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
  • Reaction thermochemistry data (reactions 1 to 50)
  • Gas phase ion energetics data
  • References
  • Notes
• Other data available:
  • Phase change data
  • 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
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Gas phase thermochemistry 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.

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 (cal/mol*K)
    H° = standard enthalpy (kcal/mol)
    S° = standard entropy (cal/mol*K)
    t = temperature (K) / 1000.

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Reaction thermochemistry 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:
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, 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, 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]

Chase, 1998
Chase, M.W., Jr., NIST-JANAF Themochemical Tables, Fourth Edition, J. Phys. Chem. Ref. Data, Monograph 9, 1998, 1-1951. [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]

Jones, Lister, et al., 1980
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]

Ng, Tiedemann, et al., 1977
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]

Hiraoka and Mori, 1989, 2
Hiraoka, K.; Mori, T., Formation and Stabilities of Cluster Ions Arn+, J. Chem. Phys., 1989, 90, 12, 7143, https://doi.org/10.1063/1.456245 . [all data]

Hiraoka, Mori, et al., 1992
Hiraoka, K.; Mori, T.; Yamabe, S., Gas-Phase Solvation of N2+ with Ar Atoms - A Charge Switch in the Reaction N2+(Ar)...Ar+(N2), Chem. Phys. Lett., 1992, 189, 1, 7, https://doi.org/10.1016/0009-2614(92)85144-Y . [all data]

Wada, Kikkawa, et al., 2007
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Arnold, S.T.; Hendricks, J.H.; Bowen, K.H., Photoelectron spectroscopy of the solvated anion clusters O-(Ar)(n=1-26,34): Energetics and structure, J. Chem. Phys., 1995, 102, 1, 39, https://doi.org/10.1063/1.469415 . [all data]

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Notes

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

• Symbols used in this document:
  

  IE (evaluated)	Recommended ionization energy
  S°gas,1 bar	Entropy of gas at standard conditions (1 bar)
  T	Temperature
  ΔrG°	Free energy of reaction at standard conditions
  ΔrH°	Enthalpy of reaction at standard conditions
  ΔrS°	Entropy of reaction at standard conditions

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