The isotope thorium-230 (²³⁰₉₀Th) decays by alpha particle (α-particle) emission.

1. (a)(i)Describe the composition of an α-particle.[1]
2. (a)(ii)State the name of the particle that is identical in composition to an α-particle.[1]
3. (b)(i)The α-particle decay of thorium-230 produces an isotope of radium. Deduce: the number of neutrons in a neutral atom of this isotope of radium number of neutrons = ........................................................[1]
4. (b)(ii)the number of electrons in a neutral atom of this isotope of radium. number of electrons = ........................................................[1]
5. (c)The half-life of thorium-230 is 75000 years. A radioactive sample contains 7.2 × 10¹⁶ thorium-230 atoms. Determine the time it takes for the number of thorium-230 atoms to decrease to 9.0 × 10¹⁵. time = ............................................................ years[3]
6. (d)(i)When it decays, thorium-230 also emits gamma radiation (γ-radiation). Fig. 8.1 shows a narrow beam of γ-radiation passing into an electric field. [Figure 8.1] On Fig. 8.1, sketch the path of the γ-radiation in the electric field.[1]
7. (d)(ii)Fig. 8.2 shows the electric field replaced with a magnetic field that is directed into the page. [Figure 8.2] On Fig. 8.2, sketch the path of the γ-radiation in the magnetic field.[1]

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