History of the Atom

By BlakeH47
  • 405 BCE

    Democritis Discovers the atom

    The Greek philosopher Democritus introduced the idea of the atom. However, the idea was essentially forgotten for more than 2000 years, His ideal was that atoms were just indestructible particles in surrounded by empty space.

  • John Dalton's reintroduction of the Atom

    Experiments with gases that first became possible at the turn of the nineteenth century led John Dalton in 1803 to propose a modern theory of the atom based on the following assumptions.
    1. Matter is made up of atoms that are indivisible and indestructible.
    2. All atoms of an element are identical.
    3. Atoms of different elements have different weights and different chemical properties.
    4. Atoms of different elements combine in simple whole numbers
    5. Atoms cannot be created nor destroyed

  • J.J. Thompson and the discovery of the Electron

    J.J. Thompson and the discovery of the Electron
    During the 1880s and '90s, scientists searched cathode rays for the carrier of the electrical properties in matter. Their work lead up to the discovery by English physicist J.J. Thomson of the electron in 1897.

  • The plum pudding model

    The plum pudding model
    J.J. Thomson's experiments with cathode ray tubes showed that all atoms contain tiny negatively charged subatomic particles or electrons. Thomson proposed the plum pudding model of the atom, which had negatively-charged electrons embedded within a positively-charged "soup."

  • the Nucleus Ernest Rutherford

    the Nucleus Ernest Rutherford
    Rutherford used a beam of alpha particles aimed at a piece of gold foil. Most alpha particles passed through the foil, but a few were scattered backward and would hit a piece of tape that would light up. This showed that most of the atom is empty space surrounding a tiny nucleus.

  • the solar system Model

    the solar system Model
    Development of the Atomic Theory. In 1913, Neils Bohr, a student of Rutherford 's, developed a new model of the atom. He proposed that electrons are arranged in concentric circular orbits around the nucleus. This model is patterned on the solar system and is known as the planetary model.

  • Ernest rutherford and the proton

    Ernest rutherford and the proton
    A proton is a positively charged subatomic particle discovered by Ernest Rutherford in 1917. He proved that the nucleus of the hydrogen atom (i.e. a proton) is present in the nuclei of all other atoms. when his scintillation detectors detected hydrogen nuclei when a beam of alpha particles was shot into the air. After investigating further, Rutherford found that these hydrogen nuclei were produced from the nitrogen atoms present in the atmosphere.

  • quantum mechanics model

    quantum mechanics model
    In 1926, Schrodinger used the duality of electron wave particles to create and solve difficult mathematical formulas that accurately describe the behavior of electrons in a hydrogen atom.

  • The Neutron and James Chadwick

    The Neutron and James Chadwick
    In 1932, the physicist James Chadwick conducted an experiment in which he bombarded Beryllium with alpha particles from the natural radioactive decay of Polonium. The resulting radiation showed high penetration through a lead shield, which could not be explained with the particles known at that time.