Helium-4

Properties and data of the isotope ⁴He.

Contents

General Data

Parent Nuclides

Isotones und Isobares

Literature

General data

Name of the isotope:Helium-4; He-4Symbol:⁴He or 42HeMass number A:4 (= number of nucleons)Atomic number Z:2 (= number of protons)Neutrons N:2Isotopic mass:4.0026032541(4) u (atomic weight of Helium-4)Nuclide mass:4.0015061 u (calculated nuclear mass without electrons)Mass excess:2.42492 MeVMass defect:0.0303766419 u (per nucleus)Nuclear binding energy:28.29565967 MeV (per nucleus)
7.07391492 MeV (average binding energy per nucleon)Separation energy:S_N = 20.57762(0) MeV (first neutron)
S_P = 19.81386(0) MeV (first proton)Half-life:stableSpin and parity:
(nuclear angular momentum)0+Isobaric spin: 0Charge radius:1.67824(83) femtometer fmYear of discovery:1908

Parent Nuclides

Direct parent isotopes are: ⁵He, ⁵Li, ⁶Be.

Occurrence

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

	Atomic Mass m_a	Quantity	Half-life	Spin
Helium Isotopic mixture	4.002602 u	100 %
Isotope ⁴He	4.0026032541(4) u	99.9998(2) %	stable	0+
Isotope ³He	3.01602932(2) u	0.0002(2) %	stable	1/2+

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 2) and isobaric (same nucleon number A = 4) with Helium-4. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

Z	Isotone N = 2	Isobar A = 4
1	³H	⁴H
2	⁴He	⁴He
3	⁵Li	⁴Li
4	⁶Be
5	⁷B
6	⁸C
7	⁹N

External data and identifiers

Adopted Levels, Gammas:NuDat 4He

Literature and References

[1] - Julian J. Krauth, Karsten Schuhmann, Marwan Abdou Ahmed et al.:
Measuring the α-particle charge radius with muonic helium-4 ions.
In: Nature, 589, 527 - 531, (2021), DOI 10.1038/s41586-021-03183-1.