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.

Quick facts Main isotopes, Decay ...
Isotopes of astatine (85At)
Main isotopes[1] Decay
Isotope abun­dance half-life (t1/2) mode pro­duct
207At synth 1.81 h β+90% 207Po
α10% 203Bi
208At synth 1.63 h β+99.5% 208Po
α0.55% 204Bi
209At synth 5.41 h β+96.1% 209Po
α3.9% 205Bi
210At synth 8.1 h β+99.8% 210Po
α0.175% 206Bi
211At synth 7.214 h ε58.2% 211Po
α41.8% 207Bi
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List of isotopes


More information Nuclide, Z ...
Nuclide
[n 1]		 Z N Isotopic mass (Da)[2]
[n 2][n 3]		 Discovery
year[3][4]		 Half-life[1]
 Decay
mode[1]
[n 4]		 Daughter
isotope
[n 5]		 Spin and
parity[1]
[n 6][n 7]		 Isotopic
abundance
Excitation energy[n 7]
188At[5] 85 103 2025 190+350
−80 μs		 α (~50%) 184Bi
p (~50%) 187Po
190At[6] 85 105 2023 1.0+1.4
−0.4 ms		 α 186Bi (10−)
191At 85 106 191.004148(17) 2003 2.1(8) ms α 187Bi 1/2+
191mAt 58(20) keV 2003 2.2(4) ms α 187Bi (7/2−)
192At 85 107 192.003141(3) 2006 11.5(6) ms α 188Bi 3+#
192mAt[n 8] 0(40) keV 2006 88(6) ms α 188mBi (9−, 10−)
193At 85 108 192.999928(23) 2003 29(5) ms α 189Bi 1/2+
193m1At[n 8] 8(9) keV 2003 21(5) ms α 189m1Bi 7/2−
193m2At 42(9) keV 2003 28(4) ms IT (76%) 193At 13/2+
α (24%) 189m2Bi
194At 85 109 193.999231(25) 2009 286(7) ms α (91.7%#) 190Bi (5−)
β+ (8.3%#) 194Po
β+, SF (0.032%#) (various)
194mAt[n 8] −20(40) keV 2009 323(7) ms α (91.7%#) 190Bi 10−
β+ (8.3%#) 194Po
β+, SF (0.032%#) (various)
195At 85 110 194.996274(10) 1999 290(20) ms α 191mBi 1/2+
β+ ? 195Po
195mAt 29(7) keV 1999 143(3) ms α (88%) 191Bi 7/2-
IT (12%) 195At
β+? 195Po
196At 85 111 195.99580(3) 1967 377(4) ms α (97.5%) 192Bi (3+)
β+ (2.5%) 196Po
β+, SF (0.009%) (various)
196m1At[n 8] −40(40) keV (1996)[n 9] 20# ms α 192mBi 10−#
196m2At 157.9(1) keV 2000 11(2) μs IT 196At (5+)
197At 85 112 196.993177(9) 1967 388.2(56) ms α (96.1%) 193Bi 9/2−
β+ (3.9%) 197Po
197m1At 45(8) keV 1986 2.0(2) s α 193m1Bi 1/2+
IT (<0.004%) 197At
β+? 197Po
197m2At 310.7(2) keV 1999 1.3(2) μs IT 197At 13/2+
198At 85 113 197.992798(5) 1967 4.47(5) s α (97%) 194Bi 3+
β+ (3%) 198Po
198mAt 266.6(27) keV 1967 1.23(5) s α (93%) 10−
β+ ? 198Po
IT ? 198Po
199At 85 114 198.990528(6) 1967 7.02(12) s α (89%) 195Bi 9/2−
β+ (11%) 199Po
199m1At 244.0(10) keV 2013 273(9) ms IT (99%) 1/2+
α (1%) 195Bi
199m2At 572.9(1) keV (2000)[n 10] 70(20) ns IT 13/2+
199m3At 2293.4(5) keV 2010 800(50) ns IT (29/2+)
200At 85 115 199.990351(26) 1963 43.2(9) s α (52%) 196Bi (3+)
β+ (48%) 200Po
200m1At 112.9(29) keV 1992 47(1) s β+ (57%) 200Po (7+)
α (43%) 196Bi
IT ? 200At
200m2At 343.8(30) keV 1967 8.0(21) s IT ? 200At (10−)
α (10.5%) 196Bi
β+ ? 200Po
201At 85 116 200.988417(9) 1963 85.2(16) s α (71%) 197Bi 9/2−
β+ (29%) 201Po
201m1At 459(1) keV 2014 45(3) ms IT 1/2+
201m2At 459(1) keV 2015 3.39(9) μs IT 29/2+
202At 85 117 201.988626(30) 1961 184(1) s β+ (88%) 202Po 3+
α (12%) 198Bi
202m1At 190(40) keV 1992 182(2) s β+ (91.5%) 202Po 7+
α (8.5%) 198Bi
IT ? 202At
202m2At 590(40) keV 1992 460(50) ms IT (99.904%) 202At 10−
α (0.096%) 198Bi
IT ? 202At
203At 85 118 202.986943(11) 1951 7.4(2) min β+ (69%) 203Po 9/2−
α (31%) 199Bi
203m1At 683.4(3) keV 2017 3.5(6) ms IT 1/2+
203m2At 2330.1(4) keV 2018 9.77(21) μs IT 29/2+
204At 85 119 203.987251(24) 1961 9.12(11) min β+ (96.2%) 204Po 7+
α (3.8%) 200Bi
204mAt 587.30(20) keV 1975 108(10) ms IT 204At 10−
205At 85 120 204.986061(13) 1951 26.9(8) min β+ (90%) 205Po 9/2−
α (10%) 201Bi
205mAt 2339.64(23) keV 1982 7.76(14) μs IT 205At 29/2+
206At 85 121 205.986646(15) 1961 30.6(8) min β+ (99.1%) 206Po (6)+
α (0.9%) 202Bi
206mAt 810(2) keV 1999 813(21) ns IT 206At (10)−
207At 85 122 206.985800(13) 1951 1.81(3) h β+ (~90%) 207Po 9/2−
α (~10%) 203Bi
207mAt 2117.3(6) keV 1978 108(2) ns IT 207At 25/2+
208At 85 123 207.986613(10) 1950 1.63(3) h β+ (99.45%) 208Po 6+
α (0.55%) 204Bi
208mAt 2276.4(18) keV 1984 1.5(2) μs IT 208At 16-
209At 85 124 208.986169(5) 1951 5.42(5) h β+ (96.1%) 209Po 9/2−
α (3.9%) 205Bi
209mAt 2429.32(22) keV 1975 916(10) ns IT 209At 29/2+
210At 85 125 209.987147(8) 1949 8.1(4) h β+ (99.825%) 210Po (5)+
α (0.175%) 206Bi
210m1At 2549.6(2) keV 1972 482(6) ns IT 210At (15)−
210m2At 4027.7(2) keV 1978 5.66(7) μs IT 210At (19)+
211At 85 126 210.9874962(29) 1940 7.214(7) h EC (58.2%) 211Po 9/2−
α (41.8%) 207Bi
211mAt 4814.5(5) keV 1971 4.23(7) μs IT 211At (39/2-)
212At 85 127 211.9907373(26) 1954 314(3) ms α[n 11] 208Bi (1−)
212m1At 222.9(9) keV 1963 119(3) ms α 208Bi (9−)
212m2At 4771.4(15) keV 1998 152(5) μs IT 212At (25−)
213At 85 128 212.992937(5) 1968 125(6) ns α[n 12] 209Bi 9/2−
213m1At 1358(23) keV 1980 110(17) ns IT 213At 25/2-#
213m2At 2998(27) keV 2013 45(4) μs IT 213At 49/2+#
214At 85 129 213.996372(4) 1949 558(10) ns α 210Bi 1−
214m1At 59(9) keV 1982 265(30) ns α 210Bi
214m2At 232(5) keV 1982 760(15) ns α 210mBi[9] 9−
215At 85 130 214.998651(7) 1944 37(3) μs α 211Bi 9/2− Trace[n 13]
216At 85 131 216.002423(4) 1948 300(30) μs α[n 14] 212Bi 1−
216mAt 161(11) keV (1971)[n 9] 100# μs α 212m1Bi[11] 9−#
217At 85 132 217.004718(5) 1947 32.6(3) ms α (99.992%) 213Bi 9/2− Trace[n 15]
β− (0.008%) 217Rn
218At 85 133 218.008696(12) 1939 1.28(6) s α (~100%) 214Bi (2−,3−) Trace[n 16]
β− (?) 218Rn
219At 85 134 219.011161(3) 1953 56(3) s α (93.6%) 215Bi (9/2−) Trace[n 13]
β− (6.4%) 219Rn
220At 85 135 220.015433(15) 1989 3.71(4) min β− (92%) 220Rn 3(−#)
α (8%) 216Bi
221At 85 136 221.018017(15) 1989 2.3(2) min β− 221Rn 3/2−#
222At 85 137 222.022494(17) 1989 54(10) s β− 222Rn
223At 85 138 223.025151(15) 1989 50(7) s β− 223Rn 3/2−#
224At 85 139 224.029749(24) 2010 2.5 +/- 1.5 min β− 224Rn 2+#
225At 85 140 225.03253(32)# 2010 3# s (>300 ns) β− ? 225Rn 1/2+#
226At 85 141 226.03721(32)# 2010 7# min (>300 ns) β− ? 226Rn 2+#
227At 85 142 227.04018(32)# 2010 5# s (>300 ns) β− ? 227Rn 1/2+#
228At 85 143 228.04496(43)# 2010 1# min (>300 ns) β− ? 228Rn 3+#
229At 85 144 229.04819(43)# 2010 1# s (>300 ns) β− ? 229Rn 1/2+#
230At 85 145
This table header & footer:
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  1. [1]
    mAt – Excited nuclear isomer.
  2. [2]
    ( ) – Uncertainty (1σ) is given in concise form in parentheses after the corresponding last digits.
  3. [3]
    # – Atomic mass marked #: value and uncertainty derived not from purely experimental data, but at least partly from trends from the Mass Surface (TMS).
  4. [4]
    Modes of decay:
    EC:Electron capture
    IT:Isomeric transition
  5. [5]
    Bold italics symbol as daughter – Daughter product is nearly stable.
  6. [6]
    ( ) spin value – Indicates spin with weak assignment arguments.
  7. [7]
    # – Values marked # are not purely derived from experimental data, but at least partly from trends of neighboring nuclides (TNN).
  8. [8]
    Order of ground state and isomer is uncertain.
  9. [9]
    Half-life not measured, not included in discovery database
  10. [10]
    Half-life shorter than 100ns, not included in discovery database
  11. [11]
    Theoretically capable of β+ decay to 212Po or β− decay to 212Rn; the branching ratios are expected to be <3×10−2% and <2×10−6% (partial half-lives >17.4 min and >182 d) respectively.[7]
  12. [12]
    Theoretically capable of electron capture to 213Po; the branching ratio is expected to be <2.5×10−12% (partial half-life >57.9 d).[8]
  13. [13]
    Intermediate decay product of 235U
  14. [14]
    Theoretically capable of electron capture to 216Po or β− decay to 216Rn; the branching ratios are expected to be <3×10−7% and <6×10−3% (partial half-lives >1.2 d and >5.0 s) respectively.[10]
  15. [15]
    Intermediate decay product of 237Np
  16. [16]
    Intermediate decay product of 238U

Alpha decay

More information Mass number, Mass excess ...
Alpha decay characteristics for astatine isotopes, with all nuclear data from NUBASE2020.[1][a]
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 -
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Alpha decay energy follows the same trend as for other heavy elements.[12] 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.[12] 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),[13] though nuclear mass measurements reveal that 215At is in fact beta-stable, as it has the lowest mass of all isobars with A = 215.[1] A beta decay mode has been found for all other astatine isotopes except for 212-216At and their isomers.[1] 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

  1. [a]
    In the table, under the words "mass excess", the energy equivalents are given rather than the real mass excesses; "mass excess of daughter" stands for the energy equivalent of the mass excess sum of the daughter of the isotope and the alpha particle; "alpha decay half-life" refers to the half-life if decay modes other than alpha are omitted.

References

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