Astatine-200

Properties and data of the isotope ²⁰⁰At.

Contents

General data

Name of the isotope:Astatine-200; At-200Symbol:²⁰⁰At or 20085AtMass number A:200 (= number of nucleons)Atomic number Z:85 (= number of protons)Neutrons N:115Isotopic mass:199.990351(26) u (atomic weight of Astatine-200)Nuclide mass:199.9437273 u (calculated nuclear mass without electrons)Mass excess:-8.98799 MeVMass defect:1.67124206 u (per nucleus)Nuclear binding energy:1556.75195144 MeV (per nucleus)
7.78375976 MeV (average binding energy per nucleon)Separation energy:S_N = 8.236(25) MeV (first neutron)
S_P = 1.97(3) MeV (first proton)Half-life:43(1) sDecay constant λ:0.016119701873487 s^-1Specific activity α:4.878146497604 × 10⁺¹⁹ Bq g^-1
1318417972.3255 Ci g^-1Spin and parity:
(nuclear angular momentum)(3+)Year of discovery:1963

Radioactive Decay

Half-life T_½ = 43(1) s respectively 4.3 × 10¹ seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
α	¹⁹⁶Bi	52(3) %	6.5962(13) MeV
EC/β⁺	²⁰⁰Po	48(3) %	7.954(26) MeV

Parent Nuclides

Direct parent isotope is: ²⁰⁴Fr.

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
^200m1At	112(5) keV	47(1) s	(7+)
^200m2At	344(5) keV	ca. 7.3 s	(10-)

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 115) and isobaric (same nucleon number A = 200) with Astatine-200. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

Z	Isotone N = 115	Isobar A = 200
70	¹⁸⁵Yb
71	¹⁸⁶Lu
72	¹⁸⁷Hf
73	¹⁸⁸Ta
74	¹⁸⁹W
75	¹⁹⁰Re
76	¹⁹¹Os	²⁰⁰Os
77	¹⁹²Ir	²⁰⁰Ir
78	¹⁹³Pt	²⁰⁰Pt
79	¹⁹⁴Au	²⁰⁰Au
80	¹⁹⁵Hg	²⁰⁰Hg
81	¹⁹⁶Tl	²⁰⁰Tl
82	¹⁹⁷Pb	²⁰⁰Pb
83	¹⁹⁸Bi	²⁰⁰Bi
84	¹⁹⁹Po	²⁰⁰Po
85	²⁰⁰At	²⁰⁰At
86	²⁰¹Rn	²⁰⁰Rn
87	²⁰²Fr	²⁰⁰Fr
88	²⁰³Ra
89	²⁰⁴Ac