URANIUM Y (ACTINIUM) SERIES
| Element | Atomic Weight | T (average time-period—half transformed) | Rays (given out in each decomposition) |
| Uranium Y | 234 | (+) 24.6 hrs. | Beta |
| (branching from Uranium II) | (2.2 days?) | ||
| Protoactinium | 230 | About 104 yrs. (?) | Alpha |
| Actinium | 226 | 20 yrs. | Beta |
| Radio-actinium | 226 | 19 days | Alpha |
| Actinium X | 222 | (+) 11.2 days | Alpha |
| Actinium (Emanation) | 218 | 3.92 sec. | Alpha |
| Actinium A | 214 | .002 sec. | Alpha |
| Actinium B | 210 | 36 min. (?) | Beta, Gamma |
| Actinium C | 210 | 2.16 min. (?) | Alpha |
| Actinium D | 206 | 4.76 min. | Beta, Gamma |
| Actinium E (End-product actinium-lead) | 206 | ............... | ............... |