Uranium-225

Properties and data of the isotope ²²⁵U.

Contents

General Data

Radioactive Decay

Parent Nuclides

Isotones und Isobares

Literature

Uranium-225 is a radioisotope of the chemical element uranium, which has 133 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 225. The very short-lived, only artificially produced, unstable and thus radioactive nuclide has no practical significance; the study of ²²⁵U is exclusively for academic purposes and experimental research.

In 1989 a Soviet research group reported for the first time on the isotope neptunium-225. In the experiments described, 100–130 MeV neon-22 ions from a cyclotron struck an enriched lead-208 target, so that the nuclide was formed in the fusion–evaporation reaction

²⁰⁸Pb(²²Ne,5n)²²⁵U

. After kinematic separation of the recoiling nuclei and their implantation in a silicon surface detector, characteristic α transitions could be identified, whose correlations were unambiguously assigned to the isotope neptunium-225 [1].

A little later in the same year, another group also reported an observation of ²²⁵U: A hafnium-180 target was bombarded with calcium-48 ions at a primary beam energy of 4.24 MeV per nucleon. In this experiment the nuclide was produced in the reaction:

¹⁸⁰Hf(⁴⁸Ca,3n)²²⁵U [2].

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

General data

Name of the isotope:Uranium-225; U-225Symbol:²²⁵U or 22592UMass number A:225 (= number of nucleons)Atomic number Z:92 (= number of protons)Neutrons N:133Nucleon pairing (Z - N):even - oddNuclear ratio (N/Z ratio):1.445652173913 (= neutron-proton ratio)Neutron excess (N-Z):41Isotopic mass:225.029385(11) u (atomic weight of Uranium-225)Nuclide mass:224.9789223 u (calculated nuclear mass without electrons)Mass excess:27.37195 MeVMass defect:1.842951772 u (per nucleus)Nuclear binding energy:1716.69851791 MeV (per nucleus)
7.62977119 MeV (average binding energy per nucleon)Separation energy:S_N = 6.442(18) MeV (first neutron)
S_P = 3.779(12) MeV (first proton)Half-life:62(4) msDecay constant λ:11.179793234838 s^-1Specific activity α:2.992279539784 × 10⁺²² Bq g^-1
808724199941.86 Ci g^-1Spin and parity:
(nuclear angular momentum)(5/2+)Year of discovery:1989

Radioactive Decay

Half-life T_½ = 62(4) ms respectively 6.2 × 10^-2 seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
α	²²¹Th	100 %	8.007(6) MeV

Parent Nuclides

Direct parent isotope is: ²²⁹Pu.

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 133) and isobaric (same nucleon number A = 225) with Uranium-225. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

Z	Isotone N = 133	Isobar A = 225
80	²¹³Hg
81	²¹⁴Tl
82	²¹⁵Pb
83	²¹⁶Bi
84	²¹⁷Po	²²⁵Po
85	²¹⁸At	²²⁵At
86	²¹⁹Rn	²²⁵Rn
87	²²⁰Fr	²²⁵Fr
88	²²¹Ra	²²⁵Ra
89	²²²Ac	²²⁵Ac
90	²²³Th	²²⁵Th
91	²²⁴Pa	²²⁵Pa
92	²²⁵U	²²⁵U
93	²²⁶Np	²²⁵Np