In the case of thorium `(A=232 and Z=90)`, we obtain an isotope of lead `(A=208 and Z=82)` after some radioactive disintegrations. The number of `alpha`- and `beta`-particles emitted are, respectively,

Options

A. `alpha=3,beta=3`
B. `alpha=6,beta=4`
C. `alpha=6,beta=0`
D. `alpha=4,beta=6`

Answer

b

Explanation

Number of `alpha`-paticles emitted `=(232-208)/(4=6)`
Decreases in charege number due to `alpha`-emission `=12`
But actual decrease in charege number `=90-82=8`.
Clearly, four `beta`-particles are emitted.