Elementary Particles:

The particles which are structureless, indivisible and not regarded as made up of some other particles are called elementary particles.

History:

• 400 BC: Greek philosophers Democritus and Leucippus suggested that the matter is made of indivisible particles called atoms.
• 1804: Jhon Dalton found that atoms are the basic, indivisible building blocks of matter.
• 1897: J.J. Thomson discovered that atoms were fundamental constituent of all the matter.
• 1905: Einstein discovered the idea of quanta, the bundle of electromagnetic radiation.
• 1911: Thomson and Rutherford found that the atoms were not fundamental but have some internal structure.
• 1932: James Chadwick discovered the neutron.
• 1935: Yukawa proposed the stability of nucleus.

Nobel Prizes in Physics

Take reference from book. (2001 – 2022)

Some Important Particles:

1. Electron:

The first fundamental particle discovered by Thomson in 1897 is electron. It revolves round the nucleus of an atom in different permitted orbits. Its charge is [latex]-1.6 \times 10^{-19}[/latex] C and its mass is [latex]9.1 \times 10^{-31}[/latex] Kg. It is symbolized as –e.

2. Proton:

Proton was discovered by Rutherford in 1911. Its charge is [latex]+1.6 \times 10^{-19}[/latex] C and its mass is [latex]1.67 \times 10^{-27}[/latex] Kg. It is symbolized as p and is written as [latex]_1H^1[/latex].

3. Neutron:

Neutron was discovered by Chadwick in 1932. It has no charge. Its mass is [latex]1.67 \times 10^{-27}[/latex] Kg. It is symbolized as n and written as [latex]_0n^1[/latex].

4. Positron: