Argon

• Formula: Ar
• Molecular weight: 39.948
• IUPAC Standard InChI: InChI=1S/Ar Copy

  
• IUPAC Standard InChIKey: XKRFYHLGVUSROY-UHFFFAOYSA-N Copy
• CAS Registry Number: 7440-37-1
• Chemical structure:
  This structure is also available as a 2d Mol file
• Other names: Ar; UN 1006; UN 1951; argon atom
• Permanent link for this species. Use this link for bookmarking this species for future reference.
• Information on this page:
  • Gas phase thermochemistry data
  • Phase change data
  • Reaction thermochemistry data (reactions 1 to 50)
  • Gas phase ion energetics data
  • References
  • Notes
• Other data available:
  • Reaction thermochemistry data: reactions 51 to 100, reactions 101 to 102
  • Henry's Law data
  • Ion clustering data
  • Mass spectrum (electron ionization)
  • Fluid Properties
• Data at other public NIST sites:
  • NIST Atomic Spectra Database - Lines Holdings (on physics web site)
  • NIST Atomic Spectra Database - Levels Holdings (on physics web site)
  • NIST Atomic Spectra Database - Ground states and ionization energies (on physics web site)
  • Gas Phase Kinetics Database
  • X-ray Photoelectron Spectroscopy Database, version 5.0
  • X-ray Photoelectron Spectroscopy Database, version 5.0
  • X-ray Photoelectron Spectroscopy Database, version 5.0
  • X-ray Photoelectron Spectroscopy Database, version 5.0
  • X-ray Photoelectron Spectroscopy Database, version 5.0
  • X-ray Photoelectron Spectroscopy Database, version 5.0
  • X-ray Photoelectron Spectroscopy Database, version 5.0
  • X-ray Photoelectron Spectroscopy Database, version 5.0
• Options:
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Data at NIST subscription sites:

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• NIST / TRC Web Thermo Tables, professional edition (thermophysical and thermochemical data)

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Gas phase thermochemistry data

Go To: Top, Phase change data, Reaction thermochemistry data, Gas phase ion energetics data, References, Notes

Data compilation copyright by the U.S. Secretary of Commerce on behalf of the U.S.A. All rights reserved.

Gas Phase Heat Capacity (Shomate Equation)

C_p° = A + B*t + C*t² + D*t³ + E/t²
H° − H°_298.15= A*t + B*t²/2 + C*t³/3 + D*t⁴/4 − E/t + F − H
S° = A*ln(t) + B*t + C*t²/2 + D*t³/3 − E/(2*t²) + G
    C_p = heat capacity (J/mol*K)
    H° = standard enthalpy (kJ/mol)
    S° = standard entropy (J/mol*K)
    t = temperature (K) / 1000.

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Phase change data

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Data compilation copyright by the U.S. Secretary of Commerce on behalf of the U.S.A. All rights reserved.

Data compiled as indicated in comments:
TRC - Thermodynamics Research Center, NIST Boulder Laboratories, Chris Muzny director

Antoine Equation Parameters

log₁₀(P) = A − (B / (T + C))
    P = vapor pressure (bar)
    T = temperature (K)

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Reaction thermochemistry data

Go To: Top, Gas phase thermochemistry data, Phase change data, Gas phase ion energetics data, References, Notes

Data compilation copyright by the U.S. Secretary of Commerce on behalf of the U.S.A. All rights reserved.

Data compiled as indicated in comments:
RCD - Robert C. Dunbar
M - Michael M. Meot-Ner (Mautner) and Sharon G. Lias
B - John E. Bartmess

Note: Please consider using the reaction search for this species. This page allows searching of all reactions involving this species. A general reaction search form is also available. Future versions of this site may rely on reaction search pages in place of the enumerated reaction displays seen below.

Reactions 1 to 50

 +  = ( • )

By formula: Li⁺ + Ar = (Li⁺ • Ar)

Free energy of reaction

Ar⁺ +  = (Ar⁺ • )

By formula: Ar⁺ + Ar = (Ar⁺ • Ar)

 +  = ( • )

By formula: K⁺ + Ar = (K⁺ • Ar)

 +  = ( • )

By formula: N₂⁺ + Ar = (N₂⁺ • Ar)

 +  = ( • )

By formula: Cs⁺ + Ar = (Cs⁺ • Ar)

 +  = ( • )

By formula: Cr⁺ + Ar = (Cr⁺ • Ar)

 +  = ( • )

By formula: Na⁺ + Ar = (Na⁺ • Ar)

H₃⁺ +  = (H₃⁺ • )

By formula: H₃⁺ + Ar = (H₃⁺ • Ar)

Xe⁺ +  = (Xe⁺ • )

By formula: Xe⁺ + Ar = (Xe⁺ • Ar)

(Ar⁺ • 2) +  = (Ar⁺ • 3)

By formula: (Ar⁺ • 2Ar) + Ar = (Ar⁺ • 3Ar)

Free energy of reaction

( • 7) +  = ( • 8)

By formula: (N₂⁺ • 7Ar) + Ar = (N₂⁺ • 8Ar)

( • 8) +  = ( • 9)

By formula: (N₂⁺ • 8Ar) + Ar = (N₂⁺ • 9Ar)

 +  = ArF^-

By formula: F^- + Ar = ArF^-

 +  = ( • )

By formula: Rb⁺ + Ar = (Rb⁺ • Ar)

(O^- • 10) +  = (O^- • 11)

By formula: (O^- • 10Ar) + Ar = (O^- • 11Ar)

(O^- • 11) +  = (O^- • 12)

By formula: (O^- • 11Ar) + Ar = (O^- • 12Ar)

(O^- • 12) +  = (O^- • 13)

By formula: (O^- • 12Ar) + Ar = (O^- • 13Ar)

(O^- • 13) +  = (O^- • 14)

By formula: (O^- • 13Ar) + Ar = (O^- • 14Ar)

(O^- • 14) +  = (O^- • 15)

By formula: (O^- • 14Ar) + Ar = (O^- • 15Ar)

(O^- • 15) +  = (O^- • 16)

By formula: (O^- • 15Ar) + Ar = (O^- • 16Ar)

(O^- • 16) +  = (O^- • 17)

By formula: (O^- • 16Ar) + Ar = (O^- • 17Ar)

(O^- • 17) +  = (O^- • 18)

By formula: (O^- • 17Ar) + Ar = (O^- • 18Ar)

(O^- • 18) +  = (O^- • 19)

By formula: (O^- • 18Ar) + Ar = (O^- • 19Ar)

(O^- • 19) +  = (O^- • 20)

By formula: (O^- • 19Ar) + Ar = (O^- • 20Ar)

(O^- • 20) +  = (O^- • 21)

By formula: (O^- • 20Ar) + Ar = (O^- • 21Ar)

(O^- • 21) +  = (O^- • 22)

By formula: (O^- • 21Ar) + Ar = (O^- • 22Ar)

(O^- • 22) +  = (O^- • 23)

By formula: (O^- • 22Ar) + Ar = (O^- • 23Ar)

(O^- • 23) +  = (O^- • 24)

By formula: (O^- • 23Ar) + Ar = (O^- • 24Ar)

(O^- • 24) +  = (O^- • 25)

By formula: (O^- • 24Ar) + Ar = (O^- • 25Ar)

(O^- • 25) +  = (O^- • 26)

By formula: (O^- • 25Ar) + Ar = (O^- • 26Ar)

(O^- • 9) +  = (O^- • 10)

By formula: (O^- • 9Ar) + Ar = (O^- • 10Ar)

(O^- • 2) +  = (O^- • 3)

By formula: (O^- • 2Ar) + Ar = (O^- • 3Ar)

(O^- • 3) +  = (O^- • 4)

By formula: (O^- • 3Ar) + Ar = (O^- • 4Ar)

(O^- • 4) +  = (O^- • 5)

By formula: (O^- • 4Ar) + Ar = (O^- • 5Ar)

(O^- • 5) +  = (O^- • 6)

By formula: (O^- • 5Ar) + Ar = (O^- • 6Ar)

(O^- • 6) +  = (O^- • 7)

By formula: (O^- • 6Ar) + Ar = (O^- • 7Ar)

(O^- • 7) +  = (O^- • 8)

By formula: (O^- • 7Ar) + Ar = (O^- • 8Ar)

(O^- • 8) +  = (O^- • 9)

By formula: (O^- • 8Ar) + Ar = (O^- • 9Ar)

(O^- • ) +  = (O^- • 2)

By formula: (O^- • Ar) + Ar = (O^- • 2Ar)

(Ar⁺ • ) +  = (Ar⁺ • 2)

By formula: (Ar⁺ • Ar) + Ar = (Ar⁺ • 2Ar)

( • ) +  = ( • 2)

By formula: (N₂⁺ • Ar) + Ar = (N₂⁺ • 2Ar)

O^- +  = (O^- • )

By formula: O^- + Ar = (O^- • Ar)

(Ar⁺ • 10) +  = (Ar⁺ • 11)

By formula: (Ar⁺ • 10Ar) + Ar = (Ar⁺ • 11Ar)

(Ar⁺ • 9) +  = (Ar⁺ • 10)

By formula: (Ar⁺ • 9Ar) + Ar = (Ar⁺ • 10Ar)

(D₃⁺ • 2) +  = (D₃⁺ • 3)

By formula: (D₃⁺ • 2Ar) + Ar = (D₃⁺ • 3Ar)

(D₃⁺ • 3) +  = (D₃⁺ • 4)

By formula: (D₃⁺ • 3Ar) + Ar = (D₃⁺ • 4Ar)

(D₃⁺ • 4) +  = (D₃⁺ • 5)

By formula: (D₃⁺ • 4Ar) + Ar = (D₃⁺ • 5Ar)

(D₃⁺ • 5) +  = (D₃⁺ • 6)

By formula: (D₃⁺ • 5Ar) + Ar = (D₃⁺ • 6Ar)

(D₃⁺ • 6) +  = (D₃⁺ • 7)

By formula: (D₃⁺ • 6Ar) + Ar = (D₃⁺ • 7Ar)

(Ar⁺ • 3) +  = (Ar⁺ • 4)

By formula: (Ar⁺ • 3Ar) + Ar = (Ar⁺ • 4Ar)

Gas phase ion energetics data

Go To: Top, Gas phase thermochemistry data, Phase change data, Reaction thermochemistry data, References, Notes

Data compilation copyright by the U.S. Secretary of Commerce on behalf of the U.S.A. All rights reserved.

Data evaluated as indicated in comments:
HL - Edward P. Hunter and Sharon G. Lias
L - Sharon G. Lias

Data compiled as indicated in comments:
LL - Sharon G. Lias and Joel F. Liebman
LBLHLM - Sharon G. Lias, John E. Bartmess, Joel F. Liebman, John L. Holmes, Rhoda D. Levin, and W. Gary Mallard
LLK - Sharon G. Lias, Rhoda D. Levin, and Sherif A. Kafafi
RDSH - Henry M. Rosenstock, Keith Draxl, Bruce W. Steiner, and John T. Herron

Ionization energy determinations

References

Go To: Top, Gas phase thermochemistry data, Phase change data, Reaction thermochemistry data, Gas phase ion energetics data, Notes

Data compilation copyright by the U.S. Secretary of Commerce on behalf of the U.S.A. All rights reserved.

Cox, Wagman, et al., 1984
Cox, J.D.; Wagman, D.D.; Medvedev, V.A., CODATA Key Values for Thermodynamics, Hemisphere Publishing Corp., New York, 1984, 1. [all data]

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Streng, A.G., Miscibility and Compatibility of Some Liquid and Solidified Gases at Low Temperature, J. Chem. Eng. Data, 1971, 16, 357. [all data]

Gosman, McCarty, et al., 1969
Gosman, A.L.; McCarty, R.D.; Hust, J.G., Thermodynamic Properties of Argon from the Triple Point to 300 K at Pressures to 1000 Atmospheres, Nat. Stand. Ref. Data Ser., Nat. Bur. Stand. NSRDS-NBS 27, 1969. [all data]

Van't Zelfde, Omar, et al., 1968
Van't Zelfde, P.; Omar, M.H.; LePair-Schroten, H.G.M.; Dokoupil, Z., Solid-liquid equilibrium diagram for the argon + methane system., Physica (Amsterdam), 1968, 38, 241-51. [all data]

Angus, Armstrong, et al., 1972
Angus, S.; Armstrong, B.; Gosman, A.L.; McCarty, R.D.; Hust, J.G.; Vasserman, A.A.; Rabinovich, V.A., International Thermodynamic Tables of the Fluid State - 1 Argon, Butterworths, London, 1972. [all data]

Ziegler, Mullins, et al., 1962
Ziegler, W.T.; Mullins, J.C.; Kirk, B.S., Calculation of the Vapor Pressure and Heats of Vaporization and Sublimation of Liquids and Solids, Especially Below One Atmosphere Pressure. II. Argon, Ga. Inst. Technol., Eng. Exp. Stn., Proj. A-460, Tech. Rep. No. 2, 1962. [all data]

Clark, Din, et al., 1951
Clark, A.M.; Din, F.; Robb, J.; Michels, A.; Wassenaar, T.; Zwietering, Th.N., The Vapor Pressure of Argon, Physica (Amsterdam), 1951, 17, 876. [all data]

Clusius and Weigand, 1940
Clusius, K.; Weigand, K., Melting Curves of the Gases A, Kr, Xe, CH4, CH3D, CD4, C2H4, C2H6, COS, and PH3 to 200 Atmospheres Pressure. The Chane of Volume on Melting, Z. Phys. Chem., Abt. B, 1940, 46, 1-37. [all data]

McCain and Ziegler, 1967
McCain, W.D., Jr.; Ziegler, W.T., The Critical Temperature, Critical Pressure, and Vapor Pressure of Argon, J. Chem. Eng. Data, 1967, 12, 2, 199-202, https://doi.org/10.1021/je60033a012 . [all data]

Drii and Rabinovich, 1966
Drii, L.I.; Rabinovich, V.A., Dependence of Vapor Pressure of Argon, Zh. Fiz. Khim., 1966, 40, 709-711. [all data]

van Itterbeek, Verbeke, et al., 1963
van Itterbeek, A.; Verbeke, O.; Staes, K., Measurements on the Equation of State of Liquid Argon and Methane Up to 300 kg cm^-2 at Low Temperatures, Physica (Amsterdam), 1963, 29, 6, 742-754, https://doi.org/10.1016/S0031-8914(63)80231-1 . [all data]

Clark, Din, et al., 1951, 2
Clark, A.M.; Din, F.; Robb, J.; Michels, A.; Wassenaar, T.; Zwietering, Th., The Vapour Pressure of Argon, Physica (Amsterdam), 1951, 17, 10, 876-884, https://doi.org/10.1016/0031-8914(51)90041-9 . [all data]

McKnight and Sawina, 1973
McKnight, L.G.; Sawina, J.M., Equilibrium Constants and Binding Energies of Alkali Metal Ions with Inert Gases, Bull. Am. Phys. Soc., 1973, 18, 804. [all data]

Cassidy and Elford, 1985
Cassidy, R.A.; Elford, M.T., The Mobility of Li+ Ions in Helium and Argon, Aust. J. Phys., 1985, 38, 4, 587, https://doi.org/10.1071/PH850587 . [all data]

Keller, Beyer, et al., 1973
Keller, C.E.; Beyer, R.A.; Colonna-Romano, L.M., Clustering of Ar to Li+ and a Comparison of Drift - Tube Models, Phys. Rev. A, 1973, 8, 3, 1446, https://doi.org/10.1103/PhysRevA.8.1446 . [all data]

Teng and Conway, 1973
Teng, H.H.; Conway, D.C., Ion - Molecule Equilibria in Mixtures of N2 and Ar, J. Chem. Phys., 1973, 59, 5, 2316, https://doi.org/10.1063/1.1680338 . [all data]

Turner and Conway, 1979
Turner, D.L.; Conway, D.C., Study of the 2Ar + Ar2+ = Ar + Ar3+ Reaction, J. Chem. Phys., 1979, 71, 4, 1899, https://doi.org/10.1063/1.438544 . [all data]

Liu and Conway, 1975
Liu, W.F.; Conway, D.C., Ion - Molecule Reactions in Ar at 296, 195, and 77 K, J. Chem. Phys., 1975, 62, 8, 3070, https://doi.org/10.1063/1.430906 . [all data]

Kim and Bowers, 1990
Kim, H.S.; Bowers, M.T., Energetics, Structure and Photodissociation Dynamics of the Cluster Ar.N2+, J. Chem. Phys., 1990, 93, 2, 1158, https://doi.org/10.1063/1.459179 . [all data]

Hiraoka and Nakajima, 1988
Hiraoka, K.; Nakajima, G., A Determination of the Stabilities of N2+(N2)n and O2+(N2)n with n = 1 - 11 from Measurements of the Gas - Phase Ion Equilibria, J. Chem. Phys., 1988, 88, 12, 7709, https://doi.org/10.1063/1.454285 . [all data]

Gatland, 1984
Gatland, I.R., Swarms of Ions and Electrons in Gases, W. Lindinger, T. D. Mark and F. Howorka, eds. (Springer, New York, 1984, 1984, 44. [all data]

Gislason, 1984
Gislason, E.A., Quoted in I. R. Gatland in Swarms of Ions and Electrons in Gases, W. Lindinger, T. D. Mark and F. Howorka, eds. (Springer, New York, 1984, 1984, 44. [all data]

Viehland, 1984
Viehland, L.A., Interaction Potentials for Li+ - Rare - Gas Systems, Chem. Phys., 1984, 78, 2, 279, https://doi.org/10.1016/0301-0104(83)85114-3 . [all data]

Takebe, 1983
Takebe, M., The Generalized Mobility Curve for Alkali Ions in Rare Gases: Clustering Reactions and Mobility Curves, J. Chem. Phys., 1983, 78, 12, 7223, https://doi.org/10.1063/1.444763 . [all data]

Kemper, Hsu, et al., 1991
Kemper, P.R.; Hsu, M.T.; Bowers, M.T., Transition - Metal Ion - Rare Gas Clusters: Bond Strengths and Molecular Parameters for Co+(He/Ne)n, Ni+(He/Ne)n, and Cr+(He/Ne/Ar), J. Phys. Chem., 1991, 95, 26, 10600, https://doi.org/10.1021/j100179a022 . [all data]

Armentrout and Rodgers, 2000
Armentrout, P.B.; Rodgers, M.T., An Absolute Sodium Cation Affinity Scale: Threshold Collision-Induced Dissociation Experiments and ab Initio Theory, J. Phys. Chem A, 2000, 104, 11, 2238, https://doi.org/10.1021/jp991716n . [all data]

Hiraoka and Mori, 1989
Hiraoka, K.; Mori, T., Isotope Effect and Nature of Bonding in the Cluster Ions H3+(Ar)n and D3+(Ar)n, J. Chem. Phys., 1989, 91, 8, 4821, https://doi.org/10.1063/1.456720 . [all data]

Bedford and Smith, 1990
Bedford, D.K.; Smith, D., Variable-temperature selected ion flow tube studies of the reactions of Ar+, Ar2+ and ArHn+ (n=1-3) ions with H2, HD and D2 at 300 K and 80 K, Int. J. Mass Spectrom. Ion Proc., 1990, 98, 2, 179, https://doi.org/10.1016/0168-1176(90)85017-V . [all data]

Dehmer and Pratt, 1982
Dehmer, P.M.; Pratt, S.T., Photoionization of ArKr, ArXe, and KrXe and bond dissociation energies of the rare gas dimer ions, J. Chem. Phys., 1982, 77, 4804. [all data]

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Jones, J.D.C.; Lister, D.G.; Twiddy, N.D., Equilibrium Constant for the Reaction Xe+ + 2Ar ---> XeAr+ + Ar in the Temperature Range 150 - 300 K and the Dissociation Energy of XeAr+, Chem. Phys. Lett., 1980, 70, 3, 575, https://doi.org/10.1016/0009-2614(80)80128-X . [all data]

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Ng, C.Y.; Tiedemann, P.W.; Mahan, B.H.; Lee, Y.T., Photoionization Studies of the Diatomic Internuclear Rare Gas Molecules XeKr, XeAr, and KrAr, J. Chem. Phys., 1977, 66, 12, 5737, https://doi.org/10.1063/1.433848 . [all data]

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Hiraoka, Mori, et al., 1992
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Notes

Go To: Top, Gas phase thermochemistry data, Phase change data, Reaction thermochemistry data, Gas phase ion energetics data, References

• Symbols used in this document:
  

  IE (evaluated)	Recommended ionization energy
  Pc	Critical pressure
  Ptriple	Triple point pressure
  S°gas,1 bar	Entropy of gas at standard conditions (1 bar)
  T	Temperature
  Tboil	Boiling point
  Tc	Critical temperature
  Tfus	Fusion (melting) point
  Ttriple	Triple point temperature
  ΔrG°	Free energy of reaction at standard conditions
  ΔrH°	Enthalpy of reaction at standard conditions
  ΔrS°	Entropy of reaction at standard conditions
  ρc	Critical density

• Data from NIST Standard Reference Database 69: NIST Chemistry WebBook
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