Uranium-238m

Properties and data of the isotope ^238mU.

Contents

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

General data

Name of the isotope:Uranium-238m; U-238mSymbol:^238mU or 238m92UMass 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-238m)
Excitation energy: 2557.9(5) keVNuclide 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)Half-life:280(6) nsDecay constant λ:2475525.6448569 s^-1Specific activity α:6.263850477190 × 10⁺²⁷ Bq g^-1
1.692932561402 × 10⁺¹⁷ Ci g^-1Spin and parity:
(nuclear angular momentum)0+

Radioactive Decay

Half-life T_½ = 280(6) ns respectively 2.8 × 10^-7 seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
Iso	²³⁸U	97.4(4) %
SZ	div	2.6(4) %

Nuclear Isomers

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

Nuclear Isomer	Excitation Energy	Half-life	Spin
²³⁸U		4.468(6) × 10⁹ a	0+

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-238m. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

Z	Isotone N = 146	Isobar A = 238
87	²³³Fr
88	²³⁴Ra
89	²³⁵Ac
90	²³⁶Th	²³⁸Th
91	²³⁷Pa	²³⁸Pa
92	²³⁸U	²³⁸U
93	²³⁹Np	²³⁸Np
94	²⁴⁰Pu	²³⁸Pu
95	²⁴¹Am	²³⁸Am
96	²⁴²Cm	²³⁸Cm
97	²⁴³Bk	²³⁸Bk
98	²⁴⁴Cf	²³⁸Cf
99	²⁴⁵Es
100	²⁴⁶Fm
101	²⁴⁷Md