Eduqas GCSE Physics
Eduqas GCSE Physics 9 Atomic Structure Exam Questions
Free Eduqas GCSE Physics revision for 9 Atomic Structure: what you need to know, common mistakes and exam-style questions with answers. Covers atomic models, isotopes, nuclear notation, alpha, beta and gamma radiation, decay equations, half-life, contamination, background radiation, fission and fusion.
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About Eduqas GCSE Physics 9 Atomic Structure
Atomic structure in Eduqas GCSE Physics has four parts: the nuclear atom and isotopes; absorption and emission of ionising radiations and of electrons and nuclear particles; hazards and uses of radioactive emissions and background radiation; and nuclear fission and fusion. You learn how the model of the atom developed, nuclear notation, the properties of alpha, beta and gamma radiation, how to balance nuclear decay equations and how to calculate half-life. You also compare contamination with irradiation, look at medical uses, and explain chain reactions in reactors and fusion in stars. Examiners regularly set decay equation, half-life and penetration questions and ask you to evaluate the risks of radiation.
What you need to know
- 9.1 Atomic models The plum pudding model was replaced by Rutherford's nuclear model after alpha particle scattering showed a tiny, dense, positive nucleus. Bohr placed electrons in fixed energy levels, and Chadwick discovered the neutron. Electron arrangements can change when atoms absorb or emit electromagnetic radiation.
- 9.1 Isotopes and notation Atomic number Z is the number of protons; mass number A is protons plus neutrons. Isotopes have the same number of protons but different numbers of neutrons. Atoms are about 10^-10 m across, the nucleus is roughly 10,000 times smaller, and almost all the mass is in the nucleus.
- 9.2 Types of radiation Alpha: helium nucleus, strongly ionising, stopped by paper or a few cm of air. Beta: fast electron from the nucleus, moderately ionising, stopped by a few mm of aluminium. Gamma: EM wave, weakly ionising, reduced by thick lead or concrete. Neutrons can also be emitted.
- 9.2 Decay equations and half-life Alpha decay reduces the mass number by 4 and atomic number by 2; beta decay increases the atomic number by 1 with no change in mass number; gamma changes neither. Half-life is the time for half the unstable nuclei, or the count rate, to fall by half.
- 9.3 Hazards and uses Contamination is unwanted radioactive material on or in an object; irradiation is exposure to radiation from outside. Background radiation comes from rocks, cosmic rays, food and medical sources. Short half-life isotopes are used as medical tracers; gamma rays are used to treat cancer.
- 9.4 Fission and fusion In fission a large nucleus such as uranium-235 absorbs a neutron and splits into two smaller nuclei, releasing energy and more neutrons, which can cause a chain reaction controlled by control rods. In fusion, light nuclei join to form a heavier nucleus, releasing energy, as in the Sun.
Common mistakes in 9 Atomic Structure
- Saying a nucleus disappears after one half-life. Half of the unstable nuclei decay in each half-life, so the activity halves; it never quite reaches zero.
- Confusing contamination and irradiation. Irradiation does not make an object radioactive; contamination means radioactive material is present on it.
- Saying beta particles come from the electron shells. A beta particle is a fast electron emitted from the nucleus when a neutron turns into a proton.
- Saying gamma radiation is the most dangerous in all situations. Inside the body alpha is the most dangerous because it is the most ionising; outside the body it is stopped by the skin.
- Mixing up fission and fusion. Fission splits large nuclei; fusion joins small nuclei.
Try three 9 Atomic Structure exam-style questions
1. A sample has a count rate of 800 counts per minute and a half-life of 2 hours. Calculate the count rate after 6 hours. (2 marks)
Show the mark scheme answer
6 hours = 3 half-lives; 800 → 400 → 200 → 100 counts per minute.
2. Uranium-238 (atomic number 92) decays by alpha emission to thorium (Th). Give the mass number and atomic number of the thorium nucleus. (2 marks)
Show the mark scheme answer
Mass number 238 - 4 = 234; atomic number 92 - 2 = 90.
3. Explain why a radioactive tracer injected into the body should emit gamma radiation and have a short half-life. (3 marks)
Show the mark scheme answer
Gamma can pass out of the body to be detected; gamma is weakly ionising so causes less damage; a short half-life means the activity falls quickly, reducing the patient's dose.
9 Atomic Structure FAQs
What does Eduqas GCSE Physics 9 Atomic Structure cover?
It covers models of the atom, isotopes and nuclear notation, alpha, beta and gamma radiation, decay equations and half-life, contamination and irradiation, background radiation, and nuclear fission and fusion.
Which paper is 9 Atomic Structure examined in?
It is examined in Component 1: Concepts in Physics (2 hours 15 minutes, 120 marks). Component 2: Applications in Physics can also test it through practical contexts and an unseen article.
What do I need to know about half-life for Eduqas GCSE Physics 9 Atomic Structure?
Be able to read the half-life from a decay graph, calculate how much activity remains after a whole number of half-lives, and explain why short half-life isotopes are chosen for medical tracers. Radioactive decay is random, so half-life describes the behaviour of large numbers of nuclei.
