Atomic Theory

By Nicole8toast
  • Period: 500 BCE to

    The Alchemists

    Believed that all metals were formed from two principles; mercury and sulfur.
  • 440 BCE

    Plato

    Plato
    Theorized that solid forms of matter were made up of indivisible elements.
  • 400 BCE

    Democritus

    Democritus
    Realized that if a stone was divided into two halves, both halves would have the same properties.

  • Robert Boyle

    Robert Boyle
    Believed that everything was composed of very tiny particles. This belief was called atomism.

  • Antone Lavoisier

    Antone Lavoisier
    Proposed the idea of substances just being an element on its own and not having been made up of other substances.

  • John Dalton

    John Dalton
    Believed that elements were made of particles called atoms and that they cannot be destroyed or created.

  • Amedeo Avogadro

    Amedeo Avogadro
    Suggested that equal volumes of gases at the same temperature and pressure contain the same number of molecules.

  • Dmitri Mendeleev

    Dmitri Mendeleev
    Believed that elements arranged according to the value of their atomic weight presents a clear periodicy of properties.

  • JJ Thomson

    JJ Thomson
    Discovered electrons. Also discovered that an atom can be separated and divided.

  • Pierre and Marie Curie

    Pierre and Marie Curie
    Suggested that powerful rays and energy, radium and polonium gave off were just particles from from tiny atoms.

  • Albert Einstein

    Albert Einstein
    Mathematically proved the existence of atoms and also proved that all liquids are made up of molecules.

  • Robert Milikan

    Robert Milikan
    Preformed the Milikan Oil Drop experiment which determined the size of electrons. It also determined that there was a smallest unit charge.

  • Ernest Rutherford

    Ernest Rutherford
    Believed that an atom is mostly empty space with electrons orbiting the nucleus.

  • Henry G. J. Mosley

    Henry G. J. Mosley
    Known for Mosely's Law. The Square root frequency of the x-ray emitted by an atom is equal to its atomic number.

  • Neils Bohr

    Neils Bohr
    Received a Nobel Prize for the Bohr model which shows positively charged nucleus surrounded by orbiting electrons.

  • Werner Heisenberg

    Werner Heisenberg
    Formulated a type of quantum mechanics based on matrices. He proposed the uncertainty relation, showing how precisely the position and velocity of a particle can be simultaneously determined.

  • James Chadwick

    James Chadwick
    Earned a Nobel prize for discovering neutrons in atoms.