Francium (Fr) has no stable isotopes. A standard atomic mass cannot be given. Its most stable isotope is 223Fr with a half-life of 22 minutes, which is also the only naturally occurring isotope, occurring in trace quantities 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 greater than or equal to 106 (Seaborgium) have most-stable-known isotopes shorter than that of Francium, but those elements have only a relatively small number of isotopes discovered, thus, there is the possibility of a yet-unknown isotope having a longer half-life.
nuclide symbol |
historic name |
Z(p) | N(n) | isotopic mass (u) |
half-life | decay mode(s)[1][n 1] |
daughter isotope(s) |
nuclear spin |
representative isotopic composition (mole fraction) |
range of natural variation (mole fraction) |
---|---|---|---|---|---|---|---|---|---|---|
excitation energy | ||||||||||
199Fr | 87 | 112 | 199.00726(4) | 16(7) ms | 1/2+# | |||||
200Fr | 87 | 113 | 200.00657(8) | 24(10) ms | α | 196At | 3+# | |||
200mFr | 60(110) keV | 650(210) ms | α | 196At | 10-# | |||||
IT (rare) | 200Fr | |||||||||
201Fr | 87 | 114 | 201.00386(8) | 67(3) ms | α (99%) | 197At | (9/2-) | |||
β+ (1%) | 201Rn | |||||||||
202Fr | 87 | 115 | 202.00337(5) | 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 | 203.000925(17) | 0.55(2) s | α (95%) | 199At | (9/2-)# | |||
β+ (5%) | 203Rn | |||||||||
204Fr | 87 | 117 | 204.000653(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 | 205.99867(3) | ~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 | 206.99695(5) | 14.8(1) s | α (95%) | 203At | 9/2- | |||
β+ (5%) | 207Rn | |||||||||
208Fr | 87 | 121 | 207.99714(5) | 59.1(3) s | α (90%) | 204At | 7+ | |||
β+ (10%) | 208Rn | |||||||||
209Fr | 87 | 122 | 208.995954(16) | 50.0(3) s | α (89%) | 205At | 9/2- | |||
β+ (11%) | 209Rn | |||||||||
210Fr | 87 | 123 | 209.996408(24) | 3.18(6) min | α (60%) | 206At | 6+ | |||
β+ (40%) | 210Rn | |||||||||
211Fr | 87 | 124 | 210.995537(23) | 3.10(2) min | α (80%) | 207At | 9/2- | |||
β+ (20%) | 211Rn | |||||||||
212Fr | 87 | 125 | 211.996202(28) | 20.0(6) min | β+ (57%) | 212Rn | 5+ | |||
α (43%) | 208At | |||||||||
213Fr | 87 | 126 | 212.996189(8) | 34.6(3) s | 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 | 215.000341(8) | 86(5) ns | α | 211At | 9/2- | |||
216Fr | 87 | 129 | 216.003198(15) | 0.70(2) µs | α | 212At | (1-) | |||
β+ (2×10−7%) | 216Rn | |||||||||
217Fr | 87 | 130 | 217.004632(7) | 16.8(19) µs | α | 213At | 9/2- | |||
218Fr | 87 | 131 | 218.007578(5) | 1.0(6) ms | α | 214At | 1- | |||
218m1Fr | 86(4) keV | 22.0(5) ms | α | 214At | ||||||
IT (rare) | 218Fr | |||||||||
218m2Fr | 200(150)# keV | high | ||||||||
219Fr | 87 | 132 | 219.009252(8) | 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 | 221.014255(5) | 4.9(2) min | α (99.9%) | 217At | 5/2- | |||
β- (.1%) | 221Ra | |||||||||
CD (8.79×−11%) | 207Tl 14C |
|||||||||
222Fr | 87 | 135 | 222.017552(23) | 14.2(3) min | β- | 222Ra | 2- | |||
223Fr | Actinium K | 87 | 136 | 223.0197359(26) | 22.00(7) min | β- (99.99%) | 223Ra | 3/2(-) | Trace[n 2] | |
α (.006%) | 219At | |||||||||
224Fr | 87 | 137 | 224.02325(5) | 3.33(10) min | β- | 224Ra | 1- | |||
225Fr | 87 | 138 | 225.02557(3) | 4.0(2) min | β- | 225Ra | 3/2- | |||
226Fr | 87 | 139 | 226.02939(11) | 49(1) s | β- | 226Ra | 1- | |||
227Fr | 87 | 140 | 227.03184(11) | 2.47(3) min | β- | 227Ra | 1/2+ | |||
228Fr | 87 | 141 | 228.03573(22)# | 38(1) s | β- | 228Ra | 2- | |||
229Fr | 87 | 142 | 229.03845(4) | 50.2(4) s | β- | 229Ra | (1/2+)# | |||
230Fr | 87 | 143 | 230.04251(48)# | 19.1(5) s | β- | 230Ra | ||||
231Fr | 87 | 144 | 231.04544(50)# | 17.6(6) s | β- | 231Ra | (1/2+)# | |||
232Fr | 87 | 145 | 232.04977(69)# | 5(1) s | β- | 232Ra |
Isotopes of radon | Isotopes of francium | Isotopes of radium |
Index to isotope pages · Table of nuclides |