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Properties and data of the isotope 3H.


See also: list of Hydrogen isotopes.


General data

Name of the isotope:Hydrogen-3; H-3Namen:TritiumSymbol:3HMass number A:3Atomic number Z:1 (= number of protons)Neutrons N:2Isotopic mass:3.01604928132(8) u (atomic weight of Hydrogen-3)Nuclide mass:3.0155007 u (calculated nuclear mass without electrons)Mass excess:14.94981 MeVMass defect:0.0091055826800002 u (per nucleus)Nuclear binding energy:8.48179563 MeV (per nucleus)
2.82726521 MeV (average binding energy per nucleon)
Half-life:12.32(2) aDecay constant λ:1.784052415191 × 10-9 s-1Spin and parity:1/2+Charge radius:1.7591(363) femtometer fmYear of discovery:1934


Radioactive Decay

Half-life T½ = 12.32(2) a respectively 3.88524 × 108 seconds s.

Decay modeDaughterProbabilityDecay energyγ energy
β-3He100 %0,018592(0) MeV


Parent Nuclides

Direct parent isotopes are: 4H, 5H.



Comparison of the natural Wasserstoff isotopes including isotopic abundance (proportion of the isotope mixture):


Atomic Mass maQuantityHalf-lifeSpin
Isotopic mixture
1,008 u100 %
Isotope 1H1,0078250322(6) u99,99 %stable1/2+
Isotope 2H2,0141017781(8) u0,01 %stable1+
Isotope 3H3,01604928132(8) u12.32(2) a1/2+


NMR data

3H belongs to the NMR active Nuclides.

Isotope:3H-NMRQuantity:SpurenSpin:1/2+Nuclearmagnetic moment
+ 2,978962460(14)Gyromagnetic ratio
107 rad T-1 s-1:
28,535Resonance frequency
v0 at 1 T:
45,4148Relative Sensitivity:1,21354 (H0 = const.)
1,0667 (v0 = const.)
[related to 1H = 1,000]


Radiation Protection

Als Zielorgan bzw. kritisches Organ des radioaktiven Tritiums gilt der ganze Körper. Die biologische Halbwertszeit beträgt 19 Tage.

The German Radiation Protection Ordinance, for example, specifies the following limit values for the isotope Hydrogen-3 (exemption limits, clearance values and other values as a radioactive or highly radioactive source of radiation (HASS)):

Isotope:H-3Exemption level:109 BqExemption level per gram:100 Bq/g
Unrestricted handling of solids and liquids.
Activity HASS:2000 TBqSurface contamination:100 Bq/cm2Half-life:12.3 a


Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 2) and isobaric (same nucleon number A = 3) with Hydrogen-3. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.


OZIsotone N = 2Isobar A = 3


External data and identifiers

CAS:10028-17-8Adopted Levels, Gammas:NuDat 3H


Category: Isotopes

Last update: 28.01.2022

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