(this element does not have any stable isotopes)
Atomic weight of the most stable isotope: 222.0175782(25) u
| Isotope | Atomic weight/u | Half-life |
| 199 | 198.998390(68) | 0.59 s 3 |
| 200 | 199.995690(14) | 1.03 s +20-11 |
| 201 | 200.995628(53) | 7.0 s 4 |
| 202 | 201.993264(19) | 9.7 s 1 |
| 203 | 202.993388(25) | 44 s 2 |
| 204 | 203.991430(16) | 74.5 s 14 |
| 205 | 204.991719(54) | 170 s 4 |
| 206 | 205.990214(16) | 5.67 m 17 |
| 207 | 206.9907303(91) | 9.25 m 17 |
| 208 | 207.989635(12) | 24.35 m 14 |
| 209 | 208.990415(22) | 28.8 m 10 |
| 210 | 209.9896891(49) | 2.4 h 1 |
| 211 | 210.9906011(73) | 14.6 h 2 |
| 212 | 211.9907039(34) | 23.9 m 12 |
| 219 | 219.0094804(27) | 3.96 s 1 |
| 220 | 220.0113941(23) | 55.6 s 1 |
| 221 | 221.0155371(63) | 25 m 2 |
| 222 | 222.0175782(25) | 3.8235 d 3 |
| 223 | 223.0218893(84) | 24.3 m 4 |
| 224 | 224.024096(11) | 107 m 3 |
| 225 | 225.028486(12) | 4.66 m 4 |
| 226 | 226.030861(11) | 7.4 m 1 |
| 227 | 227.035304(15) | 20.2 s 4 |
| 228 | 228.037835(19) | 65 s 2 |
| 229 | 229.042257(14) | 12.0 s +12-13 |
Units: y = year, d = day, h = hour, m = minute, s = second, ms = millisecond, µs = microsecond.
Numbers in italics are uncertainties with the same unit as the last digit of the half-life.
Atomic weights were obtained from NIST Database 144
The half-life of radioactive isotopes was obtained from the Nuclear Wallet Cards
The Atomic Line List does not contain any data for this element
(Atomic Line List v3.00b5)
