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. [Figure 7.1]

1. (a)(i)State two points on Fig. 7.1 which represent isotopes of the same element.[1]
2. (a)(ii)Different isotopes of the same element have different atomic compositions. State how the composition of their atoms is different.[1]
3. (b)(i)A nucleus of radon-222 emits an alpha-particle as it decays. The radioactive decay of a single nucleus is random. Explain what is meant by the random radioactive decay of a nucleus.[1]
4. (b)(ii)In nuclide notation, radon-222 is written as 222Rn. When a nucleus of radon-222 emits an alpha-particle (α), it decays to an isotope of polonium (Po). Complete the decay equation below for this decay. 222Rn 86 → ..... Po + ..... α[2]
5. (c)(i)State the name of the particle emitted as a nucleus of R decays to a nucleus of S.[1]
6. (c)(ii)Describe the change in the composition of a nucleus of R as it decays to a nucleus of S.[2]

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