Atom is the smallest indivisible particle of the matter . Atom is made of electron , proton and neutrons .
PARTICLE |
ELECTRON |
PROTON |
NEUTRON |
Discovery |
Sir . J . J . Thomson |
Goldstein ( 1886 ) |
Chadwick ( 1932 ) |
|
( 1869 ) |
|
|
Nature of charge |
Negative |
Positive |
Neutral |
Amount of charge 1.6 x 10 -19 Coloumb 1.6 x 10 -19 Coloumb 0 |
Mass |
9.11 x 10 -31 kg |
1.672614 x 10 -27 kg 1.67492 x10 -27 kg |
Electrons were discovered using cathode ray discharge tube experiment .
Nucleus was discovered by Rutherford in 1911 .
Cathode ray discharge tube experiment : A cathode ray discharge tube madeof glass is taken with two electrodes . At very low pressure and high voltage , current starts flowing through a stream of particles moving in the tube fromcathode to anode . These rays were called cathode rays . When a perforatedanode was taken , the cathode rays struck the other end of the glass tube atthe fluorescent coating and a bright spot on the coating was developed
Results : a . Cathode rays consist of negatively charged electrons . b . Cathode rays themselves are not visible but their behavior can be observed with help of fluorescent or phosphorescent materials . c . In absence of electrical or magnetic field cathode rays travel in straight lines d . In presence of electrical or magnetic field , behaviour of cathode rays is similar to that shown by electrons e . The characteristics of the cathode rays do not depend upon the material of the electrodes and the nature of the gas present in the cathode ray tube .