Neptunium-231

Properties and data of the isotope ²³¹Np.

Content

Neptunium-231 is the very short-lived radioisotope of the element Neptunium, whose atomic nucleus has 138 neutrons in addition to the element-specific 93 protons, resulting in a mass number of 231: ²³¹Np.

General data

Name of the isotope:Neptunium-231; Np-231Symbol:²³¹Np or 23193NpMass number A:231 (= number of nucleons)Atomic number Z:93 (= number of protons)Neutrons N:138Isotopic mass:231.03824(5) u (atomic weight of Neptunium-231)Nuclide mass:230.9872289 u (calculated nuclear mass without electrons)Mass excess:35.62033 MeVMass defect:1.885246384 u (per nucleus)Nuclear binding energy:1756.09569522 MeV (per nucleus)
7.60214587 MeV (average binding energy per nucleon)Separation energy:S_N = 7.68(7) MeV (first neutron)
S_P = 3.28(5) MeV (first proton)Half-life:48.8(2) minDecay constant λ:0.00023673059445353 s^-1Specific activity α:6.171536734440 × 10⁺¹⁷ Bq g^-1
16679829.012001 Ci g^-1Spin and parity:
(nuclear angular momentum)(5/2-)Year of discovery:1950

Radioactive Decay

Half-life T_½ = 48.8(2) min (minutes) respectively 2.928 × 10³ seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
α	²²⁷Pa	2(1) %	6.37(5) MeV
EE	²³¹U	98(1) %	1.82(5) MeV

Parent Nuclides

Direct parent isotopes are: ²³⁵Am, ²³¹Pu.

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 138) and isobaric (same nucleon number A = 231) with Neptunium-231. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

OZ	Isotone N = 138	Isobar A = 231
82	²²⁰Pb
83	²²¹Bi
84	²²²Po
85	²²³At
86	²²⁴Rn
87	²²⁵Fr	²³¹Fr
88	²²⁶Ra	²³¹Ra
89	²²⁷Ac	²³¹Ac
90	²²⁸Th	²³¹Th
91	²²⁹Pa	²³¹Pa
92	²³⁰U	²³¹U
93	²³¹Np	²³¹Np
94	²³²Pu	²³¹Pu
95	²³³Am	²³¹Am
96	²³⁴Cm
97	²³⁵Bk