Average atomic weight: 140.116(1) u
| Isotope | Fraction | Atomic weight/u |
| 136 | 0.00185(2) | 135.90712921(41) |
| 138 | 0.00251(2) | 137.905991(11) |
| 140 | 0.88450(51) | 139.9054431(23) |
| 142 | 0.11114(51) | 141.9092504(29) |
Atomic weights and isotopic compositions were obtained from NIST Database 144
The Atomic Line List does not contain any data for this element
(Atomic Line List v3.00b5)
