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Topic Notes · Easy summaries with diagrams
Chapter 2 — Chapter 2 — Atomic Structure
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📘Easy summary
Discharge tube experiments (gas at very low pressure, very high voltage) showed atoms contain smaller particles. Cathode rays bent toward the positive plate and were deflected by magnets; J.J. Thomson (1897) found their mass/charge ratio — they are electrons. Goldstein (1886) found canal (anode) rays with a perforated cathode — positive ions; Rutherford (1917) showed the hydrogen nucleus (proton) is in all nuclei.
⭐Key points
- Negative particles bend toward the positive plate; positive toward the negative plate.
- A proton is 1836 times heavier than an electron.
- Electrons are subatomic particles of all elements.
- Canal-ray properties depended on the gas used.
🔬Diagram
🌿Real-life example
Hydrogen gas in the tube gives H⁺ ions (protons) as canal rays.
💡Exam tip
- Discharge tube discovered electrons and protons (MCQ ii).
✅Quick check
1. Cathode rays bend towards the:
2. Canal rays were discovered by:
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