Isotopes of francium

Francium (₈₇Fr) has no stable isotopes, so 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, though astatine is the rarest in nature due to its naturally occurring isotopes having even shorter half-lives and even smaller branching ratios.

The elements with atomic number of 106 (seaborgium) or greater have their longest known half-life of any isotope shorter than that of francium, but as those elements have only isotopes on the proton-rich side of beta stability discovered, there is a strong possibility that undiscovered isotopes of these elements will have longer half-lives that could exceed that of francium-223.

List of isotopes

|-id=Francium-197 | ¹⁹⁷Fr | | style="text-align:right" | 87 | style="text-align:right" | 110 | 197.01101(6) | 2.3(19)&nbsp;ms | α | ¹⁹³At | (7/2−) | |-id=Francium-198 | ¹⁹⁸Fr | | style="text-align:right" | 87 | style="text-align:right" | 111 | 198.01028(3) | 15(3)&nbsp;ms | α | ¹⁹⁴At | 3+# | |-id=Francium-198m | style="text-indent:1em" | ^198mFr | | colspan="3" style="text-indent:2em" | 0(50)&nbsp;keV | 1.1(7)&nbsp;ms | α | ¹⁹⁴At | (10−) | |-id=Francium-199 | ¹⁹⁹Fr | | style="text-align:right" | 87 | style="text-align:right" | 112 | 199.007269(15) | 6.6(22)&nbsp;ms | α | ¹⁹⁵At | 1/2+# | |-id=Francium-199m1 | style="text-indent:1em" | ^199m1Fr | | colspan="3" style="text-indent:2em" | 45(13)&nbsp;keV | 6.5(9)&nbsp;ms | α | ¹⁹⁵At | 7/2−# | |-id=Francium-199m2 | style="text-indent:1em" | ^199m2Fr | | colspan="3" style="text-indent:2em" | 250(50)#&nbsp;keV | 2.2(12)&nbsp;ms | α | ¹⁹⁵At | 13/2+# | |-id=Francium-200 | ²⁰⁰Fr | | style="text-align:right" | 87 | style="text-align:right" | 113 | 200.00658(3) | 47.5(28)&nbsp;ms | α | ¹⁹⁶At | (3+) | |-id=Francium-200m1 | style="text-indent:1em" | ^200m1Fr | | colspan="3" style="text-indent:2em" | 50(60)&nbsp;keV | 190(120)&nbsp;ms | α | ¹⁹⁶At | 10−# | |-id=Francium-200m2 | style="text-indent:1em" | ^200m2Fr | | colspan="3" style="text-indent:2em" | 150(50)#&nbsp;keV | 790(360)&nbsp;ns | | | | |-id=Francium-201 | ²⁰¹Fr | | style="text-align:right" | 87 | style="text-align:right" | 114 | 201.003852(10) | 62.8(19)&nbsp;ms | α | ¹⁹⁷At | 9/2− | |-id=Francium-201m1 | style="text-indent:1em" | ^201m1Fr | | colspan="3" style="text-indent:2em" | 129(10)&nbsp;keV | 24(6)&nbsp;ms | α | ¹⁹⁷At | 1/2+ | |-id=Francium-201m2 | style="text-indent:1em" | ^201m2Fr | | colspan="3" style="text-indent:2em" | 289.5(4)&nbsp;keV | 720(40)&nbsp;ns | IT | ²⁰¹Fr | 13/2+ | |-id=Francium-202 | ²⁰²Fr | | style="text-align:right" | 87 | style="text-align:right" | 115 | 202.003330(6) | 372(12)&nbsp;ms | α | ¹⁹⁸At | 3+ | |-id=Francium-202m | rowspan=2 style="text-indent:1em" | ^202mFr | rowspan=2| | rowspan=2 colspan="3" style="text-indent:2em" | 257(6)&nbsp;keV | rowspan=2|286(13)&nbsp;ms | α | ¹⁹⁸At | rowspan=2|10− | rowspan=2| |- | IT (?%) | ²⁰²Fr |-id=Francium-203 | ²⁰³Fr | | style="text-align:right" | 87 | style="text-align:right" | 116 | 203.000941(7) | 550(10)&nbsp;ms | α | ¹⁹⁹At | 9/2− | |-id=Francium-203m1 | rowspan=2 style="text-indent:1em" | ^203m1Fr | rowspan=2| | rowspan=2 colspan="3" style="text-indent:2em" | 361(6)&nbsp;keV | rowspan=2|43(4)&nbsp;ms | IT (80%) | ²⁰³Fr | rowspan=2|1/2+ | rowspan=2| |- | α (20%) | ¹⁹⁹At |-id=Francium-203m2 | style="text-indent:1em" | ^203m2Fr | | colspan="3" style="text-indent:2em" | 426.0(10)&nbsp;keV | 370(50)&nbsp;ns | IT | ²⁰³Fr | 13/2+ | |-id=Francium-204 | rowspan=2|²⁰⁴Fr | rowspan=2| | rowspan=2 style="text-align:right" | 87 | rowspan=2 style="text-align:right" | 117 | rowspan=2|204.000652(26) | rowspan=2|1.75(26)&nbsp;s | α (96%) | ²⁰⁰At | rowspan=2|3+ | rowspan=2| |- | β⁺ (4%) | ²⁰⁴Rn |-id=Francium-204m1 | rowspan=2 style="text-indent:1em" | ^204m1Fr | rowspan=2| | rowspan=2 colspan="3" style="text-indent:2em" | 50(4)&nbsp;keV | rowspan=2|2.41(19)&nbsp;s | α (90%) | ²⁰⁰At | rowspan=2|7+ | rowspan=2| |- | β⁺ (10%) | ²⁰⁴Rn |-id=Francium-204m2 | rowspan=2 style="text-indent:1em" | ^204m2Fr | rowspan=2| | rowspan=2 colspan="3" style="text-indent:2em" | 326(4)&nbsp;keV | rowspan=2|1.65(15)&nbsp;s | α (53%) | ²⁰⁰At | rowspan=2|10− | rowspan=2| |- | IT (47%) | ²⁰⁴Fr |-id=Francium-205 | rowspan=2|²⁰⁵Fr | rowspan=2| | rowspan=2 style="text-align:right" | 87 | rowspan=2 style="text-align:right" | 118 | rowspan=2|204.998594(8) | rowspan=2|3.90(7)&nbsp;s | α (98.5%) | ²⁰¹At | rowspan=2|9/2− | rowspan=2| |- | β⁺ (1.5%) | ²⁰⁵Rn |-id=Francium-205m1 | style="text-indent:1em" | ^205m1Fr | | colspan="3" style="text-indent:2em" | 544.0(10)&nbsp;keV | 80(20)&nbsp;ns | IT | ²⁰⁵Fr | 13/2+ | |-id=Francium-205m2 | style="text-indent:1em" | ^205m2Fr | | colspan="3" style="text-indent:2em" | 609(6)&nbsp;keV | 1.15(4)&nbsp;ms | IT | ²⁰³Fr | (1/2+) | |-id=Francium-206 | rowspan=2|²⁰⁶Fr | rowspan=2| | rowspan=2 style="text-align:right" | 87 | rowspan=2 style="text-align:right" | 119 | rowspan=2|205.998661(30) | rowspan=2|~16&nbsp;s | α (88.4%) | ²⁰²At | rowspan=2|3+ | rowspan=2| |- | β⁺ (11.6%) | ²⁰⁶Rn |-id=Francium-206m1 | rowspan=3 style="text-indent:1em" | ^206m1Fr | rowspan=3| | rowspan=3 colspan="3" style="text-indent:2em" | 200(40)&nbsp;keV | rowspan=3|~16&nbsp;s | α (84.7%) | ²⁰²At | rowspan=3|7+ | rowspan=3| |- | β⁺ (?%) | ²⁰⁶Rn |- | IT (?%) | ²⁰⁶Fr |-id=Francium-206m2 | rowspan=2 style="text-indent:1em" | ^206m2Fr | rowspan=2| | rowspan=2 colspan="3" style="text-indent:2em" | 730(40)&nbsp;keV | rowspan=2|700(100)&nbsp;ms | IT (87%) | ²⁰⁶Fr | rowspan=2|10− | rowspan=2| |- | α (13%) | ²⁰²At |-id=Francium-207 | rowspan=2|²⁰⁷Fr | rowspan=2| | rowspan=2 style="text-align:right" | 87 | rowspan=2 style="text-align:right" | 120 | rowspan=2|206.996941(19) | rowspan=2|14.8(1)&nbsp;s | α (95%) | ²⁰³At | rowspan=2|9/2− | rowspan=2| |- | β⁺ (5%) | ²⁰⁷Rn |-id=Francium-208 | rowspan=2|²⁰⁸Fr | rowspan=2| | rowspan=2 style="text-align:right" | 87 | rowspan=2 style="text-align:right" | 121 | rowspan=2|207.997139(13) | rowspan=2|59.1(3)&nbsp;s | α (89%) | ²⁰⁴At | rowspan=2|7+ | rowspan=2| |- | β⁺ (11%) | ²⁰⁸Rn |-id=Francium-208m | style="text-indent:1em" | ^208mFr | | colspan="3" style="text-indent:2em" | 826.3(5)&nbsp;keV | 432(11)&nbsp;ns | IT | ²⁰⁸Fr | 10− | |-id=Francium-209 | rowspan=2|²⁰⁹Fr | rowspan=2| | rowspan=2 style="text-align:right" | 87 | rowspan=2 style="text-align:right" | 122 | rowspan=2|208.995940(12) | rowspan=2|50.5(7)&nbsp;s | α (89%) | ²⁰⁵At | rowspan=2|9/2− | rowspan=2| |- | β⁺ (11%) | ²⁰⁹Rn |-id=Francium-209m | style="text-indent:1em" | ^209mFr | | colspan="3" style="text-indent:2em" | 4659.8(7)&nbsp;keV | 420(18)&nbsp;ns | IT | ²⁰⁹Fr | 45/2− | |-id=Francium-210 | rowspan=2|²¹⁰Fr | rowspan=2| | rowspan=2 style="text-align:right" | 87 | rowspan=2 style="text-align:right" | 123 | rowspan=2|209.996411(14) | rowspan=2|3.18(6)&nbsp;min | α (71%) | ²⁰⁶At | rowspan=2|6+ | rowspan=2| |- | β⁺ (29%) | ²¹⁰Rn |-id=Francium-210m | style="text-indent:1em" | ^210mFr | | colspan="3" style="text-indent:2em" | 4417.2(10)&nbsp;keV | 475(6)&nbsp;ns | IT | ²¹⁰Fr | (23)+ | |-id=Francium-211 | rowspan=2|²¹¹Fr | rowspan=2| | rowspan=2 style="text-align:right" | 87 | rowspan=2 style="text-align:right" | 124 | rowspan=2|210.995555(13) | rowspan=2|3.10(2)&nbsp;min | α (87%) | ²⁰⁷At | rowspan=2|9/2− | rowspan=2| |- | β⁺ (13%) | ²¹¹Rn |-id=Francium-211m1 | style="text-indent:1em" | ^211m1Fr | | colspan="3" style="text-indent:2em" | 2423.16(24)&nbsp;keV | 146(14)&nbsp;ns | IT | ²¹¹Fr | 29/2+ | |-id=Francium-211m2 | style="text-indent:1em" | ^211m2Fr | | colspan="3" style="text-indent:2em" | 4657.3(4)&nbsp;keV | 124.5(12)&nbsp;ns | IT | ²¹¹Fr | 45/2− | |-id=Francium-212 | rowspan=2|²¹²Fr | rowspan=2| | rowspan=2 style="text-align:right" | 87 | rowspan=2 style="text-align:right" | 125 | rowspan=2|211.996225(9) | rowspan=2|20.0(6)&nbsp;min | β⁺ (57%) | ²¹²Rn | rowspan=2|5+ | rowspan=2| |- | α (43%) | ²⁰⁸At |-id=Francium-212m1 | style="text-indent:1em" | ^212m1Fr | | colspan="3" style="text-indent:2em" | 1551.4(3)&nbsp;keV | 31.9(7)&nbsp;μs | IT | ²¹²Fr | 11+ | |-id=Francium-212m2 | style="text-indent:1em" | ^212m2Fr | | colspan="3" style="text-indent:2em" | 2492.2(4)&nbsp;keV | 604(28)&nbsp;ns | IT | ²¹²Fr | 15− | |-id=Francium-212m3 | style="text-indent:1em" | ^212m3Fr | | colspan="3" style="text-indent:2em" | 5854.7(6)&nbsp;keV | 312(21)&nbsp;ns | IT | ²¹²Fr | 27− | |-id=Francium-212m4 | style="text-indent:1em" | ^212m4Fr | | colspan="3" style="text-indent:2em" | 8533.4(11)&nbsp;keV | 23.6(21)&nbsp;μs | IT | ²¹²Fr | 34+# | |-id=Francium-213 | rowspan=2|²¹³Fr | rowspan=2| | rowspan=2 style="text-align:right" | 87 | rowspan=2 style="text-align:right" | 126 | rowspan=2|212.996184(5) | rowspan=2|34.14(6)&nbsp;s | α (99.44%) | ²⁰⁹At | rowspan=2|9/2− | rowspan=2| |- | β⁺ (0.56%) | ²¹³Rn |-id=Francium-213m1 | style="text-indent:1em" | ^213m1Fr | | colspan="3" style="text-indent:2em" | 1590.41(18)&nbsp;keV | 505(14)&nbsp;ns | IT | ²¹³Fr | 21/2− | |-id=Francium-213m2 | style="text-indent:1em" | ^213m2Fr | | colspan="3" style="text-indent:2em" | 2537.62(23)&nbsp;keV | 238(6)&nbsp;ns | IT | ²¹³Fr | 29/2+ | |-id=Francium-213m3 | style="text-indent:1em" | ^213m3Fr | | colspan="3" style="text-indent:2em" | 8094.8(7)&nbsp;keV | 3.1(2)&nbsp;μs | IT | ²¹³Fr | (65/2−) | |-id=Francium-214 | ²¹⁴Fr | | style="text-align:right" | 87 | style="text-align:right" | 127 | 213.998971(9) | 5.51(13)&nbsp;ms | α | ²¹⁰At | (1−) | |-id=Francium-214m1 | style="text-indent:1em" | ^214m1Fr | | colspan="3" style="text-indent:2em" | 121(5)&nbsp;keV | 3.35(5)&nbsp;ms | α | ²¹⁰At | (8−) | |-id=Francium-214m2 | style="text-indent:1em" | ^214m2Fr | | colspan="3" style="text-indent:2em" | 638(5)&nbsp;keV | 103(4)&nbsp;ns | IT | ²¹⁴Fr | (11+) | |-id=Francium-214m3 | style="text-indent:1em" | ^214m3Fr | | colspan="3" style="text-indent:2em" | 6577(100)#&nbsp;keV | 108(7)&nbsp;ns | IT | ²¹⁴Fr | (33+) | |-id=Francium-215 | ²¹⁵Fr | | style="text-align:right" | 87 | style="text-align:right" | 128 | 215.000342(8) | 90(4)&nbsp;ns | α | ²¹¹At | 9/2− | |-id=Francium-216 |²¹⁶Fr | | style="text-align:right" | 87 | style="text-align:right" | 129 | 216.003190(4) | 700(20)&nbsp;ns | α | ²¹²At | (1−) | |-id=Francium-216m | style="text-indent:1em" | ^216mFr | | colspan="3" style="text-indent:2em" | 219(6)&nbsp;keV | 850(30)&nbsp;ns | α | ^212m1At | (9−) | |-id=Francium-217 | ²¹⁷Fr | | style="text-align:right" | 87 | style="text-align:right" | 130 | 217.004632(7) | 22(5)&nbsp;μs | α | ²¹³At | 9/2− | |-id=Francium-218 | ²¹⁸Fr | | style="text-align:right" | 87 | style="text-align:right" | 131 | 218.007579(5) | 1.4(5)&nbsp;ms | α | ²¹⁴At | 1− | |-id=Francium-218m |style="text-indent:1em" | ^218mFr | | colspan="3" style="text-indent:2em" | 87(4)&nbsp;keV | 21.9(5)&nbsp;ms | α | ²¹⁴At | (8−) | |-id=Francium-219 | ²¹⁹Fr | | style="text-align:right" | 87 | style="text-align:right" | 132 | 219.009251(7) | 22.5(17)&nbsp;ms | α | ²¹⁵At | 9/2− | |-id=Francium-220 | rowspan=2|²²⁰Fr | rowspan=2| | rowspan=2 style="text-align:right" | 87 | rowspan=2 style="text-align:right" | 133 | rowspan=2|220.012327(4) | rowspan=2|27.4(3)&nbsp;s | α (99.65%) | ²¹⁶At | rowspan=2|1+ | rowspan=2| |- | β^− (0.35%) | ²²⁰Ra |-id=Francium-221 | rowspan=3|²²¹Fr | rowspan=3| | rowspan=3 style="text-align:right" | 87 | rowspan=3 style="text-align:right" | 134 | rowspan=3|221.014254(5) | rowspan=3|4.801(5)&nbsp;min | α | ²¹⁷At | rowspan=3|5/2− | rowspan=3|Trace |- | β^− (0.0048%) | ²²¹Ra |- | CD (8.8×10^{−11}%) | ²⁰⁷Tl<br>¹⁴C |-id=Francium-222 | ²²²Fr | | style="text-align:right" | 87 | style="text-align:right" | 135 | 222.017583(8) | 14.2(3)&nbsp;min | β^− | ²²²Ra | 2− | |-id=Francium-223 | rowspan=2|²²³Fr | rowspan=2|Actinium K | rowspan=2 style="text-align:right" | 87 | rowspan=2 style="text-align:right" | 136 | rowspan=2|223.0197342(21) | rowspan=2|22.00(7)&nbsp;min | β^− | ²²³Ra | rowspan=2|3/2− | rowspan=2|Trace |- | α (0.006%) | ²¹⁹At |-id=Francium-224 | ²²⁴Fr | | style="text-align:right" | 87 | style="text-align:right" | 137 | 224.023348(12) | 3.33(10)&nbsp;min | β^− | ²²⁴Ra | 1− | |-id=Francium-225 | ²²⁵Fr | | style="text-align:right" | 87 | style="text-align:right" | 138 | 225.025572(13) | 3.95(14)&nbsp;min | β^− | ²²⁵Ra | 3/2− | |-id=Francium-226 | ²²⁶Fr | | style="text-align:right" | 87 | style="text-align:right" | 139 | 226.029545(7) | 48.5(7)&nbsp;s | β^− | ²²⁶Ra | 1− | |-id=Francium-227 | ²²⁷Fr | | style="text-align:right" | 87 | style="text-align:right" | 140 | 227.031865(6) | 2.47(3)&nbsp;min | β^− | ²²⁷Ra | 1/2+ | |-id=Francium-228 | ²²⁸Fr | | style="text-align:right" | 87 | style="text-align:right" | 141 | 228.035839(7) | 38(1)&nbsp;s | β^− | ²²⁸Ra | 2− | |-id=Francium-228m |style="text-indent:1em" | ^228mFr | | colspan="3" style="text-indent:2em" | 1004(30)&nbsp;keV | 180(110)&nbsp;s | | | | |-id=Francium-229 | ²²⁹Fr | | style="text-align:right" | 87 | style="text-align:right" | 142 | 229.038291(5) | 50.2(4)&nbsp;s | β^− | ²²⁹Ra | (1/2+) | |-id=Francium-230 | ²³⁰Fr | | style="text-align:right" | 87 | style="text-align:right" | 143 | 230.042391(7) | 19.1(5)&nbsp;s | β^− | ²³⁰Ra | 2+# | |-id=Francium-231 | ²³¹Fr | | style="text-align:right" | 87 | style="text-align:right" | 144 | 231.045175(8) | 17.6(6)&nbsp;s | β^− | ²³¹Ra | (1/2+) | |-id=Francium-232 | ²³²Fr | | style="text-align:right" | 87 | style="text-align:right" | 145 | 232.049461(15) | 5.5(6)&nbsp;s | β^− | ²³²Ra | (5) | |-id=Francium-233 | ²³³Fr | | style="text-align:right" | 87 | style="text-align:right" | 146 | 233.052518(21) | 900(100)&nbsp;ms | β^− | ²³³Ra | 1/2+# |

References

• Half-life, spin, and isomer data selected from the following sources.