Radioactive Series: Thorium, Uranium, Actinium, and Neptunium Series

Table of Contents

The radioactive series also called as radioactive decay series is the series of elements obtained by successive disintegration of a parent radioactive element to a non-radioactive stable element. The series of elements obtained from 90Th-232, 92U-235, and 92U-239 are natural radioactive series, while the series obtained from artificially prepared 93Np-237 is called radioactive series.

When a radioactive element emits α or β particles, the new daughter elements are formed and may have unstable nuclei. The daughter element further disintegrates by emitting α and β particles forming new elements. The process of disintegration is continued until a non-radioactive stable element is obtained. Thus, the formation of the stable nucleus from a radioactive element is not a one-step process.

There are four series of radioactive elements.

  • Thorium (4n) Series
  • Uranium (4n+2) Series
  • Actinium (4n+3) Series
  • Neptunium (4n+1) Series

Thorium (4n) Series

It begins with the radioactive elements, Uranium-232 and ends with stable non-radioactive lead (Pb)-208. The mass number of all elements are integral multiple of 4.

Uranium (4n+2) Series

The parent element, uranium-238, is used as its starting parent radioactive elements which undergo disintegration and form lead-206 as its final stable component. Since the mass number of all elements in this series gives a remainder of 2 when divided by 4, it is called the (4n+2) series, where n is an integer. It possesses the longest half-life.

Actinium (4n+3) Series

The radioactive element uranium-235 converts into Lead-207, a stable element as the final product. Since the mass number of all elements in this series gives a remainder of 3 when divided by 4, it is called the (4n+3) series, where n is an integer.

Neptunium (4n+1) Series

The elements in this series are not found in nature. It begins with Bismuth-200 and terminates into stable neptunium-237. The mass number of all elements in this series gives a remainder of 1 when divided by 4, hence is called the (4n+1) series.

radioactive series

List of radioactive series

The various radioactive series with their starting element, end-stable elements, and the half-life is presented below:

SeriesName of SeriesStarting Radioactive ElementStable Non-Radioactive ElementHalf-life of Starting Element
4nThorium90Th-23282Pb-2081.3 ×1010 year
4n+1Neptunium94Pu-24183Bi-2094.5 ×109 year
4n+2Uranium92U-23882Pb-2067.1 ×108 year
4n+3Actinium92U-23982Pb-20713.2 year

Radioactive Series Video

References

radioactive series

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