²²⁶₈₈Ra emits alpha and its daughter then emits beta-minus. (a) Write equations using X and Y for daughters. (b) Explain the beta-minus nuclear change. (c) Compare alpha, beta and gamma ionisation and penetration. (d) Explain why gamma changes neither proton nor nucleon number and why heating does not trigger decay.

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²²⁶₈₈Ra → ²²²₈₆X + ⁴₂He; ²²²₈₆X → ²²²₈₇Y + ⁰₋₁e + antineutrino. Conserve nucleon and proton numbers: alpha emission gives ²²⁶₈₈Ra → ²²²₈₆X + ⁴₂He. In beta-minus decay, a neutron becomes a proton while an electron and electron antineutrino are emitted: ²²²₈₆X → ²²²₈₇Y + ⁰₋₁e + anti-νₑ. Alpha is most ionising and least penetrating; beta is intermediate; gamma is least ionising per path length and most penetrating, requiring substantial shielding for reduction. Gamma is an energy photon with no proton or neutron, so nuclear numbers do not change. It can follow a decay that leaves an excited daughter. Radioactive decay is a spontaneous nuclear process. Ordinary heating changes atomic motion on energy scales far below nuclear transitions and does not schedule individual decays.

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