Radioactive decay and half-life

Learning objectives

Describe the nature, penetrating power and ionising ability of alpha particles, beta particles and gamma rays, and predict how each is deflected in an electric or a magnetic field

Construct balanced nuclear equations for alpha, beta-minus, beta-plus and gamma decay, applying conservation of nucleon number, proton number and charge, and identify the antineutrino or neutrino emitted in beta decay

Explain that radioactive decay is random and spontaneous, define half-life and activity with the becquerel as the unit of activity, and determine a half-life from a decay curve or from count-rate data corrected for background radiation

Interpret a graph of neutron number against proton number, explain the shape of the band of stability, and predict the likely decay mode of a nuclide from its position relative to that band

(HL) Apply the exponential decay law N = N₀e^(−λt) with A = λN, relate the decay constant to half-life through λ = ln2/T½, and obtain λ from the gradient of a graph of ln A against time

Describe the biological effects of ionising radiation and the precautions used to reduce exposure, and outline radiometric dating as an application of a known half-life