Neptunium-234

Properties and data of the isotope ²³⁴Np.

Contents

Neptunium-234 is a radioisotope of the chemical element neptunium, which has 141 neutrons in its atomic nucleus in addition to the element-specific 93 protons; the sum of the number of these atomic nucleus building blocks results in a mass number of 234. The very short-lived, only artificially produced, unstable and thus radioactive nuclide has no practical significance; the study of ²³⁴Np is exclusively for academic purposes.

In 1949 a research report presented the first identification of the isotope neptunium-234. In the experiment, uranium-233 was bombarded with 44-MeV alpha particles (helium-4 nuclei) from a 60-inch cyclotron, producing the nuclide through the fusion-evaporation reaction

²³³U(α,3n)²³⁴Np.

Following chemical separation, alpha-absorption and decay spectra together with complementary gamma-ray measurements provided clear evidence for the new isotope, which decays by orbital electron capture with a half-life of 4.40 days [E. K. Hyde et al., The Transuranium Elements: Research Papers, Paper 22.15 (1949)].

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

General data

Name of the isotope:Neptunium-234; Np-234Symbol:²³⁴Np or 23493NpMass number A:234 (= number of nucleons)Atomic number Z:93 (= number of protons)Neutrons N:141Nucleon pairing (Z - N):odd - oddNuclear ratio (N/Z ratio):1.5161290322581 (= neutron-proton ratio)Neutron excess (N-Z):48Isotopic mass:234.042893(9) u (atomic weight of Neptunium-234)Nuclide mass:233.9918819 u (calculated nuclear mass without electrons)Mass excess:39.95457 MeVMass defect:1.906588132 u (per nucleus)Nuclear binding energy:1775.97540543 MeV (per nucleus)
7.58963848 MeV (average binding energy per nucleon)Separation energy:S_N = 6.065(52) MeV (first neutron)
S_P = 4.253(9) MeV (first proton)Half-life:4.4(1) dDecay constant λ:1.823303820917 × 10^-6 s^-1Specific activity α:4.692389931634 × 10⁺¹⁵ Bq g^-1
126821.34950364 Ci g^-1Spin and parity:
(nuclear angular momentum)(0+)Year of discovery:1949

Radioactive Decay

Half-life T_½ = 4.4(1) d respectively 3.80160 × 10⁵ seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
EC/β⁺	²³⁴U	100 %	1.810(8) MeV

Parent Nuclides

Direct parent isotopes are: ²³⁸Am, ²³⁴Pu.

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 141) and isobaric (same nucleon number A = 234) with Neptunium-234. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

Z	Isotone N = 141	Isobar A = 234
83	²²⁴Bi
84	²²⁵Po
85	²²⁶At
86	²²⁷Rn
87	²²⁸Fr
88	²²⁹Ra	²³⁴Ra
89	²³⁰Ac	²³⁴Ac
90	²³¹Th	²³⁴Th
91	²³²Pa	²³⁴Pa
92	²³³U	²³⁴U
93	²³⁴Np	²³⁴Np
94	²³⁵Pu	²³⁴Pu
95	²³⁶Am	²³⁴Am
96	²³⁷Cm	²³⁴Cm
97	²³⁸Bk	²³⁴Bk
98	²³⁹Cf
99	²⁴⁰Es
100	²⁴¹Fm