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Uranium-238

Properties and data of the isotope 238U.


Content

Uranium-238 (Uranium I) is the radioisotope of the element Uranium, whose atomic nucleus has 146 neutrons in addition to the element-specific 92 protons, resulting in a mass number of 238.

See also: list of Uranium isotopes.

 

General data

Name of the isotope:Uranium-238; U-238Other names:Uran ISymbol:238U or 23892UMass number A:238 (= number of nucleons)Atomic number Z:92 (= number of protons)Neutrons N:146Isotopic mass:238.05079(2) u (atomic weight of Uranium-238)Nuclide mass:238.0003273 u (calculated nuclear mass without electrons)Mass excess:47.31058 MeVMass defect:1.93419068 u (per nucleus)Nuclear binding energy:1801.68701328 MeV (per nucleus)
7.5701135 MeV (average binding energy per nucleon)
Separation energy:SN = 6.1537(13) MeV (first neutron)
SP = 7.509(13) MeV (first proton)
Half-life:4.468(6) × 109 aDecay constant λ:4.919326971729 × 10-18 s-1Specific activity α:12447.428554556 Bq g-1
3.364169879609 × 10-7 Ci g-1
Spin and parity:
(nuclear angular momentum)
0+Charge radius:5.8571(33) femtometer fmYear of discovery:1896

 

Radioactive Decay

Half-life T½ = 4.468(6) × 109 a respectively 1.40902848 × 1017 seconds s.

Decay modeDaughterProbabilityDecay energyγ energy
(intensity)
α234Thca. 100 %4.2699(21) MeV
SZdiv10-5 %

 

Graphic representation of the uranium-radium series, the natural radioactive decay series of the uranium isotope U-238.

 

Uranium radium series

 

Parent Nuclides

Direct parent isotopes are: 242Pu, 238Pa.

 

Occurrence

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

 

Atomic Mass maQuantityHalf-lifeSpin
Uranium
Isotopic mixture
238.02891 u100 %
Isotope 234U234.04095(2) u0.0054(5) %2.455(6) × 105 a0+
Isotope 235U235.04393(2) u0.7204(6) %7.04(1) × 108 a7/2-
Isotope 238U238.05079(2) u99.2742(10) %4.468(6) × 109 a0+

 

Nuclear Isomers

Nuclear isomers or excited states with the activation energy in keV related to the ground state.

Nuclear IsomerExcitation EnergyHalf-lifeSpin
238mU2557.9(5) keV280(6) ns0+

 

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 146) and isobaric (same nucleon number A = 238) with Uranium-238. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

 

OZIsotone N = 146Isobar A = 238
87233Fr
88234Ra
89235Ac
90236Th238Th
91237Pa238Pa
92238U238U
93239Np238Np
94240Pu238Pu
95241Am238Am
96242Cm238Cm
97243Bk238Bk
98244Cf238Cf
99245Es
100246Fm
101247Md

 

External data and identifiers

Adopted Levels, Gammas:NuDat 238U

 


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Last update: 2023-04-19


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