Uranium-229

Properties and data of the isotope ²²⁹U.

Content

Uranium-229 is the short-lived radioisotope of the element uranium, whose atomic nucleus has 137 neutrons in addition to the element-specific 92 protons, resulting in a mass number of 229: ²²⁹U.

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:137Isotopic 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 = 6.083(15) MeV (first neutron)
S_P = 5.002(7) MeV (first proton)Half-life:58(3) minDecay constant λ:0.00019918022429883 s^-1Specific activity α:5.237953568739 × 10⁺¹⁷ Bq g^-1
14156631.266864 Ci g^-1Spin and parity:
(nuclear angular momentum)(3/2+)Year of discovery:1949

Radioactive Decay

Half-life T_½ = 58(3) min (minutes) respectively 3.480 × 10³ seconds s.

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

Parent Nuclides

Direct parent isotope is: ²³³Pu.

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.

OZ	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