Hydrogen atom

Formula: H
Molecular weight: 1.00794
IUPAC Standard InChI: InChI=1S/H
IUPAC Standard InChIKey: YZCKVEUIGOORGS-UHFFFAOYSA-N
CAS Registry Number: 12385-13-6
Chemical structure:
This structure is also available as a 2d Mol file
Isotopologues:
- Tritium
- Deuterium
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Gas phase thermochemistry data

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Quantity	Value	Units	Method	Reference	Comment
Δ_fH°_gas	52.103 ± 0.001	kcal/mol	Review	Cox, Wagman, et al., 1984	CODATA Review value
Δ_fH°_gas	52.103	kcal/mol	Review	Chase, 1998	Data last reviewed in March, 1982
Quantity	Value	Units	Method	Reference	Comment
S°_{gas,1 bar}	27.4180 ± 0.0005	cal/mol*K	Review	Cox, Wagman, et al., 1984	CODATA Review value
S°_{gas,1 bar}	27.419	cal/mol*K	Review	Chase, 1998	Data last reviewed in March, 1982

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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Temperature (K)	298. to 6000.
A	4.967981
B	1.159331×10^-10
C	-3.783261×10^-11
D	3.645079×10^-12
E	7.639451×10^-12
F	50.62189
G	33.43000
H	52.10311
Reference	Chase, 1998
Comment	Data last reviewed in March, 1982

Reaction thermochemistry data

Go To: Top, Gas phase thermochemistry data, References, Notes

Data compiled as indicated in comments:
MS - José A. Martinho Simões
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.

Individual Reactions

(solution) = Hydrogen atom (solution) + C₅MnO₅ (solution)

By formula: C₅HMnO₅ (solution) = H (solution) + C₅MnO₅ (solution)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	68.0 ± 1.0	kcal/mol	EChem	Parker, Handoo, et al., 1991	solvent: Acetonitrile; Please also see Tilset and Parker, 1989. The reaction enthalpy was obtained from the pKa of the hydride complex (MH), 14.1, and from the oxidation potential of the anion (M-), Mn(CO)5(-), by using the equation: ΔH_rxn [kJ/mol] = 5.71pKa(MH) + 96.485(Eo)ox(M-) + C. C is a constant that was calculated as 59.49 kcal/mol Parker, Handoo, et al., 1991, by adjusting the previous equation to the calorimetrically derived values for the reactions Cr(Cp)(CO)3(H)(solution) = Cr(Cp)(CO)3(solution) + H(solution), 61.5 ± 1.0 kcal/mol, and Cr(Cp)(CO)2(PPh3)(H)(solution) = Cr(Cp)(CO)2(PPh3)(solution) + H(solution), 59.8 ± 1.0 kcal/mol Kiss, Zhang, et al., 1990. C depends on the solvent and on the reference electrode. The value given implies that the electrode potentials are referenced to ferrocene/ferricinium electrode; MS
Δ_rH°	64.46	kcal/mol	KinS	Billmers, Griffith, et al., 1986	solvent: Benzene; Please also see Sweany, Butler S.C., et al., 1981. The reaction enthalpy was derived according to the following procedure: the activation energy for the reaction 9,10-Me2C14H8(solution) + 2Mn(CO)5(H)(solution) = 9,10-Me2C14H10(solution) + Mn2(CO)10(solution), 21.7 kcal/mol, was reported in Sweany, Butler S.C., et al., 1981. The rate-limiting step of this reaction is the abstraction of hydrogen from Mn(CO)5(H), producing Mn(CO)5 and 9,10-Me2C14H9 radicals. Therefore, the activation energy is approximately equal to the difference between the enthalpies of the reactions Mn(CO)5(H)(solution) = Mn(CO)5(solution) + H(solution) and 9,10-Me2C14H9(solution) = 9,10-Me2C14H8(solution). The latter was taken as 42.76 kcal/mol Billmers, Griffith, et al., 1986; MS

C₇H₆FeO₂ (solution) = C₇H₅FeO₂ (solution) + Hydrogen atom (solution)

By formula: C₇H₆FeO₂ (solution) = C₇H₅FeO₂ (solution) + H (solution)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	57.1 ± 1.0	kcal/mol	EChem	Parker, Handoo, et al., 1991	solvent: Acetonitrile; Please also see Tilset and Parker, 1989. The reaction enthalpy was obtained from the pKa of the hydride complex (MH), 19.4, and from the oxidation potential of the anion (M-), Fe(Cp)(CO)2(-), by using the equation: ΔH_rxn [kJ/mol] = 5.71pKa(MH) + 96.485(Eo)ox(M-) + C. C is a constant that was calculated as 59.49 kcal/mol Parker, Handoo, et al., 1991, by adjusting the previous equation to the calorimetrically derived values for the reactions Cr(Cp)(CO)3(H)(solution) = Cr(Cp)(CO)3(solution) + H(solution), 61.5 ± 1.0 kcal/mol, and Cr(Cp)(CO)2(PPh3)(H)(solution) = Cr(Cp)(CO)2(PPh3)(solution) + H(solution), 59.8 ± 1.0 kcal/mol Kiss, Zhang, et al., 1990. C depends on the solvent and on the reference electrode. The value given implies that the electrode potentials are referenced to ferrocene/ferricinium electrode; MS

C₅HO₅Re (solution) = Hydrogen atom (solution) + C₅O₅Re (solution)

By formula: C₅HO₅Re (solution) = H (solution) + C₅O₅Re (solution)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	74.7 ± 1.0	kcal/mol	EChem	Parker, Handoo, et al., 1991	solvent: Acetonitrile; Please also see Tilset and Parker, 1989. The reaction enthalpy was obtained from the pKa of the hydride complex (MH), 21.1, and from the oxidation potential of the anion (M-), Re(CO)5(-), by using the equation: ΔH_rxn [kJ/mol] = 5.71pKa(MH) + 96.485(Eo)ox(M-) + C. C is a constant that was calculated as 59.49 kcal/mol Parker, Handoo, et al., 1991, by adjusting the previous equation to the calorimetrically derived values for the reactions Cr(Cp)(CO)3(H)(solution) = Cr(Cp)(CO)3(solution) + H(solution), 61.5 ± 1.0 kcal/mol, and Cr(Cp)(CO)2(PPh3)(H)(solution) = Cr(Cp)(CO)2(PPh3)(solution) + H(solution), 59.8 ± 1.0 kcal/mol Kiss, Zhang, et al., 1990. C depends on the solvent and on the reference electrode. The value given implies that the electrode potentials are referenced to ferrocene/ferricinium electrode; MS

(solution) = Hydrogen atom (solution) + (solution)

By formula: C₄HCoO₄ (solution) = H (solution) + C₄CoO₄ (solution)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	66.4 ± 1.0	kcal/mol	EChem	Parker, Handoo, et al., 1991	solvent: Acetonitrile; Please also see Tilset and Parker, 1989. The reaction enthalpy was obtained from the pKa of the hydride complex (MH), 8.3, and from the oxidation potential of the anion (M-), Co(CO)4(-), by using the equation: ΔH_rxn [kJ/mol] = 5.71pKa(MH) + 96.485(Eo)ox(M-) + C. C is a constant that was calculated as 59.49 kcal/mol Parker, Handoo, et al., 1991, by adjusting the previous equation to the calorimetrically derived values for the reactions Cr(Cp)(CO)3(H)(solution) = Cr(Cp)(CO)3(solution) + H(solution), 61.5 ± 1.0 kcal/mol, and Cr(Cp)(CO)2(PPh3)(H)(solution) = Cr(Cp)(CO)2(PPh3)(solution) + H(solution), 59.8 ± 1.0 kcal/mol Kiss, Zhang, et al., 1990. C depends on the solvent and on the reference electrode. The value given implies that the electrode potentials are referenced to ferrocene/ferricinium electrode; MS

C₄H₂FeO₄ (g) = 2 Hydrogen atom (g) + C₄FeO₄ (g)

By formula: C₄H₂FeO₄ (g) = 2H (g) + C₄FeO₄ (g)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	130.	kcal/mol	EST	Miller and Beauchamp, 1991	Please also see Martinho Simões and Beauchamp, 1990. The reaction enthalpy was estimated from the activation enthalpy for thermal decomposition in solution, 26. ± 2. kcal/mol Pearson and Mauermann, 1982, yielding Fe(CO)4 and H2, and from the activation enthalpy of the oxidative addition of H2 to Fe(CO)4 in a rare gas matrix, ca. 0. kcal/mol Sweany, 1981, yielding Fe(CO)4H2. The enthalpy of formation relies on -105.1 ± 3.4 kcal/mol for the enthalpy of formation of Fe(CO)4(g); MS

(g) = Hydrogen atom (g) + C₅MnO₅ (g)

By formula: C₅HMnO₅ (g) = H (g) + C₅MnO₅ (g)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	58.6 ± 4.1	kcal/mol	PIMS	Martinho Simões and Beauchamp, 1990	The reaction enthalpy was derived from the appearance energy of Mn(CO)5(+), 237.5 ± 2.3 kcal/mol, using Mn(CO)5(H) as the neutral precursor, together with the adiabatic ionization energy of Mn(CO)5 radical, 179. ± 3.3 kcal/mol Martinho Simões and Beauchamp, 1990; MS

C₃H₁₀Ge (g) = C₃H₉Ge (g) + Hydrogen atom (g)

By formula: C₃H₁₀Ge (g) = C₃H₉Ge (g) + H (g)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	79.8 ± 2.9	kcal/mol	ICR	Brinkman, Salomon, et al., 1995	The reaction enthalpy was derived from the acidity of Ge(Me)3(H)(g), 361.5 ± 2.8 kcal/mol, the electron affinity of Ge(Me)3(g), 31.91 ± 0.69 kcal/mol Brinkman, Salomon, et al., 1995, and the ionization energy of H(g), 313.58 kcal/mol Lias, Bartmess, et al., 1988.; MS

C₃H₁₀Sn (g) = Hydrogen atom (g) + (g)

By formula: C₃H₁₀Sn (g) = H (g) + C₃H₉Sn (g)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	74.6 ± 2.5	kcal/mol	ICR	Brinkman, Salomon, et al., 1995	The reaction enthalpy was derived from the acidity of Sn(Me)3(H)(g), 349.0 ± 2.0 kcal/mol, the electron affinity of Sn(Me)3(g), 39.2 ± 1.5 kcal/mol Brinkman, Salomon, et al., 1995, and the ionization energy of H(g), 313.58 kcal/mol Lias, Bartmess, et al., 1988.; MS

(g) = Hydrogen atom (g) + (g)

By formula: H₄Ge (g) = H (g) + H₃Ge (g)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	83.4 ± 2.0	kcal/mol	PIMS	Berkowitz, Ellison, et al., 1994	Please also see Ruscic, Schwarz, et al., 1990. Value recommended in the critical survey Berkowitz, Ellison, et al., 1994.; MS
Δ_rH°	<85.6	kcal/mol	PIMS	Ruscic, Schwarz, et al., 1990	Temperature: 0 K. A value of 82. ± 2. kcal/mol is recommended in Ruscic, Schwarz, et al., 1990.; MS

e^- + = Hydrogen atom

By formula: e^- + H⁺ = H

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	315.10	kcal/mol	Acid	Wagman, Evans, et al., 1982	gas phase; Using the "electron convention". Acid = H.; B
Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	314.00	kcal/mol	H-TS	Wagman, Evans, et al., 1982	gas phase; Using the "electron convention". Acid = H.; B

(g) = Hydrogen atom (g) + (g)

By formula: H₃Ge (g) = H (g) + H₂Ge (g)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	>56.4	kcal/mol	PIMS	Ruscic, Schwarz, et al., 1990	Temperature: 0 K. A value of 59.0 kcal/mol is recommended in Ruscic, Schwarz, et al., 1990.; MS

(g) = HGe (g) + Hydrogen atom (g)

By formula: H₂Ge (g) = HGe (g) + H (g)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	<68.8	kcal/mol	PIMS	Ruscic, Schwarz, et al., 1990	Temperature: 0 K. A value of 66.2 kcal/mol is recommended in Ruscic, Schwarz, et al., 1990.; MS

HGe (g) = Hydrogen atom (g) + (g)

By formula: HGe (g) = H (g) + Ge (g)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	>53.8	kcal/mol	PIMS	Ruscic, Schwarz, et al., 1990	Temperature: 0 K. A value of 63.1 kcal/mol is recommended in Ruscic, Schwarz, et al., 1990.; MS

H₃Sb (g) = Hydrogen atom (g) + H₂Sb (g)

By formula: H₃Sb (g) = H (g) + H₂Sb (g)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	68.91 ± 0.50	kcal/mol	PIMS	Berkowitz, Ellison, et al., 1994	Value recommended in the critical survey Berkowitz, Ellison, et al., 1994.; MS

C₁₃H₂₆IrP (solution) = C₁₃H₂₄IrP (solution) + 2 Hydrogen atom (g)

By formula: C₁₃H₂₆IrP (solution) = C₁₃H₂₄IrP (solution) + 2H (g)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	148.	kcal/mol	EST	Nolan, Hoff, et al., 1987	Please also see Stoutland, Bergman, et al., 1988.; MS

(CAS Reg. No. 952499-85-3 • 4294967295 Hydrogen atom ) + = CAS Reg. No. 952499-85-3

By formula: (CAS Reg. No. 952499-85-3 • 4294967295H) + H = CAS Reg. No. 952499-85-3

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	44.7 ± 4.2	kcal/mol	N/A	Calvi, Andrews, et al., 2007	gas phase; B

C₁₃H₂₆IrP (solution) = C₁₃H₂₅IrP (solution) + Hydrogen atom (g)

By formula: C₁₃H₂₆IrP (solution) = C₁₃H₂₅IrP (solution) + H (g)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	72.9 ± 4.3	kcal/mol	PAC	Nolan, Hoff, et al., 1987	MS

References

Go To: Top, Gas phase thermochemistry data, Reaction thermochemistry data, Notes

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]

Parker, Handoo, et al., 1991
Parker, V.D.; Handoo, K.L.; Roness, F.; Tilset, M., J. Am. Chem. Soc., 1991, 113, 7493. [all data]

Tilset and Parker, 1989
Tilset, M.; Parker, V.D., J. Am. Chem. Soc., 1989, 111, 6711; ibid. 1990. [all data]

Kiss, Zhang, et al., 1990
Kiss, G.; Zhang, K.; Mukerjee, S.L.; Hoff, C.; Roper, G.C., J. Am. Chem. Soc., 1990, 112, 5657. [all data]

Billmers, Griffith, et al., 1986
Billmers, R.; Griffith, L.L.; Stein, S.E., J. Phys. Chem., 1986, 90, 517. [all data]

Sweany, Butler S.C., et al., 1981
Sweany, R.; Butler S.C.; Halpern, J., J. Organometal. Chem., 1981, 213, 487. [all data]

Miller and Beauchamp, 1991
Miller, A.E.S.; Beauchamp, J.L., J. Am. Chem. Soc., 1991, 113, 8765. [all data]

Martinho Simões and Beauchamp, 1990
Martinho Simões, J.A.; Beauchamp, J.L., Chem. Rev., 1990, 90, 629. [all data]

Pearson and Mauermann, 1982
Pearson, R.G.; Mauermann, H., J. Am. Chem. Soc., 1982, 104, 500. [all data]

Sweany, 1981
Sweany, R.L., J. Am. Chem. Soc., 1981, 103, 2410. [all data]

Brinkman, Salomon, et al., 1995
Brinkman, E.A.; Salomon, K.; Tumas, W.; Brauman, J.I., Electron affinities and gas-phase acidities of organogermanium and organotin compounds, J. Am. Chem. Soc., 1995, 117, 17, 4905, https://doi.org/10.1021/ja00122a022 . [all data]

Lias, Bartmess, et al., 1988
Lias, S.G.; Bartmess, J.E.; Liebman, J.F.; Holmes, J.L.; Levin, R.D.; Mallard, W.G., Gas-Phase Ion and Neutral Thermochemistry, J. Phys. Chem. Ref. Data, 1988, 17, Suppl. 1. [all data]

Berkowitz, Ellison, et al., 1994
Berkowitz, J.; Ellison, G.B.; Gutman, D., Three methods to measure RH bond energies, J. Phys. Chem., 1994, 98, 2744. [all data]

Ruscic, Schwarz, et al., 1990
Ruscic, B.; Schwarz, M.; Berkowitz, J., Photoionization studies of GeH_n(n = 2-4), J. Chem. Phys., 1990, 92, 1865. [all data]

Wagman, Evans, et al., 1982
Wagman, D.D.; Evans, W.H.; Parker, V.B.; Schumm, R.H.; Halow, I.; Bailey, S.M.; Churney, K.L.; Nuttall, R.L., The NBS Tables of Chemical Thermodynamic Properties (NBS Tech Note 270), J. Phys. Chem. Ref. Data, Supl. 1, 1982, 11. [all data]

Nolan, Hoff, et al., 1987
Nolan, S.P.; Hoff, C.D.; Stoutland, P.O.; Newman, L.J.; Buchanan, J.M.; Bergman, R.G.; Yang, G.K.; Peters, K.S., J. Am. Chem. Soc., 1987, 109, 3143. [all data]

Stoutland, Bergman, et al., 1988
Stoutland, P.O.; Bergman, R.G.; Nolan, S.P.; Hoff, C.D., Polyhedron, 1988, 7, 1429. [all data]

Calvi, Andrews, et al., 2007
Calvi, R.M.D.; Andrews, D.H.; Lineberger, W.C., Negative ion photoelectron spectroscopy of copper hydrides, Chem. Phys. Lett., 2007, 442, 1-3, 12-16, https://doi.org/10.1016/j.cplett.2007.05.060 . [all data]

Notes

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

Symbols used in this document:

S°_{gas,1 bar}	Entropy of gas at standard conditions (1 bar)
Δ_fH°_gas	Enthalpy of formation of gas at standard conditions
Δ_rG°	Free energy of reaction at standard conditions
Δ_rH°	Enthalpy of reaction at standard conditions

Data from NIST Standard Reference Database 69: NIST Chemistry WebBook
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