Astatine-211m

Properties and data of the isotope ²¹¹At.

Content

General data

Name of the isotope:Astatine-211m; At-211mSymbol:²¹¹At or 21185AtMass number A:211 (= number of nucleons)Atomic number Z:85 (= number of protons)Neutrons N:126Isotopic mass:210.9874961(29) u (atomic weight of Astatine-211m)
Excitation energy: 4814.5(5) keVNuclide mass:210.9408724 u (calculated nuclear mass without electrons)Mass excess:-11.64731 MeVMass defect:1.769411036 u (per nucleus)Nuclear binding energy:1648.19576357 MeV (per nucleus)
7.81135433 MeV (average binding energy per nucleon)Half-life:4.23(7) μsDecay constant λ:163864.58169266 s^-1Specific activity α:4.699121870989 × 10⁺²⁶ Bq g^-1
1.270032938105 × 10⁺¹⁶ Ci g^-1Spin and parity:
(nuclear angular momentum)(39/2-)Magnetic dipole moment:μ(μ_N) = 13.46(14)Quadrupole moment Q:1.91(25) barn (100 fm²)Nuclear g-factor:g_l = 0.69025641025641

Radioactive Decay

Half-life T_½ = 4.23(7) μs respectively 4.23 × 10^-6 seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
Iso	²¹¹At	100 %

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
²¹¹At		7.214(7) h	9/2-

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 126) and isobaric (same nucleon number A = 211) with Astatine-211m. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

OZ	Isotone N = 126	Isobar A = 211
76	²⁰²Os
77	²⁰³Ir
78	²⁰⁴Pt
79	²⁰⁵Au
80	²⁰⁶Hg	²¹¹Hg
81	²⁰⁷Tl	²¹¹Tl
82	²⁰⁸Pb	²¹¹Pb
83	²⁰⁹Bi	²¹¹Bi
84	²¹⁰Po	²¹¹Po
85	²¹¹At	²¹¹At
86	²¹²Rn	²¹¹Rn
87	²¹³Fr	²¹¹Fr
88	²¹⁴Ra	²¹¹Ra
89	²¹⁵Ac	²¹¹Ac
90	²¹⁶Th	²¹¹Th
91	²¹⁷Pa
92	²¹⁸U
93	²¹⁹Np