Radon-209

Properties and data of the isotope ²⁰⁹Rn.

Content

General data

Name of the isotope:Radon-209; Rn-209Symbol:²⁰⁹Rn or 20986RnMass number A:209 (= number of nucleons)Atomic number Z:86 (= number of protons)Neutrons N:123Isotopic mass:208.990401(11) u (atomic weight of Radon-209)Nuclide mass:208.9432288 u (calculated nuclear mass without electrons)Mass excess:-8.94141 MeVMass defect:1.74833642 u (per nucleus)Nuclear binding energy:1628.56488521 MeV (per nucleus)
7.79217648 MeV (average binding energy per nucleon)Separation energy:S_N = 7.357(14) MeV (first neutron)
S_P = 3.760(13) MeV (first proton)Half-life:28.8(10) minDecay constant λ:0.00040112684060182 s^-1Specific activity α:1.161366508079 × 10⁺¹⁸ Bq g^-1
31388284.002151 Ci g^-1Spin and parity:
(nuclear angular momentum)5/2-Magnetic dipole moment:μ(μ_N) = 0.8388(4)Quadrupole moment Q:0.311(31) barn (100 fm²)Nuclear g-factor:g_l = 0.33552Charge radius:5.5743(177) femtometer fmYear of discovery:1952

Radioactive Decay

Half-life T_½ = 28.8(10) min (minutes) respectively 1.728 × 10³ seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
α	²⁰⁵Po	17(2) %	6.1554(20) MeV
EE/β⁺	²⁰⁹At	83(2) %	3.943(11) MeV

Parent Nuclides

Direct parent isotopes are: ²¹³Ra, ²⁰⁹Fr.

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
^209m1Rn	1174.01(13) keV	13.4(13) μs	13/2+
^209m2Rn	3636.81(23) keV	3.0(3) μs	35/2+

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 123) and isobaric (same nucleon number A = 209) with Radon-209. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

OZ	Isotone N = 123	Isobar A = 209
74	¹⁹⁷W
75	¹⁹⁸Re
76	¹⁹⁹Os
77	²⁰⁰Ir
78	²⁰¹Pt
79	²⁰²Au	²⁰⁹Au
80	²⁰³Hg	²⁰⁹Hg
81	²⁰⁴Tl	²⁰⁹Tl
82	²⁰⁵Pb	²⁰⁹Pb
83	²⁰⁶Bi	²⁰⁹Bi
84	²⁰⁷Po	²⁰⁹Po
85	²⁰⁸At	²⁰⁹At
86	²⁰⁹Rn	²⁰⁹Rn
87	²¹⁰Fr	²⁰⁹Fr
88	²¹¹Ra	²⁰⁹Ra
89	²¹²Ac	²⁰⁹Ac
90	²¹³Th	²⁰⁹Th
91	²¹⁴Pa
92	²¹⁵U