Radioactive Disintegration Series: Definition, Examples

– In this subject, we will discuss the Radioactive Disintegration Series: Definition, Examples


– Several elements such as uranium and radium are unstable.

– Their atomic nucleus breaks off its own accord to form a smaller atomic nucleus of another element.

– The protons and neutrons in the unstable nucleus regroup to give the new nucleus.

– This causes the release of excess particles and energy from the original nucleus, which we call radiation.

– The elements whose atomic nucleus emits radiation are said to be radioactive.

– The spontaneous breaking down of the unstable atoms is termed radioactive disintegration or radioactive decay.

– The disintegration or decay of unstable atoms accompanied by emission of radiation is called Radioactivity

Radioactive Disintegration Series

– A radioactive element disintegrates by the emission of an α- or β- particle from the nucleus to form a new ‘daughter element’.

– This again disintegrates to give another ‘daughter element’.

– The process of disintegration and formation of a new element continues till a non-radioactive stable element is the product.

– The whole series of elements starting with the parent radioactive element to the stable end product is called a Radioactive Disintegration Series.

– Sometimes, it is referred to as a Radioactive Decay Series or simply a Radioactive Series.

– All the natural radioactive elements belong to one of the three series:

  • The Uranium Series
  • The Thorium Series
  • The Actinium Series

The Uranium Series

– It commences with the parent element uranium-238 and terminates with the stable element lead-206.

– It derives its name from uranium-238 which is the prominent member of the series and has the longest half-life.

– The Uranium series is illustrated in this Figure.

Radioactive Disintegration Series : Definition, Examples

The Thorium Series

– It begins with the parent element thorium-232 and ends with lead-208 which is stable.

– This series gets its name from the prominent member thorium-232.

The Actinium Series

– It starts with the radioactive element uranium-235.

– The end product is the stable element lead-207.

– This series derives its name from the prominent member actinium-227.

Radioactive Disintegration Series : Definition, Examples

The Neptunium Series

– This series consists of elements that do not occur naturally.

– It commences with neptunium-237 and terminates at bismuth-200.

– It derives its name from the prominent member neptunium-237.

Reference: Essentials of Physical Chemistry /Arun Bahl, B.S Bahl and G.D. Tuli / multicolor edition.

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