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Properties and data of the isotope 1H.



Hydrogen-1 isotope

Hydrogen-1 is the isotope of the chemical element hydrogen with mass number 1, also known under the names protium and light hydrogen. The atomic nucleus of the nuclide consists of a proton. With a proportion of 99.98%, H-1 is not only the most common isotope of natural terrestrial hydrogen, but it is also the lightest and most abundant nuclide in the universe (approx. 90% of all atoms).

See also: list of Hydrogen isotopes.


General data

Name of the isotope:Hydrogen-1; H-1Other names:ProtiumSymbol:1H or 11HMass number A:1 (= number of nucleons)Atomic number Z:1 (= number of protons)Neutrons N:0Isotopic mass:1.0078250322(6) u (atomic weight of Hydrogen-1)Nuclide mass:1.0072765 u (calculated nuclear mass without electrons)Mass excess:7.28897 MeVMass defect:-2.0000001654807E-10 u (per nucleus)Nuclear binding energy:-1.9E-7 MeV (per nucleus)
-1.9E-7 MeV (average binding energy per nucleon)
Half-life:stableSpin and parity:
(nuclear angular momentum)
1/2+Magnetic dipole moment:μ(μN) = +2.792847351(28)Charge radius:0.8783(86) femtometer fmYear of discovery:1920


Parent Nuclides

Direct parent isotope is: 9B.



Comparison of the natural Hydrogen isotopes including isotopic abundance (mole fraction of the isotope mixture in percent):


Atomic Mass maQuantityHalf-lifeSpin
Isotopic mixture
1.008 u100 %
Isotope 3H3.01604928132(8) u
12.32(2) a1/2+
Isotope 1H1.0078250322(6) u99.99 %
[99.972 - 99.999 %]
Isotope 2H2.0141017781(8) u0.01 %
[0.001 - 0.028 %]


NMR data

Nuclear magnetic properties of the NMR active Nuclide 1H

Isotope:1H-NMRQuantity:99.99 % [99.972 - 99.999 %]Spin:1/2+Nuclearmagnetic moment
+2.792847351(28)Gyromagnetic ratio γ:26.675222 · 107 rad T-1 s-1Nuclear g-factor:gl = 5.585694702Resonance frequency:v0 = 42.5759 at 1 TFrequency ratio:Ξ(1H) = 100.0000 %Relative Sensitivity:1.00000 (H0 = const.)
1.00000 (v0 = const.)
[related to 1H = 1.000]
Reference compound:
1% solution of tetramethylsilane (TMS, Me4Si) in Chloroform-d (CDCl3).


Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 0) and isobaric (same nucleon number A = 1) with Hydrogen-1. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.


OZIsotone N = 0Isobar A = 1


External data and identifiers

InChI Key:YZCKVEUIGOORGS-IGMARMGPSA-NSMILES:[1H]PubChem:ID 5460654Adopted Levels, Gammas:NuDat 1H


Literature and References

[1] - Juven Wang, Zheyan Wan, Yi-Zhuang You:
Proton stability: From the standard model to beyond grand unification.
In: Physical Review D, 106, 025016, (2022), DOI 10.1103/PhysRevD.106.025016.

[2] - Seth Koren:
A Note on Proton Stability in the Standard Model.
In: Universe, 8(6), 308, (2022), DOI 10.3390/universe8060308.


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Last update: 2023-11-30

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