IGCSE Physics (0625) – Unit 5. Atomic physics-5.2.3 Radioactive decay Paper 2

Question

Some radioactive nuclei decay to give new nuclei which are also radioactive. Part of a series of  decays is shown.

$$
{ }_{92}^{238} \mathrm{U} \rightarrow{ }_{90}^{234} \mathrm{Th} \rightarrow{ }_{91}^{234} \mathrm{~Pa} \rightarrow{ }_{92}^{234} \mathrm{U} \rightarrow{ }_{90}^{230} \mathrm{Th} \rightarrow{ }_{88}^{226} \mathrm{Ra}
$$

 How many decays involve the emission of a -particle?

A 1

B 2

C 3

D 5