Atom

Atomic Timeline

By 242581
  • 460 BCE

    Democritus

    Democritus
    Democritus was a Greek philosopher.
    He discovered a theory that atoms are indivisible and indestructible.
    He did not initially perform any research or experiments prior to this discovery.

  • John Dalton

    John Dalton
    John Dalton was a British chemist and school teacher.
    He developed the theory that all elements are composed of tiny indivisible particles called atoms, and atoms of the same element are identical.

  • Eugen Goldstein

    Eugen Goldstein
    He discovered the positive charged subatomic particle, protons.
    He made his discovery by observing a cathode-ray tube and found rays traveling in the opposite direction to the anode-rays.

  • J.J Thomson

    J.J Thomson
    Sir Joseph John Thomson was a British physicist.
    He discovered the negative subatomic particle, electrons.
    He made this discovery by performing experiments that involved passing an electric current through gases at low pressure.

  • Robert Millikan

    Robert Millikan
    Robert Millikan was a physicist.
    He made his discovery in 1908.
    He was initially able to measure the charge of an electron.
    He made his discovery by performing the oil drop experiment.
    He did this by dropping oil between electrodes. Robert Millikan measured the force of those droplets passing through the electric field. While measuring and calculating those quantities, they could determine the charge on a single electron.

  • Earnest Rutherford

    Earnest Rutherford
    Earnest Rutherford was a physicist.
    He made his discovery from 1909-1911.
    He discovered the atomic nucleus.
    He used a beam of positively charged helium particles aimed at a sheet of gold foil surrounded by a fluorescent screen.
    He eventually discovered that most of the particles passed through the foil with no deflection and deflected a couple of particles.

  • Neils Bohr

    Neils Bohr
    Neils Bohr was a Danish physicist.
    He discovered that His atomic model had a positively charged nucleus with negative electrons orbiting. Bohr worked with Rutherford to help create the Bohr model.

  • Erwin Schrodinger

    Erwin Schrodinger
    He discovered the electron cloud
    He developed mathematical equations to find the probability of electrons in a certain position.