Uranium-229

Properties and data of the isotope ²²⁹U.

Contents

General Data

Radioactive Decay

Parent Nuclides

Isotones und Isobares

Literature

Uranium-229 is a radioisotope of the chemical element uranium, which has 137 neutrons in its atomic nucleus in addition to the element-specific 92 protons; the sum of the number of these atomic nucleus building blocks results in a mass number of 229. The very short-lived, only artificially produced, unstable and thus radioactive nuclide has no practical significance; the study of ²²⁹U is exclusively for academic purposes.

The first observation of the radionuclide was reported in 1949; according to this report, uranium-229 was formed by the irradiation of natural Th templates with alpha particles [1].

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

General data

Name of the isotope:Uranium-229; U-229Symbol:²²⁹U or 22992UMass number A:229 (= number of nucleons)Atomic number Z:92 (= number of protons)Neutrons N:137Nucleon pairing (Z - N):even - oddNuclear ratio (N/Z ratio):1.4891304347826 (= neutron-proton ratio)Neutron excess (N-Z):45Isotopic mass:229.033506(6) u (atomic weight of Uranium-229)Nuclide mass:228.9830433 u (calculated nuclear mass without electrons)Mass excess:31.21064 MeVMass defect:1.873490436 u (per nucleus)Nuclear binding energy:1745.14510019 MeV (per nucleus)
7.62072096 MeV (average binding energy per nucleon)Separation energy:S_N = 6.081(15) MeV (first neutron)
S_P = 5.002(7) MeV (first proton)Half-life:57.8(3) minDecay constant λ:0.0001998694292272 s^-1Specific activity α:5.256077975551 × 10⁺¹⁷ Bq g^-1
14205616.15014 Ci g^-1Spin and parity:
(nuclear angular momentum)3/2+Year of discovery:1949

Radioactive Decay

Half-life T_½ = 57.8(3) min (minutes) respectively 3.468 × 10³ seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
α	²²⁵Th	ca. 20 %	6.476(3) MeV
EC	²²⁹Pa	ca. 80 %	1.314(7) MeV

Parent Nuclides

Direct parent isotopes are: ²³³Pu, ²²⁹Np.

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 137) and isobaric (same nucleon number A = 229) with Uranium-229. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

Z	Isotone N = 137	Isobar A = 229
82	²¹⁹Pb
83	²²⁰Bi
84	²²¹Po
85	²²²At	²²⁹At
86	²²³Rn	²²⁹Rn
87	²²⁴Fr	²²⁹Fr
88	²²⁵Ra	²²⁹Ra
89	²²⁶Ac	²²⁹Ac
90	²²⁷Th	²²⁹Th
91	²²⁸Pa	²²⁹Pa
92	²²⁹U	²²⁹U
93	²³⁰Np	²²⁹Np
94	²³¹Pu	²²⁹Pu
95	²³²Am	²²⁹Am
96	²³³Cm
97	²³⁴Bk

External data and identifiers

Adopted Levels, Gammas:NuDat 229U

Literature and References

[1] - W. W. Meinke, A. Ghiorso, G. T. Seaborg:
Three Additional Collateral Alpha-Decay Chains.
In: Physical Review, 75, 314, (1949), DOI 10.1103/PhysRev.75.314.