Historical Development of the Atom

  • Democritus
    400 BCE

    Democritus

    • First person to use the term 'atom', meaning indivisible.- Stated that atoms are tiny solid bits of matter that make up everything in the world and are too small to be seen.
  • John Dalton

    John Dalton

    • Adapted Democritus' theory into the first ever atomic model
    • Theorised that atoms can neither be created or destroyed
  • JJ Thompson

    JJ Thompson

    • Discovered the electron
    • Used a cathode ray tube to conduct his experiment
    • Proposed the plum pudding model
  • Ernest Rutherford

    Ernest Rutherford

    • Disagreed with JJ Thompson
    • Set up the gold foil experiment, where he fired alpha particles at a gold foil where only some particles deflected.
    • Discovered the nucleus of the atom
  • Niels Bohr

    Niels Bohr

    • Developed Rutherford's model
    • Discovered that electrons travel in separate orbits around the nucleus.
    • Stated that the number of electrons in the outer orbit determines the properties of an element
  • Electron Cloud Model - Erwin Schrodinger

    Electron Cloud Model - Erwin Schrodinger

    • Proposed electron probability through wave function equations The Electron Cloud Model is still used to this day and is one of the most accurate atomic models
  • James Chadwick

    James Chadwick

    • Discovered neutrons
    • Explained that electrons can only exist in specific energy levels
    • Stated that electrons have definite orbits