List of Molecules and Ions with 2 to 10 Atoms

Diatomic (44) Molecule Designation Mass Ions AlCl Aluminium monochloride [39] [40] 62.5 — AlF Aluminium monofluoride [39] [41] 46 — AlO Aluminium monoxide [42] 43 — — Argonium [43] [44] 41 ArH+

C2 Diatomic carbon [45] [46] 24 — — Fluoromethylidynium 31 CF+[47] CH Methylidyne radical [32] [48] 13 CH+[49] CN Cyanogen radical [39] [48] [50] [51] 26 CN+,[52] CN−[53] CO Carbon monoxide [39] [54] [55] 28 CO+[56] CP Carbon monophosphide [51] 43 — CS Carbon monosulfide [39] 44 — FeO Iron(II) oxide [57] 82 — — Helium hydride ion [58] [59] 5 HeH+

H2 Molecular hydrogen [60] 2 — HCl Hydrogen chloride [61] 36.5 HCl+[62] HF Hydrogen fluoride [63] 20 — HO Hydroxyl radical [39] 17 OH+[64] KCl Potassium chloride [39] [40] 75.5 — NH Nitrogen monohydride [65] [66] 15 —

N2 Molecular nitrogen [67] [68] 28 — NO Nitric oxide [69] 30 NO+[52] NS Nitrogen sulfide [39] 46 — NaCl Sodium chloride [39] [40] 58.5 — — Magnesium monohydride cation 25.3 MgH+[52] NaI Sodium iodide [70] 150 —

O2 Molecular oxygen [71] 32 — PN Phosphorus mononitride [72] 45 — PO Phosphorus monoxide [73] 47 — SH Sulfur monohydride [74] 33 SH+[75] SO Sulfur monoxide [39] 48 SO+[49] SiC Carborundum [39] [76] 40 — SiN Silicon mononitride [39] 42 — SiO Silicon monoxide [39] 44 — Molecule Designation Mass Ions SiS Silicon monosulfide [39] 60 — TiO Titanium oxide [77] 63.9 —

The H+ 3 cation is one of the most abundant ions in the universe. It was first detected in 1993. [78] [79]

Triatomic (41) Molecule Designation Mass Ions AlNC Aluminium isocyanide [39] 53 — AlOH Aluminium hydroxide [80] 44 —

C3 Tricarbon [81] [82] 36 —

C2H Ethynyl radical [39] [50] 25 — CCN Cyanomethylidyne [83] 38 —

C2O Dicarbon monoxide [84] 40 —

C2S Thioxoethenylidene [85] 56 —

C2P —[86] 55 —

CO2 Carbon dioxide [87] 44 — FeCN Iron cyanide [88] 82 — H+ — Protonated molecular hydrogen 3 3 [78] [79]

H2C Methylene radical [89] 14 — + — Chloronium 37.5 H2Cl [90] + H2O Water [91] 18 H2O [92]

HO2 Hydroperoxyl [93] 33 —

H2S Hydrogen sulfide [39] 34 — HCN Hydrogen cyanide [39] [50] [94] 27 — HNC Hydrogen isocyanide [95] [96] 27 — HCO Formyl radical [97] 29 HCO+ [49] [97] [98] HCP Phosphaethyne [99] 44 — Molecule Designation Mass Ions HCS Thioformyl [100] 45 HCS+ [49] [98] HN+ — Diazenylium [98] [49] [101] 29 2 HNO Nitroxyl [102] 31 — — Isoformyl 29 HOC+[50] HSC Isothioformyl [100] 45 — KCN Potassium cyanide [39] 65 — MgCN Magnesium cyanide [39] 50 — MgNC Magnesium isocyanide [39] 50 —

NH2 Amino radical[103] 16 —

N2O Nitrous oxide [104] 44 — NaCN Sodium cyanide [39] 49 — NaOH Sodium hydroxide [105] 40 — OCS Carbonyl sulfide [106] 60 —

O3 Ozone [107] 48 —

SO2 Sulfur dioxide [39] [108] 64 —

c-SiC2 c- Silicon dicarbide [39] [76] 52 — SiCSi Disilicon carbide [109] 68 — SiCN Silicon carbonitride [110] 54 — SiNC [111] 54 —

TiO2 Titanium dioxide [77] 79.9 —

Formaldehyde is an organic molecule that is widely distributed in the interstellar medium.[112]

Four atoms (28) Molecule Designation Mass Ions

CH3 Methyl radical [113] 15 — + l-C3H Propynylidyne [39] [114] 37 l-C3H [115] Molecule Designation Mass Ions

c-C3H Cyclopropynylidyne [116] 37 — − C3N Cyanoethynyl [117] 50 C3N [118]

C3O Tricarbon monoxide [114] 52 —

C3S Tricarbon sulfide [39] [85] 68 — + — Hydronium 19 H3O [119]

C2H2 Acetylene [120] 26 — + H2CN Methylene amidogen [121] 28 H2CN [49]

H2CO Formaldehyde [112] 30 —

H2CS Thioformaldehyde [122] 46 — HCCN —[123] 39 — HCCO Ketenyl [124] 41 — — Protonated hydrogen cyanide 28 HCNH + [98] — Protonated carbon dioxide 45 HOCO+[125] HCNO Fulminic acid [126] 43 — HOCN Cyanic acid [127] 43 — CNCN Isocyanogen [128] 52 — HOOH Hydrogen peroxide [129] 34 — HNCO Isocyanic acid [108] 43 — HNCS Isothiocyanic acid [130] 59 —

NH3 Ammonia [39] [131] 17 — HSCN Thiocyanic acid [132] 59 —

SiC3 Silicon tricarbide [39] 64 — HMgNC Hydromagnesium isocyanide [133] 51.3 —

HNO2 Nitrous acid [134] 47 —

Methane, the primary component of natural gas, has also been detected on comets and in the atmosphere of several planets in the Solar System.[135] Five atoms (20) Molecule Designation Mass Ions NH+ — Ammonium ion [136] [137] 18 4

CH4 Methane [138] 16 —

CH3O Methoxy radical [139] 31 —

c-C3H2 Cyclopropenylidene [50] [140] [141] 38 —

l-H2C3 Propadienylidene [141] 38 —

H2CCN Cyanomethyl [142] 40 —

H2C2O Ketene [108] 42 —

H2CNH Methylenimine [143] 29 — HNCNH Carbodiimide [144] 42 — + — Protonated formaldehyde 31 H2COH [145] − C4H Butadiynyl [39] 49 C4H [146]

HC3N Cyanoacetylene [39] [50] [98] [147] [148] 51 — HCC-NC Isocyanoacetylene [149] 51 — HCOOH Formic acid [150] [147] 46 —

NH2CN Cyanamide [151] 42 — — Protonated cyanogen 53 NCCNH+[152] HC(O)CN Cyanoformaldehyde[153] 55 —

C5 Linear C5[154] 60 —

SiC4 Silicon-carbide cluster[76] 92 —

SiH4 Silane [155] 32 —

In the ISM, formamide (above) can combine with methylene to form acetamide.[156] Six atoms (16) Molecule Designation Mass Ions

c-H2C3O Cyclopropenone [157] 54 — E-HNCHCN E- Cyanomethanimine [158] 54 —

C2H4 Ethylene [159] 28 —

CH3CN Acetonitrile [108] [160] [161] 40 —

CH3NC Methyl isocyanide [160] 40 —

CH3OH Methanol [108] [162] 32 —

CH3SH Methanethiol [163] 48 —

l-H2C4 Diacetylene [39] [164] 50 — + — Protonated cyanoacetylene 52 HC3NH [98]

HCONH2 Formamide [156] 44 —

C5H Pentynylidyne [39] [85] 61 —

C5N Cyanobutadiynyl radical [165] 74 —

HC2CHO Propynal [166] 54 —

HC4N —[39] 63 —

CH2CNH Ketenimine [140] 40 —

C5S —[167] 92 —

Acetaldehyde (above) and its isomers vinyl alcohol and ethylene oxide have all been detected in interstellar space.[168]

Seven atoms (11) Molecule Designation Mass Ions

c-C2H4O Ethylene oxide [169] 44 —

CH3C2H Methylacetylene [50] 40 —

H3CNH2 Methylamine [170] 31 — Molecule Designation Mass Ions

CH2CHCN Acrylonitrile [108] [160] 53 —

H2CHCOH Vinyl alcohol [168] 44 — − C6H Hexatriynyl radical [39] [85] 73 C6H [141] [171]

HC4CN Cyanodiacetylene [108] [148] [160] 75 —

HC5O —[172] 77 —

CH3CHO Acetaldehyde [39] [169] 44 —

CH3NCO Methyl isocyanate [173] 57 —

HOCH2CN Glycolonitrile [174] 57 —

The radio signature of acetic acid, a compound found in vinegar, was confirmed in 1997.[175]

Eight atoms (11) Molecule Designation Mass

H3CC2CN Methylcyanoacetylene [176] 65

H2COHCHO Glycolaldehyde [177] 60

HCOOCH3 Methyl formate [108] [147] [177] 60

CH3COOH Acetic acid [175] 60

H2C6 Hexapentaenylidene [39] [164] 74

CH2CHCHO Propenal [140] 56

CH2CCHCN Cyanoallene [140] [176] 65

CH3CHNH Ethanimine [178] 43

C7H Heptatrienyl radical[179] 85

NH2CH2CN Aminoacetonitrile [180] 56

(NH2)2CO Urea [181] 60

Nine atoms (10) Molecule Designation Mass Ions

CH3C4H Methyldiacetylene [182] 64 — Molecule Designation Mass Ions

CH3OCH3 Dimethyl Ether [183] 46 —

CH3CH2CN Propionitrile [39] [108] [160] 55 —

CH3CONH2 Acetamide [140] [156] 59 —

CH3CH2OH Ethanol [184] 46 — − C8H Octatetraynyl radical [185] 97 C8H [186] [187]

HC7N Cyanohexatriyne or Cyanotriacetylene [39] [131] [188] [189] 99 —

CH3CHCH2 Propylene (propene) [190] 42 —

CH3CH2SH Ethyl mercaptan [191] 62 —

A number of polyyne-derived chemicals are among the heaviest molecules found in the interstellar medium.

Ten or more atoms (17) Atoms Molecule Designation Mass Ions

10 (CH3)2CO Acetone [108] [192] 58 —

10 (CH2OH)2 Ethylene glycol [193] [194] 62 —

10 CH3CH2CHO Propanal [140] 58 —

10 CH3OCH2OH Methoxymethanol [195] 62 —

10 CH3C5N Methylcyanodiacetylene [140] 89 —

10 CH3CHCH2O Propylene oxide [196] 58 —

11 HC8CN Cyanotetraacetylene [39] [188] 123 —

11 C2H5OCHO Ethyl formate [197] 74 —

11 CH3COOCH3 Methyl acetate [198] 74 — Atoms Molecule Designation Mass Ions

11 CH3C6H Methyltriacetylene [140] [182] 88 —

12 C6H6 Benzene [164] 78 —

12 C3H7CN n -Propyl cyanide [197] 69 —

12 (CH3)2CHCN iso -Propyl cyanide [199] [200] 69 — C 13 6H Benzonitrile [201] 104 — 5CN

13 HC10CN Cyanopentaacetylene [188] 147 — Buckminsterfullerene C+ 60 C60 720 (C60 fullerene) [202] 60 [14] [15] [203] [204]

70 C70 C70 fullerene [202] 840 — Deuterated molecules (20) These molecules all contain one or more deuterium atoms, a heavier isotope of hydrogen. Atoms Molecule Designation 2 HD Hydrogen deuteride [205] [206] H D+, HD+ 3 2 Trihydrogen cation [205] [206] 2

3 HDO, D2O Heavy water [207] [208] 3 DCN Hydrogen cyanide [209] 3 DCO Formyl radical [209] 3 DNC Hydrogen isocyanide [209] + 3 N2D —[209]

4 NH2D, NHD2, ND3 Ammonia [206] [210] [211]

4 HDCO, D2CO Formaldehyde [206] [212] 4 DNCO Isocyanic acid [213] + 5 NH3D Ammonium ion [214] [215] NH 6 Formamide [213] 2CDO; NHDCHO

7 CH2DCCH, CH3CCD Methylacetylene [216] [217] Unconfirmed (12) Evidence for the existence of the following molecules has been reported in the scientific literature, but the detections are either described as tentative by the authors, or have been challenged by other researchers. They await independent confirmation. Atoms Molecule Designation 2 SiH Silylidine [95] Atoms Molecule Designation

4 PH3 Phosphine [218] 4 MgCCH Magnesium monoacetylide [167] 4 NCCP Cyanophosphaethyne [167] + 5 H2NCO —[219]

4 SiH3CN Silyl cyanide [167]

10 H2NCH2COOH Glycine [220] [221]

12 CO(CH2OH)2 Dihydroxyacetone [222]

12 C2H5OCH3 Ethyl methyl ether [223] C 18 10H+ Naphthalene cation[224] 8

24 C24 Graphene [225]

24 C14H10 Anthracene [10] [226]

26 C16H10 Pyrene [10] See also