Helium-7

Properties and data of the isotope ⁷He.

Contents

General Data

Radioactive Decay

Isotones und Isobares

See also: List of individual Helium isotopes (and general data sources).

General data

Name of the isotope:Helium-7; He-7Symbol:⁷He or 72HeMass number A:7 (= number of nucleons)Atomic number Z:2 (= number of protons)Neutrons N:5Nucleon pairing (Z - N):even - oddNuclear ratio (N/Z ratio):2.5 (= neutron-proton ratio)Neutron excess (N-Z):3Isotopic mass:7.027991(8) u (atomic weight of Helium-7)Nuclide mass:7.0268938 u (calculated nuclear mass without electrons)Mass excess:26.07345 MeVMass defect:0.030983644 u (per nucleus)Nuclear binding energy:28.86107848 MeV (per nucleus)
4.12301121 MeV (average binding energy per nucleon)Separation energy:
S_P = 23.092(254) MeV (first proton)Half-life:2.85688 zsDecay constant λ:2.426238345887 × 10⁺²⁰ s^-1Specific activity α:2.08730701124 × 10⁺⁴³ Bq g^-1
5.641370300662 × 10⁺³² Ci g^-1Spin and parity:
(nuclear angular momentum)(3/2)-Isobaric spin: 3/2Mirror nucleus:Boron-7Year of discovery:1967

Radioactive Decay

Half-life T_½ = 2.85688 zs respectively 2.85688 × 10^-21 seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
n	⁶He		11.166(8) MeV

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 5) and isobaric (same nucleon number A = 7) with Helium-7. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.