Radon-203m

Properties and data of the isotope ²⁰³Rn.

Content

General data

Name of the isotope:Radon-203m; Rn-203mSymbol:²⁰³Rn or 20386RnMass number A:203 (= number of nucleons)Atomic number Z:86 (= number of protons)Neutrons N:117Isotopic mass:202.993394(2) u (atomic weight of Radon-203m)
Excitation energy: 362(5) keVNuclide mass:202.9462218 u (calculated nuclear mass without electrons)Mass excess:-6.15345 MeVMass defect:1.693353924 u (per nucleus)Nuclear binding energy:1577.34902008 MeV (per nucleus)
7.77019222 MeV (average binding energy per nucleon)Half-life:26.9(5) sDecay constant λ:0.025767553180667 s^-1Specific activity α:7.681972023261 × 10⁺¹⁹ Bq g^-1
2076208654.9356 Ci g^-1Spin and parity:
(nuclear angular momentum)(13/2+)

Radioactive Decay

Half-life T_½ = 26.9(5) s respectively 2.69 × 10¹ seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
α	¹⁹⁹Po	75(10) %
EE/β⁺	²⁰³At	25(10) %

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
²⁰³Rn		44(2) s	(3/2-)

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 117) and isobaric (same nucleon number A = 203) with Radon-203m. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

OZ	Isotone N = 117	Isobar A = 203
71	¹⁸⁸Lu
72	¹⁸⁹Hf
73	¹⁹⁰Ta
74	¹⁹¹W
75	¹⁹²Re
76	¹⁹³Os	²⁰³Os
77	¹⁹⁴Ir	²⁰³Ir
78	¹⁹⁵Pt	²⁰³Pt
79	¹⁹⁶Au	²⁰³Au
80	¹⁹⁷Hg	²⁰³Hg
81	¹⁹⁸Tl	²⁰³Tl
82	¹⁹⁹Pb	²⁰³Pb
83	²⁰⁰Bi	²⁰³Bi
84	²⁰¹Po	²⁰³Po
85	²⁰²At	²⁰³At
86	²⁰³Rn	²⁰³Rn
87	²⁰⁴Fr	²⁰³Fr
88	²⁰⁵Ra	²⁰³Ra
89	²⁰⁶Ac
90	²⁰⁷Th