Astatine-218
Properties and data of the isotope 218At.
Astatine-218 is the radioisotope of the chemical element Astatine, which, in addition to the element-specific 85 protons, has 133 neutrons in the atomic nucleus, resulting in the mass number 218. The very short-lived, only artificially producible, unstable and therefore radioactive nuclide has no practical significance; dealing with 218At is for academic purposes only.
See also: list of Astatine isotopes.
General data
Name of the isotope:Astatine-218; At-218Symbol:218At or 21885AtMass number A:218 (= number of nucleons)Atomic number Z:85 (= number of protons)Neutrons N:133Isotopic mass:218.008696(12) u (atomic weight of Astatine-218)Nuclide mass:217.9620723 u (calculated nuclear mass without electrons)Mass excess:8.10027 MeVMass defect:1.808865548 u (per nucleus)Nuclear binding energy:1684.94740477 MeV (per nucleus)
7.72911654 MeV (average binding energy per nucleon)Separation energy:SN = 4.366(12) MeV (first neutron)
SP = 5.074(13) MeV (first proton)Half-life:1.28(6) sDecay constant λ:0.54152123481246 s-1Specific activity α:1.495925300315 × 10+21 Bq g-1
40430413522.038 Ci g-1Spin and parity:
(nuclear angular momentum)(3-.2-)Year of discovery:1943
Radioactive Decay
Half-life T½ = 1.28(6) s.
| Decay mode | Daughter | Probability | Decay energy | γ energy
(intensity) |
|---|
| α | 214Bi | 99.95(5) % | 6.8761(26) MeV | |
| β- | 218Rn | 0.05(5) % | 2.883(12) MeV | |
Parent Nuclides
Direct parent isotope is: 218Po.
Isotones and Isobars
The following table shows the atomic nuclei that are isotonic (same neutron number N = 133) and isobaric (same nucleon number A = 218) with Astatine-218. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.
| OZ | Isotone N = 133 | Isobar A = 218 |
|---|
| 80 | 213Hg | |
| 81 | 214Tl | |
| 82 | 215Pb | 218Pb |
| 83 | 216Bi | 218Bi |
| 84 | 217Po | 218Po |
| 85 | 218At | 218At |
| 86 | 219Rn | 218Rn |
| 87 | 220Fr | 218Fr |
| 88 | 221Ra | 218Ra |
| 89 | 222Ac | 218Ac |
| 90 | 223Th | 218Th |
| 91 | 224Pa | 218Pa |
| 92 | 225U | 218U |
| 93 | 226Np | |
External data and identifiers
Last update: 2023-05-18
Perma link: https://www.chemlin.org/isotope/astatine-218
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