Since radioactive disintegration is a continuous process hence a series can be drawn which is known as radioactive disintegration series. There are four such series:

(i) Thorium series (4n series) begins with $^{232}_{90}Th$ and ends at $^{208}_{82}Pb$. [Mass is fully divided by 4]

(ii) Neptunium series (4n + 1series) begains with $^{241}_{94}Pu \text{and ends at} ^{209}_{83}Bi$. [here reminder is one]

(iii) Uranium series (4n + 2 series) begins with $^{238}_{92}U \text{and ends at} ^{206}_{82}Pb$. [here reminder is 2]

(iv) Actinium series (4n + 3 series) begins with $^{235}_{92}U \text{and ends at}^{207}_{82}Pb$. [here reminder is 3]

Number of $\alpha, \beta$-particles emitted during these series.

 Series $\alpha$ $\beta$ 4n 6 4 (4n+1) 8 5 (4n+2) 8 6 (4n+3) 7 4

Neptunium series is an artificial series while rest are natural series.

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