Isotopes of astatine
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Astatine (85At) has 41 known isotopes, all of which are radioactive, whose mass numbers range from 188 to 229 except 189; they are accompanied by almost as many metastable excited states. The longest-lived isotope is 210At, which has a half-life of 8.1 hours, followed by the medically useful 211At, with a half-life of 7.214 hours. The longest-lived isomer is 202m1At with a half-life of just over 3 minutes. However, the longest-lived isotope existing in naturally occurring decay chains is 219At with a half-life of only 56 seconds.
List of isotopes
| Nuclide | Z | N | Isotopic mass (Da) | Discovery year | Half-life | Decay mode | Daughter isotope | Spin and parity | Isotopic abundance |
|---|---|---|---|---|---|---|---|---|---|
| Excitation energy | |||||||||
| 188At | 85 | 103 | 190+350 −80 μs | α (~50%) | 184Bi | ||||
| p (~50%) | 187Po | ||||||||
| 190At | 85 | 105 | 1.0+1.4 −0.4 ms | α | 186Bi | (10−) | |||
| 191At | 85 | 106 | 191.004148(17) | 2.1(8) ms | α | 187Bi | 1/2+ | ||
| 191mAt | 58(20) keV | 2.2(4) ms | α | 187Bi | (7/2−) | ||||
| 192At | 85 | 107 | 192.003141(3) | 11.5(6) ms | α | 188Bi | 3+# | ||
| 192mAt | 0(40) keV | 88(6) ms | α | 188mBi | (9−, 10−) | ||||
| 193At | 85 | 108 | 192.999928(23) | 29(5) ms | α | 189Bi | 1/2+ | ||
| 193m1At | 8(9) keV | 21(5) ms | α | 189m1Bi | 7/2− | ||||
| 193m2At | 42(9) keV | 28(4) ms | IT (76%) | 193At | 13/2+ | ||||
| α (24%) | 189m2Bi | ||||||||
| 194At | 85 | 109 | 193.999231(25) | 286(7) ms | α (91.7%#) | 190Bi | (5−) | ||
| β+ (8.3%#) | 194Po | ||||||||
| β+, SF (0.032%#) | (various) | ||||||||
| 194mAt | −20(40) keV | 323(7) ms | α (91.7%#) | 190Bi | 10− | ||||
| β+ (8.3%#) | 194Po | ||||||||
| β+, SF (0.032%#) | (various) | ||||||||
| 195At | 85 | 110 | 194.996274(10) | 290(20) ms | α | 191mBi | 1/2+ | ||
| β+ ? | 195Po | ||||||||
| 195mAt | 29(7) keV | 143(3) ms | α (88%) | 191Bi | 7/2- | ||||
| IT (12%) | 195At | ||||||||
| β+? | 195Po | ||||||||
| 196At | 85 | 111 | 195.99580(3) | 377(4) ms | α (97.5%) | 192Bi | (3+) | ||
| β+ (2.5%) | 196Po | ||||||||
| β+, SF (0.009%) | (various) | ||||||||
| 196m1At | −40(40) keV | (1996) | 20# ms | α | 192mBi | 10−# | |||
| 196m2At | 157.9(1) keV | 11(2) μs | IT | 196At | (5+) | ||||
| 197At | 85 | 112 | 196.993177(9) | 388.2(56) ms | α (96.1%) | 193Bi | 9/2− | ||
| β+ (3.9%) | 197Po | ||||||||
| 197m1At | 45(8) keV | 2.0(2) s | α | 193m1Bi | 1/2+ | ||||
| IT (<0.004%) | 197At | ||||||||
| β+? | 197Po | ||||||||
| 197m2At | 310.7(2) keV | 1.3(2) μs | IT | 197At | 13/2+ | ||||
| 198At | 85 | 113 | 197.992798(5) | 4.47(5) s | α (97%) | 194Bi | 3+ | ||
| β+ (3%) | 198Po | ||||||||
| 198mAt | 266.6(27) keV | 1.23(5) s | α (93%) | 10− | |||||
| β+ ? | 198Po | ||||||||
| IT ? | 198Po | ||||||||
| 199At | 85 | 114 | 198.990528(6) | 7.02(12) s | α (89%) | 195Bi | 9/2− | ||
| β+ (11%) | 199Po | ||||||||
| 199m1At | 244.0(10) keV | 273(9) ms | IT (99%) | 1/2+ | |||||
| α (1%) | 195Bi | ||||||||
| 199m2At | 572.9(1) keV | (2000) | 70(20) ns | IT | 13/2+ | ||||
| 199m3At | 2293.4(5) keV | 800(50) ns | IT | (29/2+) | |||||
| 200At | 85 | 115 | 199.990351(26) | 43.2(9) s | α (52%) | 196Bi | (3+) | ||
| β+ (48%) | 200Po | ||||||||
| 200m1At | 112.9(29) keV | 47(1) s | β+ (57%) | 200Po | (7+) | ||||
| α (43%) | 196Bi | ||||||||
| IT ? | 200At | ||||||||
| 200m2At | 343.8(30) keV | 8.0(21) s | IT ? | 200At | (10−) | ||||
| α (10.5%) | 196Bi | ||||||||
| β+ ? | 200Po | ||||||||
| 201At | 85 | 116 | 200.988417(9) | 85.2(16) s | α (71%) | 197Bi | 9/2− | ||
| β+ (29%) | 201Po | ||||||||
| 201m1At | 459(1) keV | 45(3) ms | IT | 1/2+ | |||||
| 201m2At | 459(1) keV | 3.39(9) μs | IT | 29/2+ | |||||
| 202At | 85 | 117 | 201.988626(30) | 184(1) s | β+ (88%) | 202Po | 3+ | ||
| α (12%) | 198Bi | ||||||||
| 202m1At | 190(40) keV | 182(2) s | β+ (91.5%) | 202Po | 7+ | ||||
| α (8.5%) | 198Bi | ||||||||
| IT ? | 202At | ||||||||
| 202m2At | 590(40) keV | 460(50) ms | IT (99.904%) | 202At | 10− | ||||
| α (0.096%) | 198Bi | ||||||||
| IT ? | 202At | ||||||||
| 203At | 85 | 118 | 202.986943(11) | 7.4(2) min | β+ (69%) | 203Po | 9/2− | ||
| α (31%) | 199Bi | ||||||||
| 203m1At | 683.4(3) keV | 3.5(6) ms | IT | 1/2+ | |||||
| 203m2At | 2330.1(4) keV | 9.77(21) μs | IT | 29/2+ | |||||
| 204At | 85 | 119 | 203.987251(24) | 9.12(11) min | β+ (96.2%) | 204Po | 7+ | ||
| α (3.8%) | 200Bi | ||||||||
| 204mAt | 587.30(20) keV | 108(10) ms | IT | 204At | 10− | ||||
| 205At | 85 | 120 | 204.986061(13) | 26.9(8) min | β+ (90%) | 205Po | 9/2− | ||
| α (10%) | 201Bi | ||||||||
| 205mAt | 2339.64(23) keV | 7.76(14) μs | IT | 205At | 29/2+ | ||||
| 206At | 85 | 121 | 205.986646(15) | 30.6(8) min | β+ (99.1%) | 206Po | (6)+ | ||
| α (0.9%) | 202Bi | ||||||||
| 206mAt | 810(2) keV | 813(21) ns | IT | 206At | (10)− | ||||
| 207At | 85 | 122 | 206.985800(13) | 1.81(3) h | β+ (~90%) | 207Po | 9/2− | ||
| α (~10%) | 203Bi | ||||||||
| 207mAt | 2117.3(6) keV | 108(2) ns | IT | 207At | 25/2+ | ||||
| 208At | 85 | 123 | 207.986613(10) | 1.63(3) h | β+ (99.45%) | 208Po | 6+ | ||
| α (0.55%) | 204Bi | ||||||||
| 208mAt | 2276.4(18) keV | 1.5(2) μs | IT | 208At | 16- | ||||
| 209At | 85 | 124 | 208.986169(5) | 5.42(5) h | β+ (96.1%) | 209Po | 9/2− | ||
| α (3.9%) | 205Bi | ||||||||
| 209mAt | 2429.32(22) keV | 916(10) ns | IT | 209At | 29/2+ | ||||
| 210At | 85 | 125 | 209.987147(8) | 8.1(4) h | β+ (99.825%) | 210Po | (5)+ | ||
| α (0.175%) | 206Bi | ||||||||
| 210m1At | 2549.6(2) keV | 482(6) ns | IT | 210At | (15)− | ||||
| 210m2At | 4027.7(2) keV | 5.66(7) μs | IT | 210At | (19)+ | ||||
| 211At | 85 | 126 | 210.9874962(29) | 7.214(7) h | EC (58.2%) | 211Po | 9/2− | ||
| α (41.8%) | 207Bi | ||||||||
| 211mAt | 4814.5(5) keV | 4.23(7) μs | IT | 211At | (39/2-) | ||||
| 212At | 85 | 127 | 211.9907373(26) | 314(3) ms | α | 208Bi | (1−) | ||
| 212m1At | 222.9(9) keV | 119(3) ms | α | 208Bi | (9−) | ||||
| 212m2At | 4771.4(15) keV | 152(5) μs | IT | 212At | (25−) | ||||
| 213At | 85 | 128 | 212.992937(5) | 125(6) ns | α | 209Bi | 9/2− | ||
| 213m1At | 1358(23) keV | 110(17) ns | IT | 213At | 25/2-# | ||||
| 213m2At | 2998(27) keV | 45(4) μs | IT | 213At | 49/2+# | ||||
| 214At | 85 | 129 | 213.996372(4) | 558(10) ns | α | 210Bi | 1− | ||
| 214m1At | 59(9) keV | 265(30) ns | α | 210Bi | |||||
| 214m2At | 232(5) keV | 760(15) ns | α | 210mBi | 9− | ||||
| 215At | 85 | 130 | 214.998651(7) | 37(3) μs | α | 211Bi | 9/2− | Trace | |
| 216At | 85 | 131 | 216.002423(4) | 300(30) μs | α | 212Bi | 1− | ||
| 216mAt | 161(11) keV | (1971) | 100# μs | α | 212m1Bi | 9−# | |||
| 217At | 85 | 132 | 217.004718(5) | 32.6(3) ms | α (99.992%) | 213Bi | 9/2− | Trace | |
| β− (0.008%) | 217Rn | ||||||||
| 218At | 85 | 133 | 218.008696(12) | 1.28(6) s | α (~100%) | 214Bi | (2−,3−) | Trace | |
| β− (?) | 218Rn | ||||||||
| 219At | 85 | 134 | 219.011161(3) | 56(3) s | α (93.6%) | 215Bi | (9/2−) | Trace | |
| β− (6.4%) | 219Rn | ||||||||
| 220At | 85 | 135 | 220.015433(15) | 3.71(4) min | β− (92%) | 220Rn | 3(−#) | ||
| α (8%) | 216Bi | ||||||||
| 221At | 85 | 136 | 221.018017(15) | 2.3(2) min | β− | 221Rn | 3/2−# | ||
| 222At | 85 | 137 | 222.022494(17) | 54(10) s | β− | 222Rn | |||
| 223At | 85 | 138 | 223.025151(15) | 50(7) s | β− | 223Rn | 3/2−# | ||
| 224At | 85 | 139 | 224.029749(24) | 2.5 +/- 1.5 min | β− | 224Rn | 2+# | ||
| 225At | 85 | 140 | 225.03253(32)# | 3# s (>300 ns) | β− ? | 225Rn | 1/2+# | ||
| 226At | 85 | 141 | 226.03721(32)# | 7# min (>300 ns) | β− ? | 226Rn | 2+# | ||
| 227At | 85 | 142 | 227.04018(32)# | 5# s (>300 ns) | β− ? | 227Rn | 1/2+# | ||
| 228At | 85 | 143 | 228.04496(43)# | 1# min (>300 ns) | β− ? | 228Rn | 3+# | ||
| 229At | 85 | 144 | 229.04819(43)# | 1# s (>300 ns) | β− ? | 229Rn | 1/2+# | ||
| 230At | 85 | 145 | |||||||
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Alpha decay
| Mass number | Mass excess | Mass excess of daughter | Energy of alpha decay | Half-life | Probability of alpha decay | Alpha decay half-life |
|---|---|---|---|---|---|---|
| 195 | −3.470 MeV | −10.814 MeV | 7.344 MeV | 0.29 s | ~100% | 0.29 s |
| 196 | −3.910 MeV | −11.105 MeV | 7.195 MeV | 0.377 s | 97.5% | 0.39 s |
| 197 | −6.355 MeV | −13.460 MeV | 7.105 MeV | 0.388 s | 96.1% | 0.40 s |
| 198 | −6.709 MeV | −13.598 MeV | 6.889 MeV | 4.47 s | 97% | 4.6 s |
| 199 | −8.823 MeV | −15.601 MeV | 6.778 MeV | 7.0 s | 89% | 7.9 s |
| 200 | −8.988 MeV | −15.584 MeV | 6.596 MeV | 43.2 s | 52% | 83 s |
| 201 | −10.789 MeV | −17.262 MeV | 6.473 MeV | 85.2 s | 71% | 2.0 min |
| 202 | −10.595 MeV | −16.949 MeV | 6.354 MeV | 184 s | 12% | 2.6 min |
| 203 | −12.163 MeV | −18.373 MeV | 6.210 MeV | 7.4 min | 31% | 2.4 min |
| 204 | −11.875 MeV | −17.946 MeV | 6.071 MeV | 9.1 min | 3.8% | 4.0 h |
| 205 | −12.985 MeV | −19.004 MeV | 6.039 MeV | 26.9 min | 10% | 4.5 h |
| 206 | −12.439 MeV | −18.326 MeV | 5.887 MeV | 30.6 min | 0.90% | 2.4 d |
| 207 | −13.227 MeV | −19.100 MeV | 5.873 MeV | 1.81 h | ~10% | 18 h |
| 208 | −12.470 MeV | −18.221 MeV | 5.751 MeV | 1.63 h | 0.55% | 12.3 d |
| 209 | −12.884 MeV | −18.641 MeV | 5.757 MeV | 5.42 h | 3.9% | 5.8 d |
| 210 | −11.972 MeV | −17.603 MeV | 5.631 MeV | 8.1 h | 0.175% | 193 d |
| 211 | −11.647 MeV | −17.630 MeV | 5.983 MeV | 7.214 h | 41.80% | 17 h |
| 212 | −8.628 MeV | −16.445 MeV | 7.817 MeV | 0.314 s | % | 0.31 s |
| 213 | −6.580 MeV | −15.834 MeV | 9.254 MeV | 125 ns | 100% | 125 ns |
| 214 | −3.379 MeV | −12.367 MeV | 8.988 MeV | 0.56 μs | 100% | 0.56 μs |
| 215 | −1.257 MeV | −9.434 MeV | 8.177 MeV | 37 μs | 100% | 37 μs |
| 216 | 2.257 MeV | −5.693 MeV | 7.950 MeV | 0.3 ms | 100% | 0.3 ms |
| 217 | 4.395 MeV | −2.807 MeV | 7.202 MeV | 32.6 ms | 99.992% | 33 ms |
| 218 | 8.100 MeV | 1.224 MeV | 6.876 MeV | 1.28 s | ~100% | 1.28 s |
| 219 | 10.396 MeV | 4.054 MeV | 6.342 MeV | 56 s | 93.6% | 60 s |
| 220 | 14.376 MeV | 8.299 MeV | 6.077 MeV | 3.71 min | 8% | 46 min |
| 221 | 16.783 MeV | 11.155 MeV | 5.628 MeV | 2.3 min | experimentally alpha stable | - |
Alpha decay energy follows the same trend as for other heavy elements. The lighter astatine isotopes have quite high decay energies, which become lower as more neutrons are added, reaching a minimum at 125 neutrons (astatine-210), even though 126 (astatine-211) is the magic number. The decay energies increase much more steeply, though, on the next two steps, reaching a high at 128 neutrons where the alpha-decay product would have the magic number of 126. Here this is astatine-213, releasing the highest energy and having the shortest life (125 ns) of all the isotopes. The energy then declines again, and alpha lifetimes increase quickly, no long-lived astatine isotope exists; this happens due to the increasing role of beta decay. This decay mode is especially important for astatine: as early as 1950, it was postulated that the element has no beta-stable isotopes (i.e. ones that do not undergo beta decay at all), though nuclear mass measurements reveal that 215At is in fact beta-stable, as it has the lowest mass of all isobars with A = 215. A beta decay mode has been found for all other astatine isotopes except for 212-216At and their isomers. Among other isotopes, if they do not undergo alpha decay: astatine-210 and the lighter isotopes decay by electron capture or positron emission, 211 by electron capture only, and astatine-217 and heavier isotopes undergo β- decay. Astatine-212, 214, and 216 should be able to decay either way.
See also
Daughter products other than astatine
Notes
- Lavrukhina, Avgusta Konstantinovna; Pozdnyakov, Aleksandr Aleksandrovich (1966). Аналитическая химия технеция, прометия, астатина и франция [Analytical Chemistry of Technetium, Promethium, Astatine, and Francium] (in Russian). Nauka.