Decay Simulator: Thorium-212

General data

Radioactive decay series

• Thorium-212 31.7 ms
• Radium-208 1.11 s
• Radon-204 74 s · 87.0%
• Polonium-200 11.5 min · 62.6%
• Francium-208 58.6 s · 13.0%
• Astatine-204 9.2 min · 35.9%
• Bismuth-200 36.4 min · 57.0%
• Lead-196 37 min · 7.1%
• Thallium-196 1.84 h · 7.1%
• Mercury-196 stable · 7.1%
• Radon-208 24.28 min · 1.4%
• Polonium-204 3.518 h · 35.4%
• Lead-200 21.5 h · 57.2%
• Thallium-200 26.1 h · 57.2%
• Mercury-200 stable · 57.2%
• Astatine-208 1.63 h · 0.54%
• Bismuth-204 11.28 h · 35.2%
• Polonium-208 2.898 a · 0.54%
• Lead-204 stable · 35.7%

Rare branches (below 0.01%)

Rare branches are transformations that occur in fewer than 0.01% of decays, e.g. double beta decay or cluster emission. The nuclides they produce are practically absent from a sample, so they are hidden by default to keep the main path clear. In this series: branches - 2, nuclides - 5.

• Bismuth-208 3.68×10⁵ a · 2.2×10⁻⁵%
• Lead-208 stable · 2.2×10⁻⁵%
• Mercury-192 4.85 h · 2.1×10⁻⁶%
• Gold-192 4.94 h · 2.1×10⁻⁶%
• Platinum-192 stable · 2.1×10⁻⁶%

How to read the simulation

Grid: each pixel is one atom of the starting isotope. When an atom decays, the pixel takes the colour of the decay product - in decay series mode the product can decay further. The moment each atom decays is random, but the probability follows from the half-life, so after one T½ about half of the atoms remain, after two - about a quarter.

Chart N(t): what percentage of the sample atoms each nuclide makes up at a given moment. The line of the starting isotope falls (by half after each T½), the lines of stable products rise, and those of short-lived ones first rise, then fall.

Chart A(t): activity, i.e. the number of decays per second (becquerel, Bq). It depends on the number of atoms and on how fast they decay: for the same number of atoms, the shorter the T½, the higher the activity.

Simulation time runs faster (or slower) than real time - the time scale slider sets the multiplier. This way you can watch the decay of isotopes that live from fractions of a second to billions of years.

Well-known isotopes

• H-3 - Tritium - glowing watch hands, nuclear fusion fuel.
• C-14 - Radiocarbon dating.
• K-40 - Natural radioactivity - in bananas and in our bodies.
• Co-60 - Radiotherapy and radiation sterilization.
• I-131 - Thyroid treatment; Chernobyl fallout.
• Cs-137 - Long-lasting contamination after Chernobyl and Fukushima.
• Rn-222 - Radon in basements and mines.
• Ra-226 - The longest-lived isotope of radium - the element discovered by Marie and Pierre Curie in 1898.
• U-235 - Nuclear power plant fuel; start of the actinium series.
• U-238 - Age of the Earth; start of the uranium series.
• Pu-238 - Power source for space probes (Voyager, Curiosity rover).
• Am-241 - Ionization smoke detectors.