Development of the model of the atom

• Scientists

  • John Dalton ( start of 19th Century )
  • JJ Thomson ( 1897 )
  • Ernest Rutherford ( 1909 )
  • Neils Bohr ( around 1911 )
  • James Chadwick ( around 1940 )
• John Dalton ( start of 19th C )

  • Atom first described as solid spheres
  • based his theory on the law of conservation of mass and law of constant composition
  • all matter of atoms are invisible
  • invisible Particle model
• JJ Thomson ( 1897 )

  • Plum pudding model
  • atom is a ball of charge with electrons scattered within it
  • electrons scattered around in a ball of positive charge
• Ernest Rutherford ( 1909 )

  • alpha scattering experiment
  • discovered that mass is concentrated at centre and nucleus is charged
  • most mass in the nucleus
  • most atoms = empty space
  • nuclear model
  • protons discovered
• Neil Bohr (around 1911 (1913))

  • theorised electrons were in shells orbiting the nucleus
  • Bohr model
• James Chadwick ( around 1940 (1932))

  • discovered neutrons in the nucleus