Francium (87Fr) has no stable isotopes, thus a standard atomic weight cannot be given. Its most stable isotope is 223Fr with a half-life of 22 minutes, occurring in trace quantities in nature as an intermediate decay product of 235U.
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Of elements whose most stable isotopes have been identified with certainty, francium is the most unstable. All elements with atomic number of 106 (seaborgium) or greater have most-stable-known isotopes shorter than that of francium, but as those elements have only a relatively small number of isotopes discovered, the possibility remains that undiscovered isotopes of these elements may have longer half-lives.
List of isotopes
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| Nuclide [n 1] |
Historic name |
Z | N | Isotopic mass (Da)[2] [n 2][n 3] |
Half-life [n 4] |
Decay mode [n 5] |
Daughter isotope |
Spin and parity [n 6][n 4] |
Isotopic abundance | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Excitation energy[n 4] | |||||||||||||||||||
| 197Fr | 87 | 110 | 197.01101(6) | 2.3(19) ms | α | 193At | (7/2−) | ||||||||||||
| 198Fr | 87 | 111 | 198.01028(3) | 15(3) ms | α | 194At | 3+# | ||||||||||||
| 199Fr | 87 | 112 | 199.007269(15) | 16(7) ms | α | 195At | 1/2+# | ||||||||||||
| 200Fr | 87 | 113 | 200.00658(3) | 24(10) ms | α | 196At | 3+# | ||||||||||||
| 200mFr | 60(110) keV | 190(120) ms | α | 196At | 10−# | ||||||||||||||
| 201Fr | 87 | 114 | 201.003852(10) | 67(3) ms | α (99%) | 197At | (9/2−) | ||||||||||||
| β+ (1%) | 201Rn | ||||||||||||||||||
| 202Fr | 87 | 115 | 202.003330(6) | 290(30) ms | α (97%) | 198At | (3+) | ||||||||||||
| β+ (3%) | 202Rn | ||||||||||||||||||
| 202mFr | 330(90)# keV | 340(40) ms | α (97%) | 198At | (10−) | ||||||||||||||
| β+ (3%) | 202Rn | ||||||||||||||||||
| 203Fr | 87 | 116 | 203.000941(7) | 0.55(2) s | α (95%) | 199At | (9/2−)# | ||||||||||||
| β+ (5%) | 203Rn | ||||||||||||||||||
| 204Fr | 87 | 117 | 204.000652(26) | 1.7(3) s | α (96%) | 200At | (3+) | ||||||||||||
| β+ (4%) | 204Rn | ||||||||||||||||||
| 204m1Fr | 50(4) keV | 2.6(3) s | α (90%) | 200At | (7+) | ||||||||||||||
| β+ (10%) | 204Rn | ||||||||||||||||||
| 204m2Fr | 326(4) keV | 1.7(6) s | (10−) | ||||||||||||||||
| 205Fr | 87 | 118 | 204.998594(8) | 3.80(3) s | α (99%) | 201At | (9/2−) | ||||||||||||
| β+ (1%) | 205Rn | ||||||||||||||||||
| 206Fr | 87 | 119 | 205.998661(30) | ~16 s | β+ (58%) | 206Rn | (2+, 3+) | ||||||||||||
| α (42%) | 202At | ||||||||||||||||||
| 206m1Fr | 190(40) keV | 15.9(1) s | (7+) | ||||||||||||||||
| 206m2Fr | 730(40) keV | 700(100) ms | (10−) | ||||||||||||||||
| 207Fr | 87 | 120 | 206.996941(19) | 14.8(1) s | α (95%) | 203At | 9/2− | ||||||||||||
| β+ (5%) | 207Rn | ||||||||||||||||||
| 208Fr | 87 | 121 | 207.997139(13) | 59.1(3) s | α (90%) | 204At | 7+ | ||||||||||||
| β+ (10%) | 208Rn | ||||||||||||||||||
| 209Fr | 87 | 122 | 208.995940(12) | 50.0(3) s | α (89%) | 205At | 9/2− | ||||||||||||
| β+ (11%) | 209Rn | ||||||||||||||||||
| 210Fr | 87 | 123 | 209.996411(14) | 3.18(6) min | α (60%) | 206At | 6+ | ||||||||||||
| β+ (40%) | 210Rn | ||||||||||||||||||
| 211Fr | 87 | 124 | 210.995555(13) | 3.10(2) min | α (80%) | 207At | 9/2− | ||||||||||||
| β+ (20%) | 211Rn | ||||||||||||||||||
| 212Fr | 87 | 125 | 211.996225(9) | 20.0(6) min | β+ (57%) | 212Rn | 5+ | ||||||||||||
| α (43%) | 208At | ||||||||||||||||||
| 213Fr | 87 | 126 | 212.996184(5) | 34.14(6) s[3] | α (99.45%) | 209At | 9/2− | ||||||||||||
| β+ (.55%) | 213Rn | ||||||||||||||||||
| 214Fr | 87 | 127 | 213.998971(9) | 5.0(2) ms | α | 210At | (1−) | ||||||||||||
| 214m1Fr | 123(6) keV | 3.35(5) ms | α | 210At | (8−) | ||||||||||||||
| 214m2Fr | 638(6) keV | 103(4) ns | (11+) | ||||||||||||||||
| 214m3Fr | 6477+Y keV | 108(7) ns | (33+) | ||||||||||||||||
| 215Fr | 87 | 128 | 215.000342(8) | 86(5) ns | α | 211At | 9/2− | ||||||||||||
| 216Fr | 87 | 129 | 216.003190(4) | 0.70(2) μs | α | 212At | (1−) | ||||||||||||
| 216mFr | 219(6) keV | 850(30) ns | α[n 7] | 212At | (9−) | ||||||||||||||
| 217Fr | 87 | 130 | 217.004632(7) | 16.8(19) μs | α | 213At | 9/2− | ||||||||||||
| 218Fr | 87 | 131 | 218.007579(5) | 1.0(6) ms | α | 214At | 1− | ||||||||||||
| 218m1Fr | 86(4) keV | 22.0(5) ms | α | 214At | (8−) | ||||||||||||||
| 218m2Fr | 200(150)# keV | high | |||||||||||||||||
| 219Fr | 87 | 132 | 219.009251(7) | 20(2) ms | α | 215At | 9/2− | ||||||||||||
| 220Fr | 87 | 133 | 220.012327(4) | 27.4(3) s | α (99.65%) | 216At | 1+ | ||||||||||||
| β− (.35%) | 220Ra | ||||||||||||||||||
| 221Fr | 87 | 134 | 221.014254(5) | 4.9(2) min | α (99.9%) | 217At | 5/2− | Trace[n 8] | |||||||||||
| β− (.1%) | 221Ra | ||||||||||||||||||
| CD (8.79×10−11%)[n 9] | 207Tl 14C | ||||||||||||||||||
| 222Fr | 87 | 135 | 222.017583(8) | 14.2(3) min | β− | 222Ra | 2− | ||||||||||||
| 223Fr | Actinium K | 87 | 136 | 223.0197342(21) | 22.00(7) min | β− (99.99%) | 223Ra | 3/2(−) | Trace[n 10] | ||||||||||
| α (.006%) | 219At | ||||||||||||||||||
| 224Fr | 87 | 137 | 224.023348(12) | 3.33(10) min | β− | 224Ra | 1− | ||||||||||||
| 225Fr | 87 | 138 | 225.025572(13) | 4.0(2) min | β− | 225Ra | 3/2− | ||||||||||||
| 226Fr | 87 | 139 | 226.029545(7) | 49(1) s | β− | 226Ra | 1− | ||||||||||||
| 227Fr | 87 | 140 | 227.031865(6) | 2.47(3) min | β− | 227Ra | 1/2+ | ||||||||||||
| 228Fr | 87 | 141 | 228.035839(7) | 38(1) s | β− | 228Ra | 2− | ||||||||||||
| 229Fr | 87 | 142 | 229.038291(5) | 50.2(4) s | β− | 229Ra | (1/2+)# | ||||||||||||
| 230Fr | 87 | 143 | 230.042391(7) | 19.1(5) s | β− | 230Ra | |||||||||||||
| 231Fr | 87 | 144 | 231.045175(8) | 17.6(6) s | β− | 231Ra | (1/2+)# | ||||||||||||
| 232Fr | 87 | 145 | 232.049461(15) | 5(1) s | β− | 232Ra | |||||||||||||
| 233Fr | 87 | 146 | 233.052518(21) | 900(100) ms | β− | 233Ra | 1/2+ # | ||||||||||||
| This table header & footer: | |||||||||||||||||||
- ^ mFr – Excited nuclear isomer.
- ^ ( ) – Uncertainty (1σ) is given in concise form in parentheses after the corresponding last digits.
- ^ # – Atomic mass marked #: value and uncertainty derived not from purely experimental data, but at least partly from trends from the Mass Surface (TMS).
- ^ a b c # – Values marked # are not purely derived from experimental data, but at least partly from trends of neighboring nuclides (TNN).
- ^
Modes of decay:
CD: Cluster decay IT: Isomeric transition - ^ ( ) spin value – Indicates spin with weak assignment arguments.
- ^ Theoretically capable of β+ decay to 216Rn[1]
- ^ Intermediate decay product of 237Np
- ^ The nuclide with the lowest atomic number known to undergo cluster decay
- ^ Intermediate decay product of 235U
References
edit- ^ a b Kondev, F. G.; Wang, M.; Huang, W. J.; Naimi, S.; Audi, G. (2021). "The NUBASE2020 evaluation of nuclear properties" (PDF). Chinese Physics C. 45 (3): 030001. doi:10.1088/1674-1137/abddae.
- ^ Wang, Meng; Huang, W.J.; Kondev, F.G.; Audi, G.; Naimi, S. (2021). "The AME 2020 atomic mass evaluation (II). Tables, graphs and references*". Chinese Physics C. 45 (3): 030003. doi:10.1088/1674-1137/abddaf.
- ^ Fisichella, M.; Musumarra, A.; Farinon, F.; Nociforo, C.; Del Zoppo, A.; Figuera, P.; La Cognata, M.; Pellegriti, M. G.; Scuderi, V.; Torresi, D.; Strano, E. (2013-07-24). "Determination of the half-life of 213Fr with high precision". Physical Review C. 88 (1). American Physical Society (APS): 011303. Bibcode:2013PhRvC..88a1303F. doi:10.1103/physrevc.88.011303. ISSN 0556-2813.
- Half-life, spin, and isomer data selected from the following sources.
- Audi, Georges; Bersillon, Olivier; Blachot, Jean; Wapstra, Aaldert Hendrik (2003), "The NUBASE evaluation of nuclear and decay properties", Nuclear Physics A, 729: 3–128, Bibcode:2003NuPhA.729....3A, doi:10.1016/j.nuclphysa.2003.11.001
- National Nuclear Data Center. "NuDat 2.x database". Brookhaven National Laboratory.
- Holden, Norman E. (2004). "11. Table of the Isotopes". In Lide, David R. (ed.). CRC Handbook of Chemistry and Physics (85th ed.). Boca Raton, Florida: CRC Press. ISBN 978-0-8493-0485-9.