DISCOVERY OF ATOM

Structure of atom of Class 9

DISCOVERY OF ATOM

  • The idea of tiniest unit of matter (Anu and Parmanu) was propounded by maharishi Kanad in Vedic period in our country.
  • Democritus, a Greek philosopher also proposed that matter is made up of extremely small particles, the “atom”. The name atom comes from Greek language.
  •  John Dalton in 1808 published theory of atom assuming that atoms are the ultimate indivisible particles of matter.
  • Later the works of William Crookes (1878), J.J. Thomson (1897) and Goldstein proved that atom of any element contains smaller particles which are either positively charged or negatively charged.
  • Work of Rutherford and Neils Bohr confirmed that an atom consists of three subatomic particles, that are electrons, protons and neutrons.
  • ( It has been established that the central core of an atom consists of protons and neutrons and is commonly called nucleus. The electrons revolve around the nucleus.
  • The atom as a whole is electrically neutral as the number of protons in it, is equal to the number of electrons.

An element is a pure substance which cannot be subdivided into two or more new substances by any means.

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