Radon-208

Properties and data of the isotope ²⁰⁸Rn.

Content

General data

Name of the isotope:Radon-208; Rn-208Symbol:²⁰⁸Rn or 20886RnMass number A:208 (= number of nucleons)Atomic number Z:86 (= number of protons)Neutrons N:122Isotopic mass:207.989634(12) u (atomic weight of Radon-208)Nuclide mass:207.9424618 u (calculated nuclear mass without electrons)Mass excess:-9.65587 MeVMass defect:1.740438504 u (per nucleus)Nuclear binding energy:1621.20802385 MeV (per nucleus)
7.79426935 MeV (average binding energy per nucleon)Separation energy:S_N = 9.092(14) MeV (first neutron)
S_P = 3.717(17) MeV (first proton)Half-life:24.35(14) minDecay constant λ:0.00047443338847361 s^-1Specific activity α:1.380243813548 × 10⁺¹⁸ Bq g^-1
37303886.852659 Ci g^-1Spin and parity:
(nuclear angular momentum)0+Charge radius:5.5725(177) femtometer fmYear of discovery:1955

Radioactive Decay

Half-life T_½ = 24.35(14) min (minutes) respectively 1.461 × 10³ seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
α	²⁰⁴Po	62(7) %	6.2607(17) MeV
EE/β⁺	²⁰⁸At	38(7) %	2.814(14) MeV

Parent Nuclides

Direct parent isotopes are: ²¹²Ra, ²⁰⁸Fr.

Nuclear Isomers

Nuclear isomers or excited states with the activation energy in keV related to the ground state.

Nuclear Isomer	Excitation Energy	Half-life	Spin
^208mRn	1828.3(4) keV	487(12) ns	8+

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 122) and isobaric (same nucleon number A = 208) with Radon-208. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

OZ	Isotone N = 122	Isobar A = 208
74	¹⁹⁶W
75	¹⁹⁷Re
76	¹⁹⁸Os
77	¹⁹⁹Ir
78	²⁰⁰Pt	²⁰⁸Pt
79	²⁰¹Au	²⁰⁸Au
80	²⁰²Hg	²⁰⁸Hg
81	²⁰³Tl	²⁰⁸Tl
82	²⁰⁴Pb	²⁰⁸Pb
83	²⁰⁵Bi	²⁰⁸Bi
84	²⁰⁶Po	²⁰⁸Po
85	²⁰⁷At	²⁰⁸At
86	²⁰⁸Rn	²⁰⁸Rn
87	²⁰⁹Fr	²⁰⁸Fr
88	²¹⁰Ra	²⁰⁸Ra
89	²¹¹Ac	²⁰⁸Ac
90	²¹²Th	²⁰⁸Th
91	²¹³Pa
92	²¹⁴U