Neptunium-239

Properties and data of the isotope ²³⁹Np.

Content

General data

Name of the isotope:Neptunium-239; Np-239Symbol:²³⁹Np or 23993NpMass number A:239 (= number of nucleons)Atomic number Z:93 (= number of protons)Neutrons N:146Isotopic mass:239.0529376(14) u (atomic weight of Neptunium-239)Nuclide mass:239.0019265 u (calculated nuclear mass without electrons)Mass excess:49.31106 MeVMass defect:1.939868112 u (per nucleus)Nuclear binding energy:1806.97550712 MeV (per nucleus)
7.56056698 MeV (average binding energy per nucleon)Separation energy:S_N = 6.2149(10) MeV (first neutron)
S_P = 5.2857(15) MeV (first proton)Half-life:2.356(3) dDecay constant λ:3.405151448232 × 10^-6 s^-1Specific activity α:8.580042540031 × 10⁺¹⁵ Bq g^-1
231893.04162247 Ci g^-1Spin and parity:
(nuclear angular momentum)5/2+Year of discovery:1940

Radioactive Decay

Half-life T_½ = 2.356(3) d respectively 2.035584 × 10⁵ seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
β^-	²³⁹Pu	100 %	0.7228(9) MeV

Parent Nuclides

Direct parent isotopes are: ²⁴³Am, ²³⁹U.

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 146) and isobaric (same nucleon number A = 239) with Neptunium-239. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

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