URANIUM I SERIES
| Element | Atomic Weight | T (average time-period—half transformed) | Rays (given out in each decomposition) |
| Uranium I | 238 | 4.5 × 109 yrs. | Alpha |
| Uranium X1 | 234 | 23.8 days | Beta, Gamma |
| Uranium X2 | 234 | 1.15 min. | Beta, Gamma |
| Uranium II | 234 | About 2 × 106 yrs. | Alpha |
| Ionium | 230 | About 9 × 104 yrs. | Alpha |
| Radium | 226 | (+) 1700 yrs. | Alpha |
| Niton (Emanation) | 222 | 3.85 days | Alpha |
| Radium A | 218 | 3.05 min. (?) | Alpha |
| Radium B | 214 | 26.8 min. (?) | Beta, Gamma |
| Radium C | 214 | 19.5 min. (?) | Alpha, Beta, Gamma |
| Radium C′ | 214 | 10-6 sec. (?) | Alpha |
| Radium D | 210 | (+) 16 yrs. | Beta, Gamma |
| Radium E | 210 | (+) 4.85 days | Beta, Gamma |
| Radium F (Polonium) | 210 | (+) 136.5 days | Alpha |
| Radium G (End-product uranium-lead) | 206 | ............... | ............... |