Astatine-201

Properties and data of the isotope ²⁰¹At.

Contents

General Data

Radioactive Decay

Parent Nuclides

Isotones und Isobares

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

General data

Name of the isotope:Astatine-201; At-201Symbol:²⁰¹At or 20185AtMass number A:201 (= number of nucleons)Atomic number Z:85 (= number of protons)Neutrons N:116Isotopic mass:200.988417(9) u (atomic weight of Astatine-201)Nuclide mass:200.9417933 u (calculated nuclear mass without electrons)Mass excess:-10.7895 MeVMass defect:1.681840976 u (per nucleus)Nuclear binding energy:1566.6247781 MeV (per nucleus)
7.79415312 MeV (average binding energy per nucleon)Separation energy:S_N = 9.873(26) MeV (first neutron)
S_P = 1.137(11) MeV (first proton)Half-life:85.2(16) sDecay constant λ:0.0081355302882623 s^-1Specific activity α:2.449665468309 × 10⁺¹⁹ Bq g^-1
662071748.19186 Ci g^-1Spin and parity:
(nuclear angular momentum)(9/2-)Year of discovery:1963

Radioactive Decay

Half-life T_½ = 85.2(16) s respectively 8.52 × 10¹ seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
α	¹⁹⁷Bi	71(7) %	6.4728(16) MeV
EC/β⁺	²⁰¹Po	29(7) %	5.732(10) MeV

Parent Nuclides

Direct parent isotope is: ²⁰⁵Fr.

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 116) and isobaric (same nucleon number A = 201) with Astatine-201. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

Z	Isotone N = 116	Isobar A = 201
71	¹⁸⁷Lu
72	¹⁸⁸Hf
73	¹⁸⁹Ta
74	¹⁹⁰W
75	¹⁹¹Re
76	¹⁹²Os	²⁰¹Os
77	¹⁹³Ir	²⁰¹Ir
78	¹⁹⁴Pt	²⁰¹Pt
79	¹⁹⁵Au	²⁰¹Au
80	¹⁹⁶Hg	²⁰¹Hg
81	¹⁹⁷Tl	²⁰¹Tl
82	¹⁹⁸Pb	²⁰¹Pb
83	¹⁹⁹Bi	²⁰¹Bi
84	²⁰⁰Po	²⁰¹Po
85	²⁰¹At	²⁰¹At
86	²⁰²Rn	²⁰¹Rn
87	²⁰³Fr	²⁰¹Fr
88	²⁰⁴Ra	²⁰¹Ra
89	²⁰⁵Ac