Triatomic molecule

Short description: Molecules made of three atoms

Carbon dioxide

Triatomic molecules are molecules composed of three atoms, of either the same or different chemical elements. Examples include H2O, CO2 (pictured), HCN, O3 (ozone) and NO2.

## Contents

* 1 Molecular vibrations
* 1.1 Symmetric linear molecules
* 2 Types
* 2.1 Homonuclear
* 3 Geometry
* 3.1 Linear
* 3.2 Bent
* 3.3 Cyclic
* 4 References
* 5 External links

## Molecular vibrations

The vibrational modes of a triatomic molecule can be determined in specific cases.

### Symmetric linear molecules

A symmetric linear molecule ABA can perform:

* Antisymmetric longitudinal vibrations with frequency

ωa=k1MmAmB

* Symmetric longitudinal vibrations with frequency

ωs1=k1mA

* Symmetric transversal vibrations with frequency

ωs2=2k2MmAmB

In the previous formulas, M is the total mass of the molecule, mA and mB are the masses of the elements A and B, k1 and k2 are the spring constants of the molecule along its axis and perpendicular to it.

## Types

### Homonuclear

Ozone, O3 Trihydrogen cation, H3+

Homonuclear triatomic molecules contain three of the same kind of atom. That molecule will be an allotrope of that element.

Ozone, O3 is an example of a triatomic molecule with all atoms the same. Triatomic hydrogen, H3, is unstable and breaks up spontaneously. H3+, the trihydrogen cation is stable by itself and is symmetric. 4He3, the helium trimer is only weakly bound by van der Waals force and is in an Efimov state.[1] Trisulfur (S3) is analogous to ozone.

## Geometry

All triatomic molecules may be classified as possessing either a linear, bent, or cyclic geometry.Template:Expansion needed

### Linear

Linear triatomic molecules owe their geometry to their sp or sp3d hybridised central atoms. Well-known linear triatomic molecules include carbon dioxide (CO2) and hydrogen cyanide (HCN).

Xenon difluoride (XeF2) is one of the rare examples of a linear triatomic molecule possessing non-bonded pairs of electrons on the central atom.

### Bent

### Cyclic

## References

1. ↑ Kunitski, M.; Zeller, S.; Voigtsberger, J.; Kalinin, A.; Schmidt, L. P. H.; Schoffler, M.; Czasch, A.; Schollkopf, W. et al. (30 April 2015). "Observation of the Efimov state of the helium trimer". Science 348 (6234): 551–555. doi:10.1126/science.aaa5601. PMID 25931554. Bibcode: 2015Sci...348..551K.

## External links

* v
* t
* e

Molecules detected in outer space

Molecules|

| Diatomic|

* Aluminium monochloride
* Aluminium monofluoride
* Aluminium monoxide
* Argonium
* Carbon monophosphide
* Carbon monosulfide
* Carbon monoxide
* Carborundum
* Cyanogen radical
* Diatomic carbon
* Fluoromethylidynium
* Helium hydride ion
* Hydrogen chloride
* Hydrogen fluoride
* Hydrogen (molecular)
* Hydroxyl radical
* Iron(II) oxide
* Magnesium monohydride cation
* Methylidyne radical
* Nitric oxide
* Nitrogen (molecular)
* Nitrogen monohydride
* Nitrogen sulfide
* Oxygen (molecular)
* Phosphorus monoxide
* Phosphorus mononitride
* Potassium chloride
* Silicon carbide
* Silicon mononitride
* Silicon monoxide
* Silicon monosulfide
* Sodium chloride
* Sodium iodide
* Sulfur monohydride
* Sulfur monoxide
* Titanium oxide

|
|

Triatomic|

* Aluminium hydroxide
* Aluminium isocyanide
* Amino radical
* Carbon dioxide
* Carbonyl sulfide
* CCP radical
* Chloronium
* Diazenylium
* Dicarbon monoxide
* Disilicon carbide
* Ethynyl radical
* Formyl radical
* Hydrogen cyanide (HCN)
* Hydrogen isocyanide (HNC)
* Hydrogen sulfide
* Hydroperoxyl
* Iron cyanide
* Isoformyl
* Magnesium cyanide
* Magnesium isocyanide
* Methylene radical
* N2H+
* Nitrous oxide
* Nitroxyl
* Ozone
* Phosphaethyne
* Potassium cyanide
* Protonated molecular hydrogen
* Sodium cyanide
* Sodium hydroxide
* Silicon carbonitride
* c-Silicon dicarbide
* SiNC
* Sulfur dioxide
* Thioformyl
* Thioxoethenylidene
* Titanium dioxide
* Tricarbon
* Water

Four
atoms|

* Acetylene
* Ammonia
* Cyanic acid
* Cyanoethynyl
* Cyclopropynylidyne
* Formaldehyde
* Fulminic acid
* HCCN
* Hydrogen peroxide
* Hydromagnesium isocyanide
* Isocyanic acid
* Isothiocyanic acid
* Ketenyl
* Methylene amidogen
* Methyl radical
* Propynylidyne
* Protonated carbon dioxide
* Protonated hydrogen cyanide
* Silicon tricarbide
* Thioformaldehyde
* Tricarbon monoxide
* Tricarbon sulfide
* Thiocyanic acid

Five
atoms|

* Ammonium ion
* Butadiynyl
* Carbodiimide
* Cyanamide
* Cyanoacetylene
* Cyanoformaldehyde
* Cyanomethyl
* Cyclopropenylidene
* Formic acid
* Isocyanoacetylene
* Ketene
* Methane
* Methoxy radical
* Methylenimine
* Propadienylidene
* Protonated formaldehyde
* Protonated formaldehyde
* Silane
* Silicon-carbide cluster

Six
atoms|

* Acetonitrile
* Cyanobutadiynyl radical
* E-Cyanomethanimine
* Cyclopropenone
* Diacetylene
* Ethylene
* Formamide
* HC4N
* Ketenimine
* Methanethiol
* Methanol
* Methyl isocyanide
* Pentynylidyne
* Propynal
* Protonated cyanoacetylene

Seven
atoms|

* Acetaldehyde
* Acrylonitrile
* Vinyl cyanide
* Cyanodiacetylene
* Ethylene oxide
* Glycolonitrile
* Hexatriynyl radical
* Methylacetylene
* Methylamine
* Methyl isocyanate
* Vinyl alcohol

Eight
atoms|

* Acetic acid
* Aminoacetonitrile
* Cyanoallene
* Ethanimine
* Glycolaldehyde
* Heptatrienyl radical
* Hexapentaenylidene
* Methylcyanoacetylene
* Methyl formate
* Propenal

Nine
atoms|

* Acetamide
* Cyanohexatriyne
* Cyanotriacetylene
* Dimethyl ether
* Ethanol
* Methyldiacetylene
* Octatetraynyl radical
* Propene
* Propionitrile

Ten
atoms
or more|

* Acetone
* Benzene
* Benzonitrile
* Buckminsterfullerene (C60, C60+, fullerene, buckyball)
* C70 fullerene
* Cyanodecapentayne
* Cyanopentaacetylene
* Cyanotetra-acetylene
* Ethylene glycol
* Ethyl formate
* Methyl acetate
* Methyl-cyano-diacetylene
* Methyltriacetylene
* Propanal
* n-Propyl cyanide
* Pyrimidine

Deuterated
molecules|

* Ammonia
* Ammonium ion
* Formaldehyde
* Formyl radical
* Heavy water
* Hydrogen cyanide
* Hydrogen deuteride
* Hydrogen isocyanide
* Methylacetylene
* N2D+
* Trihydrogen cation

Unconfirmed|

* Anthracene
* Dihydroxyacetone
* Ethyl methyl ether
* Glycine
* Graphene
* H2NCO+
* Linear C5
* Naphthalene cation
* Phosphine
* Pyrene
* Silylidine

Related|

* Abiogenesis
* Astrobiology
* Astrochemistry
* Atomic and molecular astrophysics
* Chemical formula
* Circumstellar envelope
* Cosmic dust
* Cosmic ray
* Cosmochemistry
* Diffuse interstellar band
* Earliest known life forms
* Extraterrestrial life
* Extraterrestrial liquid water
* Forbidden mechanism
* Homochirality
* Intergalactic dust
* Interplanetary medium
* Interstellar medium
* Photodissociation region
* Iron–sulfur world theory
* Kerogen
* Molecules in stars
* Nexus for Exoplanet System Science
* Organic compound
* Outer space
* PAH world hypothesis
* Panspermia
* Polycyclic aromatic hydrocarbon (PAH)
* RNA world hypothesis
* Spectroscopy
* Tholin

* Category:Astrochemistry
*   *   *

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