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.
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
| Nuclide1 | Historicname | Z | N | Isotopic mass (Da)234 | Half-life5 | Decaymode6 | Daughterisotope | Spin andparity78 | Isotopicabundance | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Excitation energy9 | |||||||||||||||||||
| 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) s10 | 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 | α11 | 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) | 4.801(5) min | α (99.9%) | 217At | 5/2− | Trace12 | |||||||||||
| β− (.1%) | 221Ra | ||||||||||||||||||
| CD (8.79×10−11%)13 | 207Tl14C | ||||||||||||||||||
| 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(−) | Trace14 | ||||||||||
| 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:
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- 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.
References
mFr – Excited nuclear isomer. /wiki/Nuclear_isomer ↩
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. /wiki/Doi_(identifier) ↩
( ) – 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). ↩
# – Values marked # are not purely derived from experimental data, but at least partly from trends of neighboring nuclides (TNN). ↩
Modes of decay: CD:Cluster decayIT:Isomeric transition /wiki/Cluster_decay ↩
( ) spin value – Indicates spin with weak assignment arguments. ↩
# – Values marked # are not purely derived from experimental data, but at least partly from trends of neighboring nuclides (TNN). ↩
# – Values marked # are not purely derived from experimental data, but at least partly from trends of neighboring nuclides (TNN). ↩
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. /wiki/Bibcode_(identifier) ↩
Theoretically capable of β+ decay to 216Rn[1] ↩
Intermediate decay product of 237Np /wiki/Neptunium-237 ↩
The nuclide with the lowest atomic number known to undergo cluster decay /wiki/Atomic_number ↩
Intermediate decay product of 235U /wiki/Decay_product ↩