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
  • Henry's Law data
  • Gas phase ion energetics data
  • References
  • Notes
• Other data available:
  • Reaction thermochemistry data: reactions 1 to 50, reactions 51 to 100, reactions 101 to 102
  • 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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• 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, Henry's Law 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 (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

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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 (atm)
    T = temperature (K)

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Henry's Law 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 by: Rolf Sander

Henry's Law constant (water solution)

k_H(T) = k°_H exp(d(ln(k_H))/d(1/T) ((1/T) - 1/(298.15 K)))
k°_H = Henry's law constant for solubility in water at 298.15 K (mol/(kg*bar))
d(ln(k_H))/d(1/T) = Temperature dependence constant (K)

Gas phase ion energetics data

Go To: Top, Gas phase thermochemistry data, Phase change data, Henry's Law 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, Henry's Law 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]

Streng, 1971
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]

Hunter and Lias, 1998
Hunter, E.P.; Lias, S.G., Evaluated Gas Phase Basicities and Proton Affinities of Molecules: An Update, J. Phys. Chem. Ref. Data, 1998, 27, 3, 413-656, https://doi.org/10.1063/1.556018 . [all data]

Weitzel, Mahnert, et al., 1994
Weitzel, K.-M.; Mahnert, J.; Penno, M., ZEKE-PEPICO investigations of dissociation energies in ionic reactions, Chem. Phys. Lett., 1994, 224, 371. [all data]

Lide, 1992
Lide, D.R. (Editor), Ionization potentials of atoms and atomic ions in Handbook of Chem. and Phys., 1992, 10-211. [all data]

Wetzel, Baiocchi, et al., 1987
Wetzel, R.C.; Baiocchi, F.A.; Hayes, T.R.; Freund, R.S., Absolute cross sections for electron-impact ionization of the rare-gas atoms by the fast-neutral-beam method, Phys. Rev. A, 1987, 35, 559. [all data]

Kelly, 1987
Kelly, R.L., Atomic and ionic spectrum lines of hydrogen through kryton, J. Phys. Chem. Ref. Data, 1987, 16. [all data]

Kimura, Katsumata, et al., 1981
Kimura, K.; Katsumata, S.; Achiba, Y.; Yamazaki, T.; Iwata, S., Ionization energies, Ab initio assignments, and valence electronic structure for 200 molecules in Handbook of HeI Photoelectron Spectra of Fundamental Organic Compounds, Japan Scientific Soc. Press, Tokyo, 1981. [all data]

Clare and Sowerby, 1981
Clare, P.; Sowerby, D.B., Electron impact ionisation energies of some halo-cyclotriphosphazenes, J. Inorg. Nucl. Chem., 1981, 43, 477. [all data]

Freiser, 1980
Freiser, B.S., Electron impact ionization of argon ions by trapped ion cyclotron resonanace spectroscopy, Int. J. Mass Spectrom. Ion Phys., 1980, 33, 263. [all data]

Minnhagen, 1973
Minnhagen, L., Spectrum and the energy levels of neutral argon, Ar I, J. Opt. Soc. Am., 1973, 63, 1185. [all data]

Spohr, Guyon, et al., 1971
Spohr, R.; Guyon, P.M.; Chupka, W.A.; Berkowitz, J., Threshold photoelectron detector for use in the vacuum ultraviolet, Rev. Sci. Instrum., 1971, 42, 1872. [all data]

Yoshino, 1970
Yoshino, K., Absorption spectrum of the argon atom in the vacuum-ultraviolet region, J. Opt. Soc. Am., 1970, 60, 1220. [all data]

Yoshino, 1969
Yoshino, K., Absorption spectrum of the argon atom in the vacuum-ultraviolet region, J. Opt. Soc. Am., 1969, 59, 1525. [all data]

Hotop and Niehaus, 1969
Hotop, H.; Niehaus, A., Reactions of excited atoms molecules with atoms and molecules. II. Energy analysis of penning electrons, Z. Phys., 1969, 228, 68. [all data]

Collin and Natalis, 1968
Collin, J.E.; Natalis, P., Vibrational and electronic ionic states of nitric oxide. An accurate method for measuring ionization potentials by photoelectron spectroscopy, Intern. J. Mass Spectrom. Ion Phys., 1968, 1, 483. [all data]

Gallegos and Klaver, 1967
Gallegos, E.J.; Klaver, R.F., Automatic voltage scanner for a peak switching mass spectrometer, J.Sci. Instr., 1967, 44, 427. [all data]

Winters, Collins, et al., 1966
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, Henry's Law 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)
  Tboil	Boiling point
  Tc	Critical temperature
  Tfus	Fusion (melting) point
  Ttriple	Triple point temperature
  d(ln(kH))/d(1/T)	Temperature dependence parameter for Henry's Law constant
  k°H	Henry's Law constant at 298.15K
  ρc	Critical density

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