Astatine-200m2

Properties and data of the isotope ²⁰⁰At.

Content

General data

Name of the isotope:Astatine-200m2; At-200m2Symbol: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-200m2)
Excitation energy: 344(5) keVNuclide 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)Half-life:ca. 7.3 sDecay constant λ:0.094951668569856 s^-1Specific activity α:2.873428758862 × 10⁺²⁰ Bq g^-1
7766023672.6022 Ci g^-1Spin and parity:
(nuclear angular momentum)(10-)

Radioactive Decay

Half-life T_½ = ca. 7.3 s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
α	¹⁹⁶Bi	ca. 10.5 %
Iso, EE/β⁺		89.5 %

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
²⁰⁰At		43(1) s	(3+)
^200m1At	112(5) keV	47(1) s	(7+)

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-200m2. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

OZ	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