# Isotopes of francium

Francium ($_{87}$Fr) has no stable isotopes, thus a standard atomic weight cannot be given. Its most stable isotope is $^{223}$Fr with a half-life of 22 minutes, occurring in trace quantities in nature as an intermediate decay product of $^{235}$U.
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

| Nuclide | Historic name | Z | N | Isotopic mass (Da) | Half-life | Decay mode | Daughter isotope | Spin and parity | Isotopic abundance |
| Isotopic abundance |||
| $^{197}$Fr | | 87 | 110 | 197.01101(6) | 2.3(19) ms | α | $^{193}$At | (7/2−) | |
| $^{198}$Fr | | 87 | 111 | 198.01028(3) | 15(3) ms | α | $^{194}$At | 3+# | |
| $^{199}$Fr | | 87 | 112 | 199.007269(15) | 16(7) ms | α | $^{195}$At | 1/2+# | |
| $^{200}$Fr | | 87 | 113 | 200.00658(3) | 24(10) ms | α | $^{196}$At | 3+# | |
| $^{200m}$Fr | | 60(110) keV | 60(110) keV | 60(110) keV | 190(120) ms | α | $^{196}$At | 10−# | |
| $^{201}$Fr | | 87 | 114 | 201.003852(10) | 67(3) ms | α (99%) | $^{197}$At | (9/2−) | |
| $^{201}$Fr | | 87 | 114 | 201.003852(10) | 67(3) ms | β$^+$ (1%) | $^{201}$Rn | (9/2−) | |
| $^{202}$Fr | | 87 | 115 | 202.003330(6) | 290(30) ms | α (97%) | $^{198}$At | (3+) | |
| $^{202}$Fr | | 87 | 115 | 202.003330(6) | 290(30) ms | β$^+$ (3%) | $^{202}$Rn | (3+) | |
| $^{202m}$Fr | | 330(90)# keV | 330(90)# keV | 330(90)# keV | 340(40) ms | α (97%) | $^{198}$At | (10−) | |
| $^{202m}$Fr | | 330(90)# keV | 330(90)# keV | 330(90)# keV | 340(40) ms | β$^+$ (3%) | $^{202}$Rn | (10−) | |
| $^{203}$Fr | | 87 | 116 | 203.000941(7) | 0.55(2) s | α (95%) | $^{199}$At | (9/2−)# | |
| $^{203}$Fr | | 87 | 116 | 203.000941(7) | 0.55(2) s | β$^+$ (5%) | $^{203}$Rn | (9/2−)# | |
| $^{204}$Fr | | 87 | 117 | 204.000652(26) | 1.7(3) s | α (96%) | $^{200}$At | (3+) | |
| $^{204}$Fr | | 87 | 117 | 204.000652(26) | 1.7(3) s | β$^+$ (4%) | $^{204}$Rn | (3+) | |
| $^{204m1}$Fr | | 50(4) keV | 50(4) keV | 50(4) keV | 2.6(3) s | α (90%) | $^{200}$At | (7+) | |
| $^{204m1}$Fr | | 50(4) keV | 50(4) keV | 50(4) keV | 2.6(3) s | β$^+$ (10%) | $^{204}$Rn | (7+) | |
| $^{204m2}$Fr | | 326(4) keV | 326(4) keV | 326(4) keV | 1.7(6) s | | | (10−) | |
| $^{205}$Fr | | 87 | 118 | 204.998594(8) | 3.80(3) s | α (99%) | $^{201}$At | (9/2−) | |
| $^{205}$Fr | | 87 | 118 | 204.998594(8) | 3.80(3) s | β$^+$ (1%) | $^{205}$Rn | (9/2−) | |
| $^{206}$Fr | | 87 | 119 | 205.998661(30) | ~16 s | β$^+$ (58%) | $^{206}$Rn | (2+, 3+) | |
| $^{206}$Fr | | 87 | 119 | 205.998661(30) | ~16 s | α (42%) | $^{202}$At | (2+, 3+) | |
| $^{206m1}$Fr | | 190(40) keV | 190(40) keV | 190(40) keV | 15.9(1) s | | | (7+) | |
| $^{206m2}$Fr | | 730(40) keV | 730(40) keV | 730(40) keV | 700(100) ms | | | (10−) | |
| $^{207}$Fr | | 87 | 120 | 206.996941(19) | 14.8(1) s | α (95%) | $^{203}$At | 9/2− | |
| $^{207}$Fr | | 87 | 120 | 206.996941(19) | 14.8(1) s | β$^+$ (5%) | $^{207}$Rn | 9/2− | |
| $^{208}$Fr | | 87 | 121 | 207.997139(13) | 59.1(3) s | α (90%) | $^{204}$At | 7+ | |
| $^{208}$Fr | | 87 | 121 | 207.997139(13) | 59.1(3) s | β$^+$ (10%) | $^{208}$Rn | 7+ | |
| $^{209}$Fr | | 87 | 122 | 208.995940(12) | 50.0(3) s | α (89%) | $^{205}$At | 9/2− | |
| $^{209}$Fr | | 87 | 122 | 208.995940(12) | 50.0(3) s | β$^+$ (11%) | $^{209}$Rn | 9/2− | |
| $^{210}$Fr | | 87 | 123 | 209.996411(14) | 3.18(6) min | α (60%) | $^{206}$At | 6+ | |
| $^{210}$Fr | | 87 | 123 | 209.996411(14) | 3.18(6) min | β$^+$ (40%) | $^{210}$Rn | 6+ | |
| $^{211}$Fr | | 87 | 124 | 210.995555(13) | 3.10(2) min | α (80%) | $^{207}$At | 9/2− | |
| $^{211}$Fr | | 87 | 124 | 210.995555(13) | 3.10(2) min | β$^+$ (20%) | $^{211}$Rn | 9/2− | |
| $^{212}$Fr | | 87 | 125 | 211.996225(9) | 20.0(6) min | β$^+$ (57%) | $^{212}$Rn | 5+ | |
| $^{212}$Fr | | 87 | 125 | 211.996225(9) | 20.0(6) min | α (43%) | $^{208}$At | 5+ | |
| $^{213}$Fr | | 87 | 126 | 212.996184(5) | 34.14(6) s | α (99.45%) | $^{209}$At | 9/2− | |
| $^{213}$Fr | | 87 | 126 | 212.996184(5) | 34.14(6) s | β$^+$ (.55%) | $^{213}$Rn | 9/2− | |
| $^{214}$Fr | | 87 | 127 | 213.998971(9) | 5.0(2) ms | α | $^{210}$At | (1−) | |
| $^{214m1}$Fr | | 123(6) keV | 123(6) keV | 123(6) keV | 3.35(5) ms | α | $^{210}$At | (8−) | |
| $^{214m2}$Fr | | 638(6) keV | 638(6) keV | 638(6) keV | 103(4) ns | | | (11+) | |
| $^{214m3}$Fr | | 6477+Y keV | 6477+Y keV | 6477+Y keV | 108(7) ns | | | (33+) | |
| $^{215}$Fr | | 87 | 128 | 215.000342(8) | 86(5) ns | α | $^{211}$At | 9/2− | |
| $^{216}$Fr | | 87 | 129 | 216.003190(4) | 0.70(2) μs | α | $^{212}$At | (1−) | |
| $^{216m}$Fr | | 219(6) keV | 219(6) keV | 219(6) keV | 850(30) ns | α | $^{212}$At | (9−) | |
| $^{217}$Fr | | 87 | 130 | 217.004632(7) | 16.8(19) μs | α | $^{213}$At | 9/2− | |
| $^{218}$Fr | | 87 | 131 | 218.007579(5) | 1.0(6) ms | α | $^{214}$At | 1− | |
| $^{218m1}$Fr | | 86(4) keV | 86(4) keV | 86(4) keV | 22.0(5) ms | α | $^{214}$At | (8−) | |
| $^{218m2}$Fr | | 200(150)# keV | 200(150)# keV | 200(150)# keV | | | | high | |
| $^{219}$Fr | | 87 | 132 | 219.009251(7) | 20(2) ms | α | $^{215}$At | 9/2− | |
| $^{220}$Fr | | 87 | 133 | 220.012327(4) | 27.4(3) s | α (99.65%) | $^{216}$At | 1+ | |
| $^{220}$Fr | | 87 | 133 | 220.012327(4) | 27.4(3) s | β$^−$ (.35%) | $^{220}$Ra | 1+ | |
| $^{221}$Fr | | 87 | 134 | 221.014254(5) | 4.801(5) min | α (99.9%) | $^{217}$At | 5/2− | Trace |
| $^{221}$Fr | | 87 | 134 | 221.014254(5) | 4.801(5) min | β$^−$ (.1%) | $^{221}$Ra | 5/2− | Trace |
| $^{221}$Fr | | 87 | 134 | 221.014254(5) | 4.801(5) min | CD (8.79×10$^{−11}$%) | $^{207}$Tl $^{14}$C | 5/2− | Trace |
| $^{222}$Fr | | 87 | 135 | 222.017583(8) | 14.2(3) min | β$^−$ | $^{222}$Ra | 2− | |
| $^{223}$Fr | Actinium K | 87 | 136 | 223.0197342(21) | 22.00(7) min | β$^−$ (99.99%) | $^{223}$Ra | 3/2(−) | Trace |
| $^{223}$Fr | Actinium K | 87 | 136 | 223.0197342(21) | 22.00(7) min | α (.006%) | $^{219}$At | 3/2(−) | Trace |
| $^{224}$Fr | | 87 | 137 | 224.023348(12) | 3.33(10) min | β$^−$ | $^{224}$Ra | 1− | |
| $^{225}$Fr | | 87 | 138 | 225.025572(13) | 4.0(2) min | β$^−$ | $^{225}$Ra | 3/2− | |
| $^{226}$Fr | | 87 | 139 | 226.029545(7) | 49(1) s | β$^−$ | $^{226}$Ra | 1− | |
| $^{227}$Fr | | 87 | 140 | 227.031865(6) | 2.47(3) min | β$^−$ | $^{227}$Ra | 1/2+ | |
| $^{228}$Fr | | 87 | 141 | 228.035839(7) | 38(1) s | β$^−$ | $^{228}$Ra | 2− | |
| $^{229}$Fr | | 87 | 142 | 229.038291(5) | 50.2(4) s | β$^−$ | $^{229}$Ra | (1/2+)# | |
| $^{230}$Fr | | 87 | 143 | 230.042391(7) | 19.1(5) s | β$^−$ | $^{230}$Ra | | |
| $^{231}$Fr | | 87 | 144 | 231.045175(8) | 17.6(6) s | β$^−$ | $^{231}$Ra | (1/2+)# | |
| $^{232}$Fr | | 87 | 145 | 232.049461(15) | 5(1) s | β$^−$ | $^{232}$Ra | | |
| $^{233}$Fr | | 87 | 146 | 233.052518(21) | 900(100) ms | β$^−$ | $^{233}$Ra | 1/2+ # | |
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* ↑ $^m$Fr – 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).
* 1 2 3 # – 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 $^{216}$Rn
* ↑ Intermediate decay product of $^{237}$Np
* ↑ The nuclide with the lowest atomic number known to undergo cluster decay
* ↑ Intermediate decay product of $^{235}$U