Atomic Theory Research

  • 200

    Democritus postulates theory of atoms and the void

    Democritus created the theory of Atoms and the Void. He believed that matter was made up of tiny, indivisible particles of different shapes and sizes. They floated around in an infinite nothingness called the void, repelling or attracting each other and colliding. *Date not specific. Circa. 460 BCE
  • Period: 200 to

    History of the Atomic Theory

  • Isaac Newton is knighted

    Isaac Newton devloped the laws of motion, and the laws of gravity. This would lead to later scientists defining the laws of physics.
  • Dalton proposes atomic theory

    Dalton proposes the atomic theory, with spherical, solid atoms based upon measurable properties of mass.
    *Date not specific
  • G.J. Stoney proposes the existence of electrons

    G.J. Stoney, an Irish scientist, proposes that electricity was made of negative particles called "electrons" *Date not specific
  • J.J Thompson confirms existence of electron

    Using cathode ray tubes, J.J Thompson, an English scientist, determines the existance of light particles that make up the atom. He confirms the existence of the electron. *Date not specific
  • Planck introduces the Quantum theory

    Planck, a German scientist, creates the Quantum theory. *Date not specific
  • Nagaoka creates a Saturn-like model of the atom.

    Nagaoka postules a Saturn-like model of the atom, with flat rings of electrons orbiting around a postively charged nucleus. *Date not specific
  • Milikan determines that mass and charge of an electron

    Using an oil drop experiment, Milikan, an American scientist, determines that mass and charge of an electron
  • E. Rutherford publishes his atomic theory

    E. Rutherford published his atomic theory that described the atom as mostly empty space which included a central nucleus positively charged orbited by negatively charged particles called electrons.
  • H.G.J Mosely determines the charges of the nuclei of most atoms

    Using x-ray tubes, H.G.J, Mosely determined the charges on the nuclei of most atoms. He found that the atomic number of an element is equal to the number of protons in the nucleus.
  • Bohr learns the chemical properties of matter depended on the electronic confirguration

    Bohr learned that chemical properties of matter depended on the frequency and arrangement of electrons around the nucleus. This meant that the elements on the periodic table should be arranged by number of electrons, rather than atomic weight, as previously thought.
  • James Chadwick discovers the neutron.

    In 1932, an English scientist named James Chadwick discovered the existance of the neutron.