钫没有稳定的同位素，因此无法得到其标准原子量，但钫存在有两个天然放射性同位素。目前已知的有35种钫的同位素，原子量从199到233，其中最稳定的同位素是钫-223（223
Fr
），半衰期为22分钟，由于是铀-235（235
U
）的衰变产物，因此在地壳中微量存在，而另一个自然同位素是221
Fr
，半衰期较短，只有4.9分钟，目前已知稳定性最差的钫同位素是215
Fr
，半衰期为86纳秒。
Quick Facts 同位素, 衰变 ...
主要的钫同位素
| 同位素
|
衰变
|
|
|
丰度
|
半衰期 (t1/2)
|
方式
|
能量
（MeV）
|
产物
|
| 210Fr
|
人造
|
3.18 分钟
|
α
|
6.671
|
206At
|
| β+
|
5.239
|
210Rn
|
| 211Fr
|
人造
|
3.10 分钟
|
α
|
6.662
|
207At
|
| β+
|
3.593
|
211Rn
|
| 212Fr
|
人造
|
20.0 分钟
|
β+
|
5.143
|
212Rn
|
| α
|
5.507
|
208At
|
| 221Fr
|
痕量
|
4.801 分钟
|
α
|
6.458
|
217At
|
| β−
|
0.313
|
221Ra
|
| 222Fr
|
人造
|
14.2 分钟
|
β−
|
2.058
|
222Ra
|
| 223Fr
|
痕量
|
22.00 分钟
|
β−
|
1.149
|
223Ra
|
| α
|
5.561
|
219At
| |
|
|
|
Close
钫在前105个元素之中最不稳定。106号元素𬭳和之后的元素虽然比钫更不稳定，但因为目前发现的同位素数量不多，所以以后可能会发现更长寿的同位素。
More information 符号, 历史 名称 ...
| 符号
|
历史
名称
|
Z
|
N
|
同位素质量（u）
[n 1][n 2]
|
半衰期
[n 2]
|
衰变
方式[1]
|
衰变
产物
|
原子核
自旋[n 1]
|
相对丰度
（摩尔分率）
|
| 激发能量[n 1][n 2]
|
| 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 （不常见）
|
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 （不常见）
|
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−
|
Trace[n 3]
|
| β− (.1%)
|
221Ra
|
| CD (8.79×10−11%)
|
207Tl
14
C
|
| 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 4]
|
| 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
|
|
|
| 233Fr
|
|
87
|
146
|
233.052518(21)
|
900(100) ms
|
β−
|
233Ra
|
1/2+ #
|
|
Close
画上#号的数据代表没有经过实验的证明，仅为理论推测。
Intermediate decay product of 237Np
Intermediate decay product of 235U
- Isotope masses from Ame2003 Atomic Mass Evaluation by G. Audi, A.H. Wapstra, C. Thibault, J. Blachot and O. Bersillon in Nuclear Physics A729 (2003).
- Half-life, spin, and isomer data selected from these sources. Editing notes on this article's talk page.
- Audi, Bersillon, Blachot, Wapstra. The Nubase2003 evaluation of nuclear and decay properties （页面存档备份，存于互联网档案馆）, Nuc. Phys. A 729, pp. 3-128 (2003).
- National Nuclear Data Center, Brookhaven National Laboratory. Information extracted from the NuDat 2.1 database （页面存档备份，存于互联网档案馆） (retrieved Sept. 2005).
- David R. Lide (ed.), Norman E. Holden in CRC Handbook of Chemistry and Physics, 85th Edition, online version. CRC Press. Boca Raton, Florida (2005). Section 11, Table of the Isotopes.
