Thorium `._(90)^(298)Bi` The produces a daughter nucleus that is radioactive. The augther in turn, produces it own radioactive daugher and so on. This process continues until bismuth `._(83)^(212)Bi` is reaches. What are the total number `N_(alpha)` of `alpha`-particle and the total number `N_(beta)` of `beta^(-)`-paricles that are generated in this series or radioactive decays?

Explanation

`._(90)^(228)Th rarr ._(83)^(212)Bi`
Decrease in mass number `= 228 - 212 = 16`
Number of `alpha`-particles = `4`
decrease in atomic number due to `alpha`-particles `= 8`
Actual decrease in atomic number `= 7`
i.e on e`beta^(-)` aprticle.