The proton number of thorium is 90 and the proton number of radium is 88.
Which series of decays turns a thorium nucleus into a radium nucleus?
β−+α+β−+α\beta^- + \alpha + \beta^- + \alphaβ−+α+β−+α
α+α+α+β−\alpha + \alpha + \alpha + \beta^-α+α+α+β−
α+β−+β−+β−\alpha + \beta^- + \beta^- + \beta^-α+β−+β−+β−
α+α+α+β−+β−\alpha + \alpha + \alpha + \beta^- + \beta^-α+α+α+β−+β−
128 exam-style questions on AQA A Level Physics Radioactivity (A-level only), covering Rutherford scattering (A-level only), $\alpha$ , $\beta$ and $\gamma$ radiation (A-level only), Radioactive decay (A-level only), Nuclear instability (A-level only), Nuclear radius (A-level only), Mass and energy (A-level only), Induced fission (A-level only), and Safety aspects (A-level only). Each one has a worked solution and a mark scheme showing where the marks go.