
	H	He
	Li	Be

Hydrogen - ₁H: thermochemistry and thermodynamics

Temperatures

Melting point: 14.01 [‑259.14 °C (‑434.45 °F)] K
Boiling point: 20.28 [‑252.87 °C (‑423.17 °F)] K
Liquid range: 6.27 K
Critical temperature: 33 [‑240 °C (‑400 °F)] K
Superconduction temperature: (no data) K

Image showing periodicity of melting point for the chemical elements as colour-coded squares on a periodic table grid.

Enthalpies

Enthalpy of fusion: 0.558 (per mol H atoms) kJ mol^-1
Enthalpy of vaporisation: 0.452 (per mole H atoms) kJ mol^-1
Enthalpy of atomisation: 218 kJ mol^-1

Thermodynamic data

This table gives a few thermodynamic data for hydrogen. Most values are those given in the NBS technical notes (reference 1) after conversion from the units used within those notes. Values labelled with an asterisk (*) are Committee on Data for Science and Technology (CODATA) agreed values for the thermodynamic properties of key chemical substances (reference 2). These values are published in a number of places including the WWW (reference 3).


State	Δ_fH°	Δ_fG°	S°	C_pH	H°_298.15‑H°₀
Units	kJ mol^‑1	kJ mol^‑1	J K^‑1 mol^‑1	J K^‑1 mol^‑1	kJ mol^‑1
Gas (H₂)	*0	0	*130.680 ± 0.003	28.82	*8.468 ± 0.001
Gas (atoms)	*217.998 ± 0.006	203.26	*114.717 ± 0.002	20.786	*6.197 ± 0.001
Gas (²H atoms)	221.67	206.52	123.24	20.786	6.20
Gas (²H₂; D₂)	0	0	144.85	29.20	8.569
Gas (H²H; HD)	0.33	-1.46	143.69	29.20	8.505

Notes

This tables gives a few thermodynamic data. Most values are those given in the NBS technical notes (reference 1) after conversion from the units used within those notes. Values labelled with an asterisk (*) are Committee on Data for Science and Technology (CODATA) agreed values for the thermodynamic properties of key chemical substances (reference 2). These values are published in a number of places including the WWW (reference 3).

References