There are three series by which naturally radioactive nuclei decay to stable ones: The Uranium Series, the Thorium Series, and the Actinium Series. Man-made radioactive nuclei decay similarly, with bismuth as the end product, via the Neptunium Series. These can be illustrated in tabular form and diagrammatically. The Actinium Series (Uranium-235 Series), for example, proceeds like this:
| THE URANIUM-235 SERIES | ||||
|---|---|---|---|---|
| Element | Symbol | Radiation Emitted | Half-life | |
| Uranium | ²³⁵U | α | 7.13 × 10⁸ years | |
| Thorium | ²³¹Th | β | 25.6 hours | |
| Protactinium | ²³¹Pa | α | 3.25 × 10⁴ years | |
| Actinium[16] | ²²⁷Ac | β (98.8%) and α (1.2%) | 21.2 years | |
| Thorium | ²²⁷Th | α | 18.17 days | |
| Francium | ²²³Fr | β | 22 minutes | |
| Radium | ²²³Ra | α | 11.7 days | |
| Radon | ²¹⁹Rn | α | 4.0 seconds | |
| Polonium[16] | ²¹⁵Po | α (~100%) and β (~5 × 10⁻⁴%) | 1.83 × 10⁻³ second | |
| Lead | ²¹¹Pb | β | 36.1 minutes | |
| Astatine | ²¹⁵At | α | ~10⁻⁴ second | |
| Bismuth[16] | ²¹¹Bi | α (99.7%) and β (0.3%) | 2.15 minutes | |
| Polonium | ²¹¹Po | α | 0.25 second | |
| Thallium | ²⁰⁷Tl | β | 4.78 minutes | |
| Lead | ²⁰⁷Pb | — | Stable | |
The Uranium-235 Series
The Uranium (Uranium-238) Series proceeds like this:
| THE URANIUM-238 SERIES | |||
|---|---|---|---|
| Element | Symbol | Radiation | Half-life |
| Uranium | ²³⁸U | α | 4.51 × 10⁹ years |
| Thorium | ²³⁴Th | β | 24.1 days |
| Protactinium[17] | ²³⁴Pa | β | 1.18 minutes |
| Uranium | ²³⁴U | α | 2.48 × 10⁵ years |
| Thorium | ²³⁰Th | α | 7.6 × 10⁴ years |
| Radium | ²²⁶Ra | α | 1.62 × 10³ years |
| Radon | ²²²Rn | α | 3.82 days |
| Polonium[18] | ²¹⁸Po | α (99.98%) and β (0.02%) | 3.05 minutes |
| Lead | ²¹⁴Pb | β | 26.8 minutes |
| Astatine | ²¹⁸At | α | 1.3 seconds |
| Bismuth[18] | ²¹⁴Bi | β (99.96%) and α (0.04%) | 19.7 minutes |
| Polonium | ²¹⁴Po | α | 1.6 × 10⁻⁴ second |
| Thallium | ²¹⁰Tl | β | 1.32 minutes |
| Lead | ²¹⁰Pb | β | 22 years |
| Bismuth[18] | ²¹⁰Bi | β (~100%) and α (~2 × 10⁻⁴%) | 5.0 days |
| Polonium | ²¹⁰Po | α | 138.4 days |
| Thallium | ²⁰⁶Tl | β | 4.30 minutes |
| Lead | ²⁰⁶Pb | ... | Stable |
The Uranium-238 Series