When ₉₀Th²²⁸ transforms to ₈₃Bi²¹², the number of emitted α and β particles are respectively

Options

(a) 8 α,7 β
(b) 4 α,7 β
(c) 4 α,4 β
(d) 4 α,1 β

Correct Answer:

4 α,1 β

Explanation:

α-particle = ₂He⁴, β-particle = ₋₁β and Nucleus = zXᴬ

Change in A occurs only due to α-emission.

Change in A = 228 – 212 = 16

This change is due to 4 α.

Again change in Z = 90 – 83 = 7

Change in Z due to 4α = 8

.·. Change in Z due to β = 8 – 7 = 1

This is due to one β.

Hence particles emitted = 4α, 1β.