Correct Answer: J.J. Thomson
Subject: chemistry
Explanation: • <b>Key Fact</b> J.J. Thomson calculated the e/m specific charge of the electron, which is -1.76 × 10¹¹ C/kg. • <b>Supporting Detail</b> Robert Millikan conducted the Oil Drop Experiment to determine the absolute charge of the electron (-1.6 × 10⁻¹⁹ C). • <b>Related Concept</b> Once Thomson found ratio (e/m) and Millikan found charge (e), the exact mass of electron (m) was calculated algebraically. • <b>Why wrong options are wrong</b> Rutherford discovered nucleus, Chadwick discovered neutron. Millikan found charge, not e/m ratio. • <b>Exam Trick</b> "Thomson = Ratio (e/m)". "Millikan = Oil Drop (Charge 'e')". • <b>Additional Info</b> Thomson's discovery proved that atoms are divisible.
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