Atomic Theory

  • 320


    Believed that all matter was composed of air wind fire and water
  • 350


    Democritus’ atomic model, , held that the physical world was made up of invisible, indivisible and indestructible atoms. While homogenous in individual composition, they can differ in shape, arrangement, position and weight.
  • Period: 460 to

    Alex Richards

  • Dalton

    Five main points of Dalton's atomic theory
  • Crooke

    When high voltage is applied to the tube, the electric field accelerates the small number of electrically charged ions always present in the gas, created by natural processes like radioactivity. These collide with other gas molecules, knocking electrons off them and creating more positive ions in a chain reaction. All the positive ions are attracted to the cathode or negative electrode. When they strike it, they knock large numbers of electrons out of the surface of the metal, which in turn are
  • John Newlands

    John Newlands
    John Newlands was the first person to devise a Periodic Table of elements arranged in order of their relative atomic weights
  • Medeleev

    First ever periodic table that was accurate and also left blank in certain places for the coming discovery of new elements.
  • JJ Thomson

    JJ Thomson
    discovered the electron in a series of experiments designed to study the nature of electric discharge in a high-vacuum cathode-ray tube, an area being investigated by numerous scientists at the time. Thomson interpreted the deflection of the rays by electrically charged plates and magnets as evidence of "bodies much smaller than atoms" that he calculated as having a very large value for the charge-to-mass ratio. Later he estim
  • Rutherford

    Ernest Rutherford put forth his atomic theory describing the atom as having a central positive nucleus surrounded by negative orbiting electrons. This model suggested that most of the mass of the atom was contained in the small nucleus, and that the rest of the atom was mostly empty space.
  • Bohr

    The Bohr model , depicts the atom as a small, positively charged nucleus surrounded by electrons that travel in circular orbits around the nucleus