Radon-208m

Properties and data of the isotope ²⁰⁸Rn.

Content

General data

Name of the isotope:Radon-208m; Rn-208mSymbol: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-208m)
Excitation energy: 1828.3(4) keVNuclide 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)Half-life:487(12) nsDecay constant λ:1423300.1654208 s^-1Specific activity α:4.140731440645 × 10⁺²⁷ Bq g^-1
1.119116605579 × 10⁺¹⁷ Ci g^-1Spin and parity:
(nuclear angular momentum)8+Magnetic dipole moment:μ(μ_N) = 6.98(8)Quadrupole moment Q:0.39(5) barn (100 fm²)Nuclear g-factor:g_l = 0.8725

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
²⁰⁸Rn		24.35(14) min	0+

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-208m. 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