Subatomic particles: discovery of electron, proton, neutron
Atomic Structure · Chemistry
Study notes
Thomson measured e/m of cathode rays as 1.76 × 10¹¹ C/kg regardless of gas used. What did this prove? Step 1: Same e/m from different gases/metals → same particle from all matter. Step 2: Value huge compared to H⁺ ion → particle much lighter than any atom. Step 3: Deflected toward positive plate → negatively charged. Conclusion: electrons are universal, subatomic, negative constituents of all atoms.