Question

Who discovered the electron?  
1. J. J. Thomson
2. John Dalton
3. James Chadwick
4. Rutherford
5. None of the above/ More than one of the above.

Answer 1

Correct Answer - Option 1 : J. J. Thomson

The Correct answer is J. J. Thomson.

 

• A British physicist J.J.Thomsom Heightened the theory of Dalton.
• Thomson found the existence of extremely minute particles inside the atom.
• He compared the atom with a 'watermelon' in which the Red part resembles the positively charged portions while the black seed resembles the negatively charged electrons.
• The atom itself is neutral in nature, as it has equal positive and negative charged electrons.
• Thomson discovered 'Electrons' for which he got Nobel prize in 1906 A.D.
• Thomson proposed a better atomic theory than Dalton's atomic model.
• According to him, a positive charge is dispersed everywhere and the idea that atoms are made up of negative electrons embedded in a gel of positive charge was wrong.
• Electrons were accidentally discovered by J. J. Thomson while studying the cathode rays.
• The name electron was given by 'stony'.
• Cathode rays are emitted from the cathode in a straight line if these rays strike on metal objects there is the formation of 'X-rays'.

James Chadwick-

• Sir James Chadwick was awarded the 1935 Nobel Prize in Physics for his discovery of the neutron in 1932.
• By 1920, physicists knew that most of the mass of the atom was located in a nucleus at its center and that this central core contained protons.
• In May 1932 James Chadwick announced that the core also contained a new uncharged particle, which he called the neutron.

Rutherford-

• Rutherford overturned Thomson's atom model in 1911 with his well-known Gold Foil experiment.
• Rutherford made an experiment, he beamed alpha particles through a thin gold foil. From this, he came to know that:
  • Most alpha particles passed through the gold foil, very few particles bounced back exactly towards the source.
  • Some of the particles deviate at various angles.
  • He concluded that an atom has a tiny, dense, 'positively charged' core, where all mass is concentrated; known as Nucleus.
  • The thickness of gold foil - 0.00004 cm.
  • Alpha particle - A helium nucleus.

John Dalton-

• In 1803 A.D. he put forth his famous atomic theory.
  • The matter is made up of small particles called atoms.
  • Atoms can not be created, divided into smaller particles, nor destroyed in the chemical process.
  • Atom is a rigid and massive ball-like structure.