Atomic Model Timeline

  • The Alchemists
    400

    The Alchemists

    Scientists thought that everything had to be made up of all f the four elements earth, air, fire, and water.
  • Plato
    400

    Plato

    Plato came up with the word elements in 400 BC. He also favored the four elements theory how everything was made up of four elements.
  • Democritus
    430

    Democritus

    His theory was that matter could not be divided into smaller and smaller pieces eventually the smallest possible piece would be obtained. He named the smallest piece of matter an atomos.
  • Robert Boyle

    Robert Boyle

    He believed that chemical experiments could demonstrate the truth of the corpuscularian philosophy.
  • Lavoisier

    Lavoisier

    He created the Law of Conversation of mass it states that matter can be changed from one form into another, mixtures can be separated or made, and pure substances can be decomposed, but the total amount of mass remains constant.
  • Dmitri Mendeleev

    Dmitri Mendeleev

    Mendeleev predicted the existence and properties of new chemical elements. When these elements were discovered, his place in the history of science was assured.
  • John Dalton

    John Dalton

    He found out that all elements are composed of atoms.
  • JJ Thomson

    JJ Thomson

    He provided the first hint that an atom is made of even smaller particles.
  • The Curies

    The Curies

    Discovered radium and polonium. They studied radio activity.
  • Albert Einstein

    Albert Einstein

    The speed of light in a vacuum was independent of the motion of all observers. This was the theory of special relativity.
  • Rutherford

    Rutherford

    He worked on an experiment where he fired a stream of tiny positively charged particles at a thin sheet of gold foil. Rutherford concluded that an atom had a small positively charged center that repelled his positively charged “bullets.”
  • Henry Mosely

    Henry Mosely

    Henry Moseley published the results of his measurements of the wavelengths of the X-ray spectral lines of a number of elements which showed that the ordering of the wavelengths of the X-ray emissions of the elements coincided with the ordering of the elements by atomic number.
  • Bohr

    Bohr

    His theory was that electrons move in orbits around the nucleus,pretty much like planets circle the sun. These orbits are located at certain distances from the nucleus.
  • Electron Cloud Model

    Electron Cloud Model