Radon-220 is radioactive and undergoes decay to polonium-216 by emitting an $\alpha$-particle. The decay equation is shown below. $^{220}_{86}\text{Rn} \rightarrow ^{216}_{84}\text{Po} + ^{4}_{2}\text{He}$. How many neutrons are present in the radon and polonium nuclei?
Physics 9702 · AS & A Level · Atoms, nuclei and radiation