Astatine-211
Properties and data of the isotope 211At.
Astatine-211 is the radioisotope of the element astatine, whose atomic nucleus has 126 neutrons in addition to the element-specific 85 protons; this results in a mass number of 211: 211At.
See also: List of individual Astatine isotopes (and general data sources).
General data
Name of the isotope:Astatine-211; At-211Symbol:211At or 21185AtMass number A:211 (= number of nucleons)Atomic number Z:85 (= number of protons)Neutrons N:126Nucleon pairing (Z - N):odd - evenNuclear ratio (N/Z ratio):1.4823529411765 (= neutron-proton ratio)Neutron excess (N-Z):41Isotopic mass:210.9874961(29) u (atomic weight of Astatine-211)Nuclide 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)Separation energy:SN = 7.746(8) MeV (first neutron)
SP = 2.9831(25) MeV (first proton)Half-life:7.214(7) hDecay constant λ:2.668989236053 × 10-5 s-1Specific activity α:7.653823396746 × 10+16 Bq g-1
2068600.9180395 Ci g-1Spin and parity:
(nuclear angular momentum)9/2-Year of discovery:1940
Radioactive Decay
Half-life T½ = 7.214(7) h (hours) respectively 2.59704 × 104 seconds s.
Decay
mode | Daughter | Probability | Decay energy | γ energy
(intensity) |
|---|
| α | 207Bi | 41.80(8) % | 5.9824(13) MeV | |
| EC | 211Po | 58.20(8) % | 0.785(3) MeV | |
Parent Nuclides
Direct parent isotopes are: 215Fr, 211Rn.
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 |
|---|
| 211mAt | 4814.5(5) keV | 4.23(7) μs | (39/2-) |
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-211. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.
| Z | 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 | |
External data and identifiers
Last update: 2023-04-15
Perma link: https://www.chemlin.org/isotope/astatine-211
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