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Rutherford’s model of atom

RELATED WORDS

  • (α)-particles
  • Gold foil
  • Planetary model of the atom
  • Nuclear atom
  • Rebounded
  • Nucleus
  • Well defined orbits
  • Helium ions

Definition of Rutherford’s model of atom

The Rutherford model is a model of the atom devised by Ernest Rutherford. Rutherford directed the famous Geiger-Marsden experiment and analysed and suggested the presence of nucleus in an atom

More About Rutherford’s model of atom

  • In this experiment, fast moving alpha (α)-particles were made to fall on a thin foil
  • Rutherford selected gold foil because he wanted a very thin foil. The gold foil that he selected was as thick as 1000 atoms
  • α particles are doubly charged helium ions. They have a considerable amount of energy as their mass is equal to 4u
  • It was expected that α-particles would be deflected by the sub-atomic particles in the gold atoms. Since the α-particles were much heavier than the protons, he did not expect to see large deflections
  • But most of the α particles passed straight through the gold foil
  • Some of the α particles were deflected by a small angle
  • One out of 12000 α particles rebounded
  • Rutherford concluded that most of the space inside the atom is empty because most of the α particles passed straight through the gold foil
  • Very few α particles were deflected by a small angle; hence a small portion of the atom consists of a positive charge
  • Few α particles rebounded, therefore, most of the mass and entire positive charge of the atom is concentrated at the centre of the atom called nucleus
  • A very small fraction of α particles were rebounded, so the mass and all the positive charge of the atom is concentrated at a very small portion of the atom
  • The radius of the nucleus is about times less than that of the atom
  • The conclusions of Rutherford are
  • There is a positively charged centre in the atom called “nucleus”. Nearly all the mass of the atom is concentrated at the nucleus
  • The electrons revolve around the nucleus in well defined orbits
  • The size of the nucleus is very small compared to the size of the atom

Applications

  • Results can best explained by a model for the atom as a tiny, dense, positively charged core called a nucleus, in which nearly all the mass is concentrated, around which the light, negative constituents, called electrons, circulate at some distance, much like planets revolving around the Sun
  • The Rutherford atomic model has been alternatively called the nuclear atom, or the planetary model of the atom
  • The electrostatic force of attraction between electrons and nucleus was likened to the gravitational force of attraction between the revolving planets and the Sun