Atomic Model Development

  • Aristotle
    384 BCE

    Aristotle

    Didn't believe in atomic theory. Thought everything was made up of the 4 'elements', fire, earth, water and air.
  • Democritus
    350 BCE

    Democritus

    Mentor was named Leucippus who had come up with atomic theory. Democritus adopted it and came up with the fact that atoms were indivisible.
  • Period: 322 BCE to

    Key scientist timeline

  • John Dalton

    John Dalton

    3 parts to his atomic theory
    -All mater is made up of atoms
    -Atoms are indivisible and indestructible
    -Compounds are formed by two or more different kinds of atoms
  • J.J Thomson

    J.J Thomson

    -Discovered the electron and it's negative charge
    - Discovered that there should have been positive charge in the nucleus to attract the electrons.
  • Philipp Lenard

    Philipp Lenard

    Described atoms as mostly empty space that are filled with fast moving dynamides
    Neutrally charged particles made up of heavy positive particles stuck to a light negative particle
  • Ernest Rutherford

    Ernest Rutherford

    -Performed an experiment where he fired positively charged alpha particles at a piece of gold foil
    - Found that a small number bounced back.
    -Found atoms were made up of a positively charged nucleus orbited by electrons.
  • Niels Bohr

    Niels Bohr

    Changed Rutherford's model and proposed that electrons can only travel in certain orbits.
  • James Chadwick

    James Chadwick

    Discovered the nucleus was made up of neutrons and protons