Discovery of Electron, Proton and Neutron — Prelims Strategy

Prelims Strategy

To excel in NEET questions on the discovery of subatomic particles, a multi-pronged strategy is essential. Firstly, memorize the key facts: the name of the discoverer, the year of discovery, and the specific experiment for each particle (Electron: J.

J. Thomson, 1897, Cathode Ray Experiment; Proton: Goldstein/Rutherford, 1886/1919, Anode Ray/Gold Foil; Neutron: James Chadwick, 1932, Beryllium bombardment). Secondly, understand the experimental setups and key observations.

For cathode rays, remember their properties are independent of gas/electrode, they are negatively charged, and deflected by fields. For anode rays, remember their properties depend on the gas, they are positively charged.

For Chadwick's experiment, focus on the neutral, highly penetrating radiation. Thirdly, know the properties of each particle: exact charge, relative charge, exact mass, and relative mass (e.g., electron is $1/1837$ of H atom, proton/neutron are $approx 1$ amu).

Pay attention to units. For numerical problems, practice calculating $e/m$ ratios. For conceptual questions, focus on distinguishing between the properties of cathode rays and anode rays, and understanding the significance of each discovery.

Be wary of trap options that mix up discoverers, experiments, or properties between the particles. Always read the question carefully, especially words like 'INCORRECT' or 'EXCEPT'.