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
  • Mass spectrum (electron ionization)
  • References
  • Notes
• Other data available:
  • Reaction thermochemistry data: reactions 51 to 100, reactions 101 to 102
  • Henry's Law data
  • Ion clustering data
  • 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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Gas phase thermochemistry data

Go To: Top, Phase change data, Reaction thermochemistry data, Gas phase ion energetics data, Mass spectrum (electron ionization), 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 (cal/mol*K)
    H° = standard enthalpy (kcal/mol)
    S° = standard entropy (cal/mol*K)
    t = temperature (K) / 1000.

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Phase change data

Go To: Top, Gas phase thermochemistry data, Reaction thermochemistry data, Gas phase ion energetics data, Mass spectrum (electron ionization), 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:
TRC - Thermodynamics Research Center, NIST Boulder Laboratories, Chris Muzny director

Antoine Equation Parameters

log₁₀(P) = A − (B / (T + C))
    P = vapor pressure (atm)
    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, Mass spectrum (electron ionization), 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, Mass spectrum (electron ionization), 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

Mass spectrum (electron ionization)

Go To: Top, Gas phase thermochemistry data, 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.

Data compiled by: NIST Mass Spectrometry Data Center, William E. Wallace, director

Spectrum

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Additional Data

References

Go To: Top, Gas phase thermochemistry data, Phase change data, Reaction thermochemistry data, Gas phase ion energetics data, Mass spectrum (electron ionization), Notes

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

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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]

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van Itterbeek, Verbeke, et al., 1963
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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]

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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]

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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]

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Gatland, 1984
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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]

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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]

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Winters, R.E.; Collins, J.H.; Courchene, W.L., Resolution of fine structure in ionization-efficiency curves, J. Chem. Phys., 1966, 45, 1931. [all data]

Al-Joboury and Turner, 1963
Al-Joboury, M.I.; Turner, D.W., Molecular photo-electron spectroscopy. Part I. The hydrogen and nitrogen molecules, J. Chem. Soc., 1963, 5141. [all data]

Notes

Go To: Top, Gas phase thermochemistry data, Phase change data, Reaction thermochemistry data, Gas phase ion energetics data, Mass spectrum (electron ionization), 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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