GCSE Physics: Atomic & Radioactivity — Deep Revision Workbook

Inside GCSE Physics: Atomic & Radioactivity — Deep Revision Workbook

label the atom and its scale and order the atomic models, work with atomic number, mass number, isotopes and ions, sort the four types of nuclear radiation by penetration and ionising power, then calculate activity and half-life, balance decay numbers, tell contamination from irradiation and compare fission with fusion, before a full exam-style 6-mark question. About 45 minutes.

Learning objectives

• the atom, its size and the models — the nucleus and electrons, the atom (about 1×10⁻¹⁰ m) versus its nucleus (about 1×10⁻¹⁴ m), and the plum-pudding → Rutherford → Bohr development;
• atomic number, mass number, isotopes and ions — counting protons, neutrons and electrons, and telling isotopes from ions;
• the four types of nuclear radiation — alpha, beta, gamma and neutron, their penetration through paper, aluminium and lead, and their ionising power;
• decay, activity, equations and half-life — activity in becquerel, the alpha and beta decay number rules, and whole-half-life calculations and ratios;
• irradiation, contamination and nuclear fission and fusion — the difference between irradiation and contamination, and splitting versus joining nuclei, with a full exam-style 6-mark question.

Activities in this book

1. Section 1 — The Atom, Its Size & the Models

   an atom has a tiny central nucleus of protons and neutrons, with electrons in shells (energy levels) around it. The atom is about 1×10⁻¹⁰ m across; the nucleus is about 1×10⁻¹⁴ m — around ten thousand times smaller — yet holds nearly all the mass. The model developed from plum pudding → Rutherford’s nuclear model (from alpha-particle scattering) → Bohr’s energy levels.

2. Section 2 — Atomic Number, Mass Number, Isotopes & Ions

   in nuclear notation the bottom number is the atomic number (number of protons) and the top number is the mass number (protons + neutrons). So neutrons = mass number − atomic number. Isotopes have the same protons but different neutrons. An ion is an atom that has lost or gained electrons, giving it an overall charge.

3. Section 3 — The Four Types of Nuclear Radiation

   four radiations to know: alpha = a helium nucleus (2 protons + 2 neutrons); beta = a fast electron from the nucleus; gamma = a high-energy electromagnetic wave; neutron = a neutral particle with the same mass as a proton. Penetration: alpha stopped by paper, beta by a few mm of aluminium, gamma only by thick lead or concrete. Ionising power runs the other way — alpha most, gamma least.

4. Section 4 — Decay, Equations, Half-life & Fission/Fusion

   activity is the number of decays per second, in becquerel (Bq). Alpha decay: mass number −4, atomic number −2. Beta decay: mass number unchanged, atomic number +1 (a neutron becomes a proton). Half-life is the time for the activity to halve. Contamination = radioactive atoms on or in an object; irradiation = exposure from an outside source. Fission = splitting a large nucleus; fusion = joining two light nuclei.

5. Section 5 — Extended Exam-Style 6-Marker

   a 6-mark question rewards clear, linked physics. Plan first: define half-life, count the half-lives to find the activity, use the alpha-decay number rules, and compare the danger of alpha inside and outside the body, then separate contamination from irradiation. Write in full sentences using the correct key terms, and give a number where you can.

Suggestions for teaching

• Label the atom first. Secure the nucleus, protons, neutrons and electrons, then use the sizes to show the nucleus is about ten thousand times smaller than the atom.
• Drill the numbers. Practise atomic number = protons and mass number = protons + neutrons until neutrons = mass number − atomic number is automatic.
• Sort the radiations. Rehearse alpha = helium nucleus, beta = fast electron, gamma = wave, neutron = neutral particle, alongside the paper / aluminium / lead penetration order and the ionising order.
• Balance the decays. Model alpha decay (mass number −4, atomic number −2) and beta decay (mass number unchanged, atomic number +1) on a nuclear equation.
• Halve, then halve again. Build half-life confidence by repeatedly halving the activity and by counting how many halvings fit a given drop.