αβγ decay
Decay Series
Chain Reaction
Nuclear Energy
Nuclear reactors

The diagram shows a section of a periodic table.

A decay series reveals the changes resulting from radioactivity.

Unusable atoms tend to go through several transitions before attaining stability.

Decay series are named after the parent element.

A radioactive decay series may be represented as shown:

To help understand what a decay series means, view the following demonstration.

of a decay series

What is a decay series?
The concept of a decay series may best be illustrated by an example, like that of the uranium-radium series.

When uranium-238 decays by alpha emission, thorium-234 is formed.
Thorium-234 is a beta emitter and decays to form protactinium-234. Protactinium-234 in turn is a beta emitter and decays to form an isotope of uranium, called uranium-234.
Uranium-234 decays by alpha emission to form thorium-230, and this in turn decays by alpha emission to yield the isotope radium-226.
This process continues through five more alpha emissions and four more beta emissions until it reaches the end product, an isotope of lead (element 82), which is stable (non-radioactive).
The members of the series all share a common characteristic: their mass numbers can be expressed by the simple formula 4n + 2, in which n is a whole number.

What other series are there?
Other natural radioactive series are the thorium series, called the 4n series because the mass numbers of all its members are exactly divisible by four, and the actinium series, or 4n + 3 series.
The parent of the thorium series is the isotope thorium-232, and the actinium series begins with uranium-235. A fourth series, the 4n + 1 series, all the members of which are artificially radioactive, has in recent years been discovered.

Are radioactive decay series useful?
An interesting application of knowledge of radioactive elements is made in determining the age of rocks.