History of the Atomic Theory

By Menahil
  • 440

    Democritus

    Democritus
    In 440 B.C. Democritus, a Greek Philosopher hypotesized about all matter being able to be broken down into tiny invisble particles until they couldn't be broken down any further, but the idea wasnt popular because there wasn't any experimental evidence to support his theory.

  • John Dalton

    John Dalton
    In the 1800's Dalton reconsidered Democritus' thoery and reasoned that each element is composed of a different atom and came up with the basic atomic theory:
    1) All matter is broken down into particles called Atoms
    2) Atoms of different elements have different properties
    3) Atoms of different elements can be combined in ways to create new substances
    4) Atoms of the same element are identical in properties such as size/mass.

  • JJ Thompson

    JJ Thompson
    JJ Thomson theorized that atoms might be made of smaller, charged parts and that atoms must be made of both positive and negatives: Electrons (-) and Protons (+).

  • Ernest Rutherford

    Ernest Rutherford
    During his research of the atom, Rutherford conducted an experiment and discovered that inside the atom was a nucleus

  • Neils Bohr

    Neils Bohr
    In 1913, Neils Bohr discovered that the tiny particles (electrons) travelled in energy levels surrounding the nucleus and completed the model of the atom.

  • James Chadwick

    James Chadwick
    Rutherford's student, Chadwick discovered the neutron particles in the nucleus of an atom; neutrons are particles that are neutrally electric charged particles.