Question

A thorium-232 nucleus decays by a series of alpha and beta emissions until it reaches actinium-228. How many alpha emissions and how many beta emissions occur in this series of decays?

_________alpha emissions

__________beta emissions

Answer 1

alpha emission decreases mass number by 4 and atomic number by 2

beta decay increases atomic number by 1

Here mass number decreases from 232 to 228

This is decrease in mass number by 4

So, there is 1 alpha emission

Atomic number of Thorium is 90

Atomic number of Actinium is 89

So, there is decrease is atomic number by 1 unit

Decrease of 2 would have been occurred by alpha decay. So, there must be 1 beta decay so that the overall decrease in atomic number is just 1

Answer:

1 alpha emissions

1 beta emissions