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Publish On: 2019-05-15

Andy More

Total Post: 752

Question: Explain briefly the natural radioactive series

Reply On: 2014-02-04

lala singh

Total Post: 22

ANS: Explain briefly the natural radioactive series

In experiments which followed the discovery of radioactivity, quite a number of substances were found to show activity. It was found that certain of these substances are associated with each other in series, the successive members with each other in series, the successive members being formed by the dissertation of the preceding member, Bering formed by the disintegration of the preceding member, until a stable nucleus is reached.

One can predict that there should exist four separate decay chains or radioactive series. A nucleus belong to one of four classes, depending on whether its mass number. A nucleus belongs to one of four classes, depending on whether its mass number A has the form 4n + 1, 4n + 2,or 4n + 3, where n an integer is. Radioactive decay of a nucleus in one of these will result in the formation of daughter nuclei in the same class. This follows, nice there is no change in mass number in β or in γ decay, while in α decay, ∆A = 4. the four radioactive series are represented. Each bears the name of its longest-lived element. The neptunium series is not observed naturally, because 93 Np237 (T = 2.2 × 106 year) has almost completely decayed since the formation of the elements (about 5 × 109 years ago).

The decay schemes of these four series end with stable isotopes of lead. A few heavy elements which do not belong to the radioactive isotopes which do not belong to the heavy-elements chains are found in nature:  

When the elements in a radioactive series are allowed to accumulate, a steady state will be reached (if the parent atom has a long half-life) in which the number N1 λ1 of atom of one isotope which decay per unit time is equal to the number N2 λ2 of atoms of the next isotope which decay per unit time, or N1 λ1 = N1 λ2 = N3 λ3 = ⋯ (equilibrium)

This equilibrium equation is often used to calculate λ for an isotope whose half-life is too large or too small to make a particle-counting experiment convenient.

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