Radon-221

Properties and data of the isotope ²²¹Rn.

Contents

General Data

Radioactive Decay

Parent Nuclides

Isotones und Isobares

Literature

Radon-221 is a radioisotope of the chemical element radon, which has 135 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 221. The very short-lived, only artificially produced, unstable and thus radioactive nuclide has no practical significance; the study of ²²¹Rn is exclusively for academic purposes and scientific research.

In 1956, a report was published on the discovery of the isotope radon-221, which at that time was still called emanation-221 (Em-221 or Em²²¹) [1]. In the experiments described therein, a thorium target was bombarded with protons of an energy of 110 MeV and the resulting reaction product was chemically separated. The identification of ²²¹ was carried out on the basis of the radioactive decay products.

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

General data

Name of the isotope:Radon-221; Rn-221Symbol:²²¹Rn or 22186RnMass number A:221 (= number of nucleons)Atomic number Z:86 (= number of protons)Neutrons N:135Nucleon pairing (Z - N):even - oddNuclear ratio (N/Z ratio):1.5697674418605 (= neutron-proton ratio)Neutron excess (N-Z):49Isotopic mass:221.015536(6) u (atomic weight of Radon-221)Nuclide mass:220.9683638 u (calculated nuclear mass without electrons)Mass excess:14.47169 MeVMass defect:1.827180412 u (per nucleus)Nuclear binding energy:1702.0075907 MeV (per nucleus)
7.70139181 MeV (average binding energy per nucleon)Separation energy:S_N = 4.212(6) MeV (first neutron)
S_P = 7.193(15) MeV (first proton)Half-life:25.7(5) minDecay constant λ:0.0004495117902464 s^-1Specific activity α:1.224897429441 × 10⁺¹⁸ Bq g^-1
33105335.930857 Ci g^-1Spin and parity:
(nuclear angular momentum)7/2+Magnetic dipole moment:μ(μ_N) = - 0.020(1)Quadrupole moment Q:0.38(4) barn (100 fm²)Nuclear g-factor:g_l = -0.0057142857142857Charge radius:5.6834(199) femtometer fmYear of discovery:1956

Radioactive Decay

Half-life T_½ = 25.7(5) min (minutes) respectively 1.542 × 10³ seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
α	²¹⁷Po	22(1) %	6.163(3) MeV
β^-	²²¹Fr	78(1) %	1.194(7) MeV

Parent Nuclides

Direct parent isotope is: ²²¹At.

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 135) and isobaric (same nucleon number A = 221) with Radon-221. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

Z	Isotone N = 135	Isobar A = 221
80	²¹⁵Hg
81	²¹⁶Tl
82	²¹⁷Pb
83	²¹⁸Bi	²²¹Bi
84	²¹⁹Po	²²¹Po
85	²²⁰At	²²¹At
86	²²¹Rn	²²¹Rn
87	²²²Fr	²²¹Fr
88	²²³Ra	²²¹Ra
89	²²⁴Ac	²²¹Ac
90	²²⁵Th	²²¹Th
91	²²⁶Pa	²²¹Pa
92	²²⁷U	²²¹U
93	²²⁸Np	²²¹Np
94	²²⁹Pu
95	²³⁰Am