Describe an atom as a positively charged nucleus, consisting of protons and neutrons, surrounded by negatively charged electrons, with the nuclear radius much smaller than that of the atom and with almost all of the mass in the nucleus

Recall the typical size (order of magnitude) of atoms and small molecules

Describe the structure of nuclei of isotopes using the terms atomic (proton) number and mass (nucleon) number and using symbols in the format using symbols in the format

\(_6^{13}C\)

Recall that the nucleus of each element has a characteristic positive charge, but that isotopes of an element differ in mass by having different numbers of neutrons

Recall the relative masses and relative electric charges of protons, neutrons, electrons and positrons

Recall that in an atom the number of protons equals the number of electrons and is therefore neutral

Recall that in each atom its electrons orbit the nucleus at different set distances from the nucleus

Explain that electrons change orbit when there is absorption or emission of electromagnetic radiation

Explain how atoms may form positive ions by losing outer electrons

Recall that alpha, β– (beta minus), β+ (positron), gamma rays and neutron radiation are emitted from unstable nuclei in a random process

Recall that alpha, β– (beta minus), β+ (positron) and gamma rays are ionising radiations

Explain what is meant by background radiation

Describe the origins of background radiation from Earth and space

Describe methods for measuring and detecting radioactivity limited to photographic film and a Geiger–Müller tube

Recall that an alpha particle is equivalent to a helium nucleus, a beta particle is an electron emitted from the nucleus and a gamma ray is electromagnetic radiation

Compare alpha, beta and gamma radiations in terms of their abilities to penetrate and ionise

Describe how and why the atomic model has changed over time including reference to the plum pudding model and Rutherford alpha particle scattering leading to the Bohr model

Describe the process of β– decay (a neutron becomes a proton plus an electron)

Describe the process of β+ decay (a proton becomes a neutron plus a positron)

Explain the effects on the atomic (proton) number and mass (nucleon) number of radioactive decays (α, β, γ and neutron emission)

Recall that nuclei that have undergone radioactive decay often undergo nuclear rearrangement with a loss of energy as gamma radiation

Use given data to balance nuclear equations in terms of mass and charge

Describe how the activity of a radioactive source decreases over a period of time

Recall that the unit of activity of a radioactive isotope is the Becquerel, Bq

Explain that the half-life of a radioactive isotope is the time taken for half the undecayed nuclei to decay or the activity of a source to decay by half

Explain that it cannot be predicted when a particular nucleus will decay but half-life enables the activity of a very large number of nuclei to be predicted during the decay process

Use the concept of half-life to carry out simple calculations on the decay of a radioactive isotope, including graphical representations

Describe uses of radioactivity, including:

a) household fire (smoke) alarms
b) irradiating food
c) sterilisation of equipment
d) tracing and gauging thicknesses
e) diagnosis and treatment of cancer

Describe the dangers of ionising radiation in terms of tissue damage and possible mutations and relate this to the precautions needed

Explain how the dangers of ionising radiation depend on half-life and relate this to the precautions needed

Explain the precautions taken to ensure the safety of people exposed to radiation, including limiting the dose for patients and the risks to medical personnel

Describe the differences between contamination and irradiation effects and compare the hazards associated with these two

Compare and contrast the treatment of tumours using radiation applied internally or externally

Explain some of the uses of radioactive substances in diagnosis of medical conditions, including PET scanners and tracers

Explain why isotopes used in PET scanners have to be produced nearby

Evaluate the advantages and disadvantages of nuclear power for generating electricity, including the lack of carbon dioxide emissions, risks, public perception, waste disposal and safety issues

Recall that nuclear reactions, including fission, fusion and radioactive decay, can be a source of energy

Explain how the fission of U-235 produces two daughter nuclei and the emission of two or more neutrons, accompanied by a release of energy

Explain the principle of a controlled nuclear chain reaction

Explain how the chain reaction is controlled in a nuclear reactor, including the action of moderators and control rods

Describe how thermal (heat) energy from the chain reaction is used in the generation of electricity in a nuclear power station

Recall that the products of nuclear fission are radioactive

Describe nuclear fusion as the creation of larger nuclei resulting in a loss of mass from smaller nuclei, accompanied by a release of energy, and recognise fusion as the energy source for stars

Explain the difference between nuclear fusion and nuclear fission

Explain why nuclear fusion does not happen at low temperatures and pressures, due to electrostatic repulsion of protons

Relate the conditions for fusion to the difficulty of making a practical and economic form of power station