Atoms, nuclei & radiation
This is the story of what is really inside an atom, and what flies out of it when a nucleus is unstable. We begin with the alpha-particle scattering experiment and the nuclear (Rutherford) model it revealed — a tiny, dense, positive nucleus surrounded by mostly empty space. We then learn to describe any nucleus with proper nuclide notation, distinguishing the proton (atomic) number Z from the nucleon (mass) number A, and we meet isotopes. Next we study the three radiations — alpha, beta and gamma — their nature, penetration, ionising ability, and how they deflect in electric fields. Finally we treat radioactive decay as a random, spontaneous process and write fully balanced alpha, beta-minus and beta-plus decay equations term by term, meeting the antiparticle and the (anti)neutrino, and using conservation of nucleon number, proton number and energy.
By the end you should be able to (NSSCAS Physics (AS) 4.1):
- Describe and explain the simple structure of the nucleus (protons and neutrons held in a tiny, dense, positive core)
- Deduce, from the alpha-particle scattering experiment, the existence and small size of the nucleus, and describe the nuclear (Rutherford) model
- Distinguish between proton (atomic) number Z and nucleon (mass) number A, and use standard nuclide notation
- State that an element can exist in various isotopic forms, each with a different number of neutrons
- Recall the nature and properties of alpha, beta-minus, beta-plus and gamma radiation, including their penetration and ionising ability
- Recognise the effect of a uniform electric field on the paths of alpha and beta particles and gamma rays, and calculate the force on a charge using F = EQ with E = ΔV/Δd
- Recall that radioactive decay is the random and spontaneous emission of particles and/or electromagnetic radiation from an unstable nucleus
- Represent alpha, beta-minus and beta-plus decay by balanced equations, appreciating that nucleon number, proton number and energy are conserved
- State that (electron) antineutrinos and neutrinos are produced during beta-minus and beta-plus decay, and that beta particles are emitted with a range of kinetic energies
- Deduce the mass number and proton number of daughter and granddaughter products in a decay series