Astatine-205m

Properties and data of the isotope ^205mAt.

Contents

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

General data

Name of the isotope:Astatine-205m; At-205mSymbol:^205mAt or 205m85AtMass number A:205 (= number of nucleons)Atomic number Z:85 (= number of protons)Neutrons N:120Excitation energy:2339.65(23) keVIsotopic mass:204.986074(16) u (atomic weight of Astatine-205m)Nuclide mass:204.9394503 u (calculated nuclear mass without electrons)Mass excess:-12.97199 MeVMass defect:1.71884364 u (per nucleus)Nuclear binding energy:1601.0925376 MeV (per nucleus)
7.8102075 MeV (average binding energy per nucleon)Half-life:7.76(14) μsDecay constant λ:89323.090278343 s^-1Specific activity α:2.636844273044 × 10⁺²⁶ Bq g^-1
7.12660614336 × 10⁺¹⁵ Ci g^-1Spin and parity:
(nuclear angular momentum)29/2+

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
²⁰⁵At		26.9(8) min	9/2-

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 120) and isobaric (same nucleon number A = 205) with Astatine-205m. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

Z	Isotone N = 120	Isobar A = 205
73	¹⁹³Ta
74	¹⁹⁴W
75	¹⁹⁵Re
76	¹⁹⁶Os
77	¹⁹⁷Ir	²⁰⁵Ir
78	¹⁹⁸Pt	²⁰⁵Pt
79	¹⁹⁹Au	²⁰⁵Au
80	²⁰⁰Hg	²⁰⁵Hg
81	²⁰¹Tl	²⁰⁵Tl
82	²⁰²Pb	²⁰⁵Pb
83	²⁰³Bi	²⁰⁵Bi
84	²⁰⁴Po	²⁰⁵Po
85	²⁰⁵At	²⁰⁵At
86	²⁰⁶Rn	²⁰⁵Rn
87	²⁰⁷Fr	²⁰⁵Fr
88	²⁰⁸Ra	²⁰⁵Ra
89	²⁰⁹Ac	²⁰⁵Ac
90	²¹⁰Th