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This “Discovery of the Nucleus” PowerPoint lesson is designed for AQA GCSE Physics students, covering the historical development of atomic models, including Dalton’s, Thomson’s, Rutherford’s, Bohr’s, and Chadwick’s contributions. It provides detailed explanations, diagrams, and exam-style questions to help students understand how the modern nuclear model of the atom evolved through experiments and scientific discovery.

Students explore the evolution of atomic models, starting with Democritus, who first proposed that matter is made of indivisible particles (atomos), through to Dalton’s atomic theory, which stated that all matter is composed of identical atoms that combine in fixed ratios. The limitations of these models are discussed, including the discovery that atoms are not indivisible as first believed.

The lesson then introduces J.J. Thomson’s Plum Pudding Model, explaining his discovery of the electron in 1897 using the cathode ray tube experiment. Students analyze the strengths and weaknesses of this model, particularly how it failed to explain the structure of the positive charge in an atom.

The Rutherford Gold Foil Experiment is covered in detail, demonstrating how alpha particles were deflected at unexpected angles, leading to the discovery of the nucleus. Students learn that:

• Most alpha particles passed straight through, indicating atoms are mostly empty space.
• Some particles were deflected, suggesting a small, dense, positively charged nucleus at the center of the atom.
• A few particles bounced straight back, confirming the concentration of mass in the nucleus.

The Bohr Model is introduced, explaining how electrons exist in fixed energy levels (shells) instead of spiraling into the nucleus. Students analyze how energy is absorbed and emitted when electrons move between shells, leading to light emission in specific colors.

The lesson continues with James Chadwick’s discovery of the neutron, explaining how his beryllium experiment proved the existence of a neutral subatomic particle. This discovery helped explain isotopes and completed our modern understanding of atomic structure.

This editable PowerPoint (.pptx) file is fully aligned with the AQA GCSE Physics specification, offering clear explanations, historical context, practical applications, and exam-style practice. Updated in February 2025, this resource is perfect for building a strong conceptual understanding of atomic structure and the discovery of the nucleus in GCSE Physics.