# Predict decay chain of a radioactive element

I know there are tables of decay chain of radioactive elements. Is there a way to predict the whole chain from the first radioactive element?

Use the Evaluated Nuclear Structure Data File; search "by decay" and put the nuclide you'd like to start with in "parent." This will also tell you half-lives and Q-values.

A few nuclides have multiple decay modes; for instance radon-221 usually beta-decays to francium-221, but alpha-decays to polonium-217 about 22% of the time. You may find other "forks in the road" depending on where you start.

You ask in a comment about U-235. You can go a little simpler by looking at the chart of nuclides, which lists decay modes:

• U-235: α
• Th-231: β
• Pa-231: α
• Ac-227: β 99% (neglect α 1%)
• Th-227: α
• Ra-223: α
• Ra-219: α
• Po-215: α
• Pb-211: β
• Bi-211: α 99.3% (neglect β 0.7%)
• Tl-207: β

That takes you to lead-207, which is stable (and makes up 22% of natural lead).

• hey thanks for the reply I understand there are table we can look up with the decay chains, but have we been able to model and predict sequence? – TongMasterFlex Nov 9 '15 at 15:56
• Modern nuclear models are able to predict the energy levels for different nuclides, and that tells you which decays are energetically allowed. In general nuclei with "too many" neutrons will $\beta^-$-decay, nuclei with "too few" neutrons will $\beta^+$-decay, and nuclei that are "too heavy" will $\alpha$-decay. However the details are nontrivial, especially in the no-mans-land of unstable nuclei between lead and thorium. – rob Nov 10 '15 at 4:31
• thanks for the reply, but are we able to predict the chain of decay say starting from the U-253 to Fe? – TongMasterFlex Nov 23 '15 at 20:45