100 Short Q&A for Atomic Structure (Class 11 NCERT) Part 1: Fundamental Particles and Early Models Q. No. Question Answer 1 Who discovered the electron? J. J. Thomson (using Cathode Ray Tube). 2 Who discovered the proton? E. Goldstein (using Canal Rays). 3 Who discovered the neutron? James Chadwick. 4 What is the charge-to-mass ratio (e/m) of an electron? 1.758820×1011 C/kg. 5 What is the charge of an electron? −1.602×10−19 Coulombs (Millikan's Oil Drop method). 6 What is the mass of a proton (in kg)? Approximately 1.672×10−27 kg. 7 What is an α-particle? A doubly positively charged helium nucleus (4He2+). 8 What did Thomson's model of the atom propose? A "Plum Pudding" or "Watermelon" model with embedded electrons. 9 What was the major observation of Rutherford's α-scattering experiment? Most α-particles passed straight through the gold foil. 10 What is the dense, central part of an atom called? The Nucleus. 11 What did Rutherford's model fail t...