Charge to mass ratio of an electron was determined by Thomson. The chargeto mass ratio of an electron as 1.758820 x 10 11 C kg-1
Charge on an electron was determined by R A Millikan by using an oil dropexperiment. The value of the charge on an electron is-1.6 x 10- 19 C.
The mass on an electron was determined by combining the results ofThomson’ s experiment and Millikan’ s oil drop experiment. The mass of anelectron was determined to be 9.1094 x 10- 31 kg.
Discovery of protons and canal rays: Modified cathode ray tube experiment was carried out which led to the discovery of protons.
Characteristics of positively charged particles: a. Charge to mass ratio of particles depends on gas from which these originate
b. The positively charged particles depend upon the nature of gas present in the cathode ray discharge tube
c. Some of the positively charged particles carry a multiple of fundamental of electrical charge.
d. Behaviour of positively charged particles in electrical or magnetic field is opposite to that observed for cathode rays
Neutrons were discovered by James Chadwick by bombarding a thin sheet of beryllium by α- particles. They are electrically neutral particles having a mass slightly greater than that of the protons.