Atomic Structure

What Atomic Structure covers

Atomic Structure is examined in Physics Paper 1. It covers the structure of an atom, mass number, atomic number and isotopes, from the plum pudding model to the nuclear model, Chadwick, the neutron, and comparing the models, radioactive decay and nuclear radiation, nuclear equations, half-lives and the random nature of radioactive decay, radioactive contamination, background radiation, uses of nuclear radiation, and how half-life affects hazard and nuclear fission and nuclear fusion.

The 11 subtopics

Each one has its own page.

• The structure of an atomThe radius of an atom and why atoms cannot be seen with a light microscope, the nucleus of protons and neutrons and its charge, electrons and their charge, the size of the nucleus and where the mass is concentrated, why an atom is mostly empty space, and how electrons sit in energy levels and move when an atom absorbs or emits electromagnetic radiation.Open →
• Mass number, atomic number and isotopesWhy an atom has equal numbers of electrons and protons and no overall charge, atomic number and mass number, working out the number of neutrons, reading the two numbers written before a chemical symbol, isotopes and how they differ, and how an atom becomes a positive ion by losing an outer electron.Open →
• From the plum pudding model to the nuclear modelWhy scientific models change, atoms as indivisible before the discovery of the electron, the plum pudding model, the alpha particle scattering experiment and its conclusions, why the plum pudding model could not explain the results, Bohr's electrons orbiting at specific distances, and the later discovery of protons in the nucleus.Open →
• Chadwick, the neutron, and comparing the modelsChadwick's evidence for the neutron, where it sits and why it was hard to detect, what the scattering results forced, and how the plum pudding and nuclear models differ.Open →
• Radioactive decay and nuclear radiationHow unstable nuclei decay, activity and its unit, count-rate and the detectors that measure it, the four kinds of nuclear radiation, what alpha particles, beta particles and gamma rays are, how strongly each ionises, what absorbs each and their ranges in air, and why smoke detectors use an alpha emitter.Open →
• Nuclear equationsWhat a nuclear equation represents, the two totals that balance, the numbers given to alpha and beta particles, and how each kind of emission changes mass number and atomic number.Open →
• Half-lives and the random nature of radioactive decayThe random nature of radioactive decay, half-life in terms of nuclei and of count-rate, why activity falls over time, finding a half-life from data and from a graph of count-rate against time, and why the background count is subtracted before a half-life is worked out.Open →
• Radioactive contaminationRadioactive contamination and where its hazard comes from, why the type of radiation matters and alpha emitters inside the body, irradiation and how it differs from contamination, comparing the hazards of sealed and loose sources, precautions such as lead-lined containers and protective clothing, and why findings on radiation effects are shared and peer reviewed.Open →
• Background radiationBackground radiation and why it cannot be escaped, its natural and man-made sources, why rocks, where a person lives and occupations such as flying change the dose received, radiation dose measured in sieverts and millisieverts, and converting and comparing doses.Open →
• Uses of nuclear radiation, and how half-life affects hazardHow widely half-lives vary and why very long and very short half-lives can each be hazardous, the problem of long-lived nuclear waste, medical tracers and the choice of isotope for them, treating tumours from several directions, evaluating radiation used to destroy tissue, and how the risk of medical radiation is perceived and judged.Open →
• Nuclear fission and nuclear fusionNuclear fission and the elements commonly used, spontaneous fission and absorbing a neutron to trigger it, the products and energy released and how that energy is used in a power station, chain reactions controlled in a reactor and uncontrolled in a nuclear weapon, nuclear fusion and its mass converted to energy, and how fusion and fission differ.Open →

What you need to know

Answer each one before you reveal it.

Take Atomic Structure further

The same content, four other ways.

Commonly confused

Pairs that lose marks when they are blurred together.

• Mass number vs Atomic number

  Mass number: the total of protons and neutrons in the nucleus. Atomic number: How many protons the nucleus of an element contains.

• Contamination vs Irradiation

  Contamination: unwanted presence of radioactive atoms on or in another material. Irradiation: Exposure of an object to nuclear radiation from an outside source.

• Nuclear fission vs Nuclear fusion

  Nuclear fission: the splitting of a large unstable nucleus into smaller nuclei. Nuclear fusion: The joining of two light nuclei to form a heavier nucleus.

Questions from this topic

Each one with the model answer underneath.

1. 1

   What is the approximate radius of an atom?

   Model answer

   About 1 × 10⁻¹⁰ m.

2. 2

   Explain why individual atoms cannot be seen using a light microscope.

   Model answer

   An atom has a radius of only about 1 × 10⁻¹⁰ m, which is far smaller than the wavelength of visible light.

3. 3

   Describe the basic structure of an atom.

   Model answer

   A positively charged nucleus made of protons and neutrons, surrounded by negatively charged electrons.

4. 4

   Which two types of particle are found in the nucleus of an atom?

   Model answer

   Protons and neutrons.

5. 5

   What is the overall charge on the nucleus of an atom, and why?

   Model answer

   It is positive, because it contains positively charged protons and neutrons that carry no charge.

6. 6

   Where in an atom are the electrons found?

   Model answer

   Surrounding the nucleus, outside it.

What is inside Levo

Six ways to work the same material.

Atomic Structure revision questions

What does Atomic Structure cover in AQA GCSE Physics?

11 subtopics: the structure of an atom, mass number, atomic number and isotopes, from the plum pudding model to the nuclear model, chadwick, the neutron, and comparing the models, radioactive decay and nuclear radiation, nuclear equations, half-lives and the random nature of radioactive decay, radioactive contamination, background radiation, uses of nuclear radiation, and how half-life affects hazard and nuclear fission and nuclear fusion. Each one has its own page with questions and model answers.

How is Atomic Structure organised?

By the AQA 8463 specification, subtopic by subtopic, so it matches the order you are taught it in.