Question

A radioactive nucleus ‘A’ undergoes a series of decays according to the following scheme:

The mass number and atomic number of A are 180 and 72 respectively. What are these numbers for A₄?

Answer 1

A has mass number as 180 and atomic number 172.

Formation of A₁ by α-decay:

Formation of A₂ by β decay:

Formation of A₄:

In r-decay, mass number and atomic number remain the same.

Thus,

Mass number of A₄ = 172

Atomic number of A₄­ = 169