Iodine

• Formula: I₂
• Molecular weight: 253.80894
• IUPAC Standard InChI: InChI=1S/I2/c1-2 Copy

  
• IUPAC Standard InChIKey: PNDPGZBMCMUPRI-UHFFFAOYSA-N Copy
• CAS Registry Number: 7553-56-2
• Chemical structure:
  This structure is also available as a 2d Mol file or as a computed 3d SD file
  The 3d structure may be viewed using Java or Javascript.
• Other names: I2; Eranol; Iode; Iodine-127; Iodio; Iosan Superdip; Jod; Jood; Molecular iodine; Tincture iodine; Vistarin; Iodine crystals; Iodine sublimed; Diiodine; Diatomic iodine
• Permanent link for this species. Use this link for bookmarking this species for future reference.
• Information on this page:
  • Gas phase thermochemistry data
  • Condensed phase thermochemistry data
  • Gas phase ion energetics data
  • Ion clustering data
  • References
  • Notes
• Other data available:
  • Phase change data
  • Reaction thermochemistry data: reactions 1 to 50, reactions 51 to 75
  • Henry's Law data
  • Constants of diatomic molecules
• Data at other public NIST sites:
  • 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
• Options:
  • Switch to calorie-based units

Data at NIST subscription sites:

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

NIST subscription sites provide data under the NIST Standard Reference Data Program, but require an annual fee to access. The purpose of the fee is to recover costs associated with the development of data collections included in such sites. Your institution may already be a subscriber. Follow the links above to find out more about the data in these sites and their terms of usage.

Gas phase thermochemistry data

Go To: Top, Condensed phase thermochemistry data, Gas phase ion energetics data, Ion clustering 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.

View plot Requires a JavaScript / HTML 5 canvas capable browser.

View table.

Condensed phase thermochemistry data

Go To: Top, Gas phase thermochemistry data, Gas phase ion energetics data, Ion clustering data, References, Notes

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

Liquid 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.

View plot Requires a JavaScript / HTML 5 canvas capable browser.

View table.

Solid 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.

View plot Requires a JavaScript / HTML 5 canvas capable browser.

View table.

Gas phase ion energetics data

Go To: Top, Gas phase thermochemistry data, Condensed phase thermochemistry data, Ion clustering 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:
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
B - John E. Bartmess

View reactions leading to I₂⁺ (ion structure unspecified)

Electron affinity determinations

Ionization energy determinations

Appearance energy determinations

Ion clustering data

Go To: Top, Gas phase thermochemistry data, Condensed phase 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 as indicated in comments:
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. Searches may be limited to ion clustering reactions. A general reaction search form is also available.

Clustering reactions

 +  = ( • )

By formula: I^- + I₂ = (I^- • I₂)

 +  = I₃^-

By formula: I^- + I₂ = I₃^-

I₃^- +  = (I₃^- • )

By formula: I₃^- + I₂ = (I₃^- • I₂)

References

Go To: Top, Gas phase thermochemistry data, Condensed phase thermochemistry data, Gas phase ion energetics data, Ion clustering 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]

Zanni, Taylor, et al., 1997
Zanni, M.T.; Taylor, T.R.; Greenblatt, J.; Soep, B.; Neumark, D.M., Characterization of the I2- Anion Ground State Using Conventional and Femtosecond Photoelectron Spectroscopy, J. Chem. Phys., 1997, 107, 19, 7613, https://doi.org/10.1063/1.475110 . [all data]

Auerbach, Baeda, et al., 1973
Auerbach, J.; Baeda, A.P.M.; Los, D.J., Fragmentation of Negative Ions Formed in Collisions of Alkali Atoms and Halogen Molecules, Physica, 1973, 64, 1, 134, https://doi.org/10.1016/0031-8914(73)90119-5 . [all data]

Hughes, Lifschitz, et al., 1973
Hughes, B.M.; Lifschitz, C.; Tiernan, T.O., Electron affinities from endothermic negative-ion charge-transfer reactions. III. NO, NO₂, S₂, CS₂, Cl₂, Br₂, I₂, and C₂H, J. Chem. Phys., 1973, 59, 3162. [all data]

Chupka, Berkowitz, et al., 1971
Chupka, W.A.; Berkowitz, J.; Gutman, D., Electron Affinities of Halogen Diatomic Molecules as Determined by Endoergic Charge Exchange, J. Chem. Phys., 1971, 55, 6, 2724, https://doi.org/10.1063/1.1676487 . [all data]

DeCorpo and Franklin, 1971
DeCorpo, J.J.; Franklin, J.L., Electron affinities of the halogen molecules by dissociative electron attachment, J. Chem. Phys., 1971, 54, 1885. [all data]

Moutinho, Aten, et al., 1971
Moutinho, A.M.C.; Aten, J.A.; Los, J., Temperature dependence of the total cross section for chemi-ionization in ackali halide-galogen collisions, Physica, 1971, 53, 471. [all data]

Ayala, Wentworth, et al., 1981
Ayala, J.A.; Wentworth, W.E.; Chen, E.C.M., Electron attachment to halogens, J. Phys. Chem., 1981, 85, 768. [all data]

Hubers, Kleyn, et al., 1976
Hubers, M.M.; Kleyn, A.W.; Los, J., Ion pair formation in alkali-halogen collisions at high velocities, Chem. Phys., 1976, 17, 303. [all data]

Cockett, Donovan, et al., 1996
Cockett, M.C.R.; Donovan, R.J.; Lawley, K.P., Zero kinetic energy pulsed field ionization (ZEKE-PFI) spectroscopy of electronically and vibrationally excited states of I₂+: The A ²Π_3/2,u state and a new electronic state, the a ⁴σ^-_u state, J. Chem. Phys., 1996, 105, 3347. [all data]

Cockett, Goode, et al., 1995
Cockett, M.C.R.; Goode, J.G.; Lawley, K.P.; Donovan, R.J., Zero kinetic energy photoelectron spectroscopy of Rydberg excited molecular iodine, J. Chem. Phys., 1995, 102, 5226. [all data]

Carlson, Gerard, et al., 1988
Carlson, T.A.; Gerard, P.; Pullen, B.P.; Grimm, F.A., Autoionization from the ione-pair orbitals of molecules containing iodine, J. Chem. Phys., 1988, 89, 1464. [all data]

Grade and Rosinger, 1985
Grade, M.; Rosinger, W., Correlation of electronic structures and stabilities of gaseous FeI₂, Fe₂I₂ and Fe₂I₄ molecules, solid [FeI₂], and iodine adsorbed on [Fe], Surf. Sci., 1985, 156, 920. [all data]

Grade and Rosinger, 1984
Grade, M.; Rosinger, W., A mass spectrometric investigation of iron(II)-iodide, Ber. Bunsen-Ges. Phys. Chem., 1984, 88, 767. [all data]

Grade, Rosinger, et al., 1984
Grade, M.; Rosinger, W.; Dowben, P.A., Core and valence electron binding energies of FeI₂ and stabilities of gas phase species, Ber. Bunsen-Ges. Phys. Chem., 1984, 88, 65. [all data]

Hoareau, Cabaud, et al., 1981
Hoareau, A.; Cabaud, B.; Melinon, P., Time-of-flight mass spectroscopy of supersonic beam of metallic vapours: Intensities and appearance potentials of Mx aggregates, Surf. Sci., 1981, 106, 195. [all data]

Pittermann and Weil, 1980
Pittermann, U.; Weil, K.G., Massenspektrometrische Untersuchungen an Silberhalogeniden V: Verdampfung von Silberiodid, Ber. Bunsen-Ges. Phys. Chem., 1980, 84, 542. [all data]

Higginson, Lloyd, et al., 1973
Higginson, B.R.; Lloyd, D.R.; Roberts, P.J., Variable temperature photoelectron spectroscopy. The adiabatic ionization potential of the iodine molecule, Chem. Phys. Lett., 1973, 19, 480. [all data]

Potts and Price, 1971
Potts, A.W.; Price, W.C., Photoelectron spectra of the halogens and mixed halides ICI and lBr, J. Chem. Soc. Faraday Trans., 1971, 67, 1242. [all data]

Dibeler, Walker, et al., 1971
Dibeler, V.H.; Walker, J.A.; McCulloh, K.E.; Rosenstock, H.M., Effect of hot bands on the ionization threshold of some diatomic halogen molecules, Intern. J. Mass Spectrom. Ion Phys., 1971, 7, 209. [all data]

Venkateswarlu, 1970
Venkateswarlu, P., Vacuum ultraviolet spectrum of the iodine molecule, Can. J. Phys., 1970, 48, 1055. [all data]

Myer and Samson, 1970
Myer, J.A.; Samson, J.A.R., Absorption cross section and photoionization yield of I₂ between 1050 and 2200 A, J. Chem. Phys., 1970, 52, 716. [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]

Cornford, Frost, et al., 1971
Cornford, A.B.; Frost, D.C.; McDowell, C.A.; Ragle, J.L.; Stenhouse, I.A., Photoelectron spectra of the halogens, J. Chem. Phys., 1971, 54, 2651. [all data]

Morrison, Hurzeler, et al., 1960
Morrison, J.D.; Hurzeler, H.; Inghram, M.G.; Stanton, H.E., Threshold law for the probability of excitation of molecules by photon impact. A study of the photoionization efficiencies of Br₂, I₂, HI, and CH₃I, J. Chem. Phys., 1960, 33, 821. [all data]

Watanabe, 1957
Watanabe, K., Ionization potentials of some molecules, J. Chem. Phys., 1957, 26, 542. [all data]

Downs and Adams, 1973
Downs, A.J.; Adams, G.J., Comprehensive Inorganic Chemistry, J. C. Bailar, H. J. Emeleus, R. Nyholm and A. F. Trotman - Dickerson, ed(s)., Pergamon Press, New York, 1973, 1543. [all data]

Taylor, Asmis, et al., 1999
Taylor, T.R.; Asmis, K.R.; Zanni, M.T.; Neumark, D.M., Characterization of the I-3 radical by anion photoelectron spectroscopy, J. Chem. Phys., 1999, 110, 16, 7607-7609, https://doi.org/10.1063/1.478672 . [all data]

Do, Klein, et al., 1997
Do, K.; Klein, T.P.; Pommerening, C.A.; Sunderlin, L.S., A New Flowing Afterglow-Guided Ion Beam Tandem Mass Spectrometer. Applications to the Thermochemistry of Polyiodide Ions, J. Am. Soc. Mass Spectrom., 1997, 8, 7, 688, https://doi.org/10.1016/S1044-0305(97)00116-5 . [all data]

Finch, Gates, et al., 1977
Finch, A.; Gates, P.N.; Peake, S.J., Thermochemistry of polyhalides. III. Cesium and rubidium tetrachloroiodates, J. Inorg. Nucl. Chem., 1977, 39, 2135. [all data]

Check, Faust, et al., 2001
Check, C.E.; Faust, T.O.; Bailey, J.M.; Wright, B.J.; Gilbert, T.M.; Sunderlin, L.S., Addition of Polarization and Diffuse Functions to the LANL2DZ Basis Set for P-Block Elements, J. Phys. Chem. A,, 2001, 105, 34, 8111, https://doi.org/10.1021/jp011945l . [all data]

Notes

Go To: Top, Gas phase thermochemistry data, Condensed phase thermochemistry data, Gas phase ion energetics data, Ion clustering data, References

• Symbols used in this document:
  

  AE	Appearance energy
  EA	Electron affinity
  IE (evaluated)	Recommended ionization energy
  S°gas,1 bar	Entropy of gas at standard conditions (1 bar)
  S°liquid,1 bar	Entropy of liquid at standard conditions (1 bar)
  S°solid	Entropy of solid at standard conditions
  S°solid,1 bar	Entropy of solid at standard conditions (1 bar)
  ΔfH°gas	Enthalpy of formation of gas at standard conditions
  ΔfH°liquid	Enthalpy of formation of liquid at standard conditions
  ΔrG°	Free energy of reaction at standard conditions
  ΔrH°	Enthalpy of reaction at standard conditions

• Data from NIST Standard Reference Database 69: NIST Chemistry WebBook
• The National Institute of Standards and Technology (NIST) uses its best efforts to deliver a high quality copy of the Database and to verify that the data contained therein have been selected on the basis of sound scientific judgment. However, NIST makes no warranties to that effect, and NIST shall not be liable for any damage that may result from errors or omissions in the Database.
• Customer support for NIST Standard Reference Data products.