Physics · May / June 2020 · Paper 22 · Question 7

Radon-222 is an isotope of radon which undergoes a series of radioactive decays. Fig. 7.1 is a diagram showing the proton number (atomic number) and nucleon number (mass number) of nuclei involved in the series of decays. The point P represents a nucleus of radon-222. Starting at P, a nucleus of radon-222 decays to Q; then from Q to R; then from R to S; then from S to T; and finally from T to U. 210 82 84 proton number 86 212 214 216 218 nucleon number 220 222 P Q R T U S Fig. 7.1

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