazane) * diazenediium cation, (doubly protonated diazene) * diazynediium cation, (doubly protonated

dinitrogen Nitrogen is a chemical element; it has 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 seventh ...

, in other words, doubly protonated diazyne)

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 isola ...

, 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 moiety (chemistry), moiety and B a boron atom with two unshared electrons. Borylenes are of academic interest in organoboron chemistry. A diradical, sin ...

s a.k.a. boranylidenes) *

carbenium The carbenium ion is a kind of positive ion with the structure RR′R″C+, that is, a chemical species with carbon atom having three covalent bonds, and it bears a +1 formal charge. Carbenium ions are a major subset of carbocations, which is a ...

cations, (protonated

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

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

alkene In organic chemistry, an alkene, or olefin, is a hydrocarbon containing a carbon–carbon double bond. The double bond may be internal or at the terminal position. Terminal alkenes are also known as Alpha-olefin, α-olefins. The Internationa ...

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 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; mo ...

, (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). Ethy ...

) **

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 compound, organic chemical compound with the Chemical formula#Molecular formula, molecular formula C6H6. The benzene molecule is composed of six carbon atoms joined in a planar hexagonal Ring (chemistry), ring with one hyd ...

) **

tropylium 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 the tropylium cation ...

, (protonated tropylidene) * silylium cations, (protonated

silylene Silylene is a chemical compound with the formula SiR2. It is the silicon analog of carbene. Silylene rapidly when condensed. Silylenes are formal derivatives of silylene with its hydrogens replaced by other substituents. Most examples feature ...

s) * nitrenium cations, (protonated

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

s) * phosphinidenium cations, (protonated phosphinidene) * mercurinium cations, (protonated

organomercury Organomercury chemistry refers to the study of organometallic compounds that contain mercury. Many organomercury compounds are highly toxic, but some are used in medicine, e.g., merbromin ("Mercurochrome") and the vaccine preservative thiomers ...

compounds; formed as intermediates in

oxymercuration reaction In organic chemistry, the oxymercuration reaction is an electrophilic addition reaction that transforms an alkene () into a neutral alcohol. In oxymercuration, the alkene reacts with mercuric acetate () in aqueous solution to yield the additio ...

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 triphenylm ...

, (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 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 a 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 for ...

)

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 (, ) was a Jewish collaborationist organization in the Warsaw Ghetto during the German occupation of Poland in World War II. The rise and fall of the Group was likely a proxy for power struggles between various facti ... (boron group) onium cations

Group 14 (carbon group) onium cations

Group 15 , - ! colspan=2 style="text-align:left;" , ↓ Period , - ! 2 , , - ! 3 , , - ! 4 , , - ! 5 , , - ! 6 , , - ! 7 , , - , colspan="2", ---- ''Legend'' A pnictogen ( or ; from "to choke" and -gen, "generator") is any ... (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 ... (chalcogen) onium cations

Hydrogen onium cation

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, inorgani ... onium cations

Group 18 (noble gas) onium cations

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 (, ) was a Jewish collaborationist organization in the Warsaw Ghetto during the German occupation of Poland in World War II. The rise and fall of the Group was likely a proxy for power struggles between various facti ...
(boron group) onium cations

Group 15 , - ! colspan=2 style="text-align:left;" , ↓ Period , - ! 2 , , - ! 3 , , - ! 4 , , - ! 5 , , - ! 6 , , - ! 7 , , - , colspan="2", ---- ''Legend'' A pnictogen ( or ; from "to choke" and -gen, "generator") is any ...
(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 ...
(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, inorgani ...
onium cations