Radon-225

Properties and data of the isotope ²²⁵Rn.

Contents

Radon-225 is a radioisotope of the chemical element radon, which has 139 neutrons in its atomic nucleus in addition to the element-specific 86 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 ²²⁵Rn is exclusively for academic purposes.

The first report on the isotope radon-225 appeared in 1969. In the experiment described in this study, a molten Sn template was irradiated with a 600 MeV proton beam from the CERN synchrocyclotron, producing, among other isotopes, the short-lived nuclide ²²⁵Rn [1].

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

General data

Name of the isotope:Radon-225; Rn-225Symbol:²²⁵Rn or 22586RnMass number A:225 (= number of nucleons)Atomic number Z:86 (= number of protons)Neutrons N:139Nucleon pairing (Z - N):even - oddNuclear ratio (N/Z ratio):1.6162790697674 (= neutron-proton ratio)Neutron excess (N-Z):53Isotopic mass:225.028486(12) u (atomic weight of Radon-225)Nuclide mass:224.9813138 u (calculated nuclear mass without electrons)Mass excess:26.53454 MeVMass defect:1.848890076 u (per nucleus)Nuclear binding energy:1722.23001245 MeV (per nucleus)
7.65435561 MeV (average binding energy per nucleon)Separation energy:S_N = 3.982(15) MeV (first neutron)
S_P = 8.466(25) MeV (first proton)Half-life:4.66(4) minDecay constant λ:0.0024790671693846 s^-1Specific activity α:6.635240753457 × 10⁺¹⁸ Bq g^-1
179330831.17452 Ci g^-1Spin and parity:
(nuclear angular momentum)7/2-Magnetic dipole moment:μ(μ_N) = - 0.696(8)Quadrupole moment Q:0.84 barn (100 fm²)Nuclear g-factor:g_l = -0.19885714285714Year of discovery:1969

Radioactive Decay

Half-life T_½ = 4.66(4) min (minutes) respectively 2.796 × 10² seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
β^-	²²⁵Fr	100 %	2.714(16) MeV

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 139) and isobaric (same nucleon number A = 225) with Radon-225. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

Z	Isotone N = 139	Isobar A = 225
83	²²²Bi
84	²²³Po	²²⁵Po
85	²²⁴At	²²⁵At
86	²²⁵Rn	²²⁵Rn
87	²²⁶Fr	²²⁵Fr
88	²²⁷Ra	²²⁵Ra
89	²²⁸Ac	²²⁵Ac
90	²²⁹Th	²²⁵Th
91	²³⁰Pa	²²⁵Pa
92	²³¹U	²²⁵U
93	²³²Np	²²⁵Np
94	²³³Pu
95	²³⁴Am
96	²³⁵Cm
97	²³⁶Bk
98	²³⁷Cf