NET, IAS, State-SET (KSET, WBSET, MPSET, etc.), GATE, CUET, Olympiads etc.: Atomic Structure

Get top class preparation for competitive exams right from your home: get questions, notes, tests, video lectures and more- for all subjects of your exam.

Atomic Structure

  • In 1809, Dalton suggested that atom is the smallest particle of the element and it is indivisible.
  • But in the beginning of 20th century Rutherford, J. J. Thomson and more suggested that atom is divisible and made up of electrically charged particles.

Electron

  • The electron is a fundamental particle of an atom which carries a unit negative charge.
  • It was discovered by J. J. Thomson in 1897.

Proton

  • It is a fundamental particle of an atom carrying a unit: positive charge.
  • It was discovered by Rutherford and Goldstein in 1886.

Neutron

  • It is a fundamental particle of an atom carrying no charge.
  • It was discovered by Chadwick in 1932.

Properties of Cathode Rays

  • They travel in straight: lines.
  • They cast shadow of solid objects placed in their path.
  • They cause mechanical motion, i.e.. , they consists of material particles.
  • They carry negative charge.
  • These rays are deflected when magnetic field is applied on them.
  • They produce heating effect.
  • They cause ionization of gas through which they pass.
  • They affect the photographic plates.
  • They have penetrating power.

Properties of Anode Rays

  • They travel in straight lines, however, their speed in much less than that of cathode rays.
  • They are made up of material particles.
  • They are positively charged.
  • They deflect in electric and magnetic field.

Properties of Nucleus

  • Nucleus of an atom consists of protons and neutrons, which are collectively known as nucleons.
  • Density of nucleus is enormous and is of order of 1014 g/cm.
  • Instability of the nucleus is due to high neutron proton ratio.