Question 1

Who discovered the electron?

Accepted Answer

J.J. Thomson discovered the electron in 1897 using a cathode ray tube. He measured the charge-to-mass ratio of cathode rays and concluded that they consisted of negatively charged particles, which were later named electrons.

Question 2

Who discovered the proton through canal rays?

Accepted Answer

E. Goldstein in 1886 discovered the presence of new radiations in a gas discharge tube, known as canal rays, which led to the discovery of the positively charged particle called the proton.

Question 3

Who discovered the neutron?

Accepted Answer

James Chadwick discovered the neutron in 1932 by bombarding beryllium with alpha particles. He found neutral particles with a mass nearly equal to that of a proton.

Question 4

What is the charge of an electron?

Accepted Answer

The charge of an electron is taken as negative unity, specifically -1.6 × 10^-19 Coulombs, as determined by J.J. Thomson and later precisely measured by Robert Millikan.

Question 5

Which subatomic particle has zero electrical charge?

Accepted Answer

A neutron is a neutral subatomic particle present in the nucleus of an atom, having zero electrical charge and a mass approximately equal to that of a proton.

Structure of the Atom — NCERT Class 9 Science Important Questions & Revision Notes