Uranium-239

Properties and data of the isotope ²³⁹U.

Contents

General Data

Radioactive Decay

Parent Nuclides

Formation

Isotones und Isobares

Uranium-239 is a radioisotope of the chemical element uranium, which has 147 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 239.

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

General data

Name of the isotope:Uranium-239; U-239Symbol:²³⁹U or 23992UMass number A:239 (= number of nucleons)Atomic number Z:92 (= number of protons)Neutrons N:147Nucleon pairing (Z - N):even - oddNuclear ratio (N/Z ratio):1.5978260869565 (= neutron-proton ratio)Neutron excess (N-Z):55Isotopic mass:239.0542920(16) u (atomic weight of Uranium-239)Nuclide mass:239.0038293 u (calculated nuclear mass without electrons)Mass excess:50.57267 MeVMass defect:1.939353596 u (per nucleus)Nuclear binding energy:1806.49623855 MeV (per nucleus)
7.55856167 MeV (average binding energy per nucleon)Separation energy:S_N = 4.80638(17) MeV (first neutron)
S_P = 7.610(16) MeV (first proton)Half-life:23.45(2) minDecay constant λ:0.00049264191937452 s^-1Specific activity α:1.241321770704 × 10⁺¹⁸ Bq g^-1
33549237.046059 Ci g^-1Spin and parity:
(nuclear angular momentum)5/2+Year of discovery:1937

Radioactive Decay

Half-life T_½ = 23.45(2) min (minutes) respectively 1.4070 × 10³ seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
β^-	²³⁹Np	100 %	1.2617(15) MeV	0.074664(1) MeV 53.2(17) %

The figure shows the natural decay scheme (²³⁹U decay series) for the nuclide uranium-239, whose end point is the stable lead nuclide Lead-207.

Parent Nuclides

Direct parent isotope is: ²³⁹Pa.

Formation

Uranium-239 is formed by neutron capture from Uranium-239, for example in nuclear reactors:

²³⁸U + ¹n → ²³⁹U.

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
^239m1U	133.7991(10) keV	0.78(4) μs	1/2+
^239m2U	+x keV	0.25 μs	(5/2+)

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 147) and isobaric (same nucleon number A = 239) with Uranium-239. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

Z	Isotone N = 147	Isobar A = 239
89	²³⁶Ac
90	²³⁷Th
91	²³⁸Pa	²³⁹Pa
92	²³⁹U	²³⁹U
93	²⁴⁰Np	²³⁹Np
94	²⁴¹Pu	²³⁹Pu
95	²⁴²Am	²³⁹Am
96	²⁴³Cm	²³⁹Cm
97	²⁴⁴Bk	²³⁹Bk
98	²⁴⁵Cf	²³⁹Cf
99	²⁴⁶Es
100	²⁴⁷Fm
101	²⁴⁸Md
102	²⁴⁹No